ASTM D7136/D7136M-20

Standard Test Method for Measuring the Damage Resistance of a Fiber-Reinforced Polymer Matrix Composite to a Drop-Weight Impact Event

SIGNIFICANCE AND USE
5.1 Susceptibility to damage from concentrated out-of-plane impact forces is one of the major design concerns of many structures made of advanced composite laminates. Knowledge of the damage resistance properties of a laminated composite plate is useful for product development and material selection.  
5.2 Drop-weight impact testing can serve the following purposes:  
5.2.1 To establish quantitatively the effects of stacking sequence, fiber surface treatment, variations in fiber volume fraction, and processing and environmental variables on the damage resistance of a particular composite laminate to a concentrated drop-weight impact force or energy.  
5.2.2 To compare quantitatively the relative values of the damage resistance parameters for composite materials with different constituents. The damage response parameters can include dent depth, damage dimensions, and through-thickness locations, F1, Fmax, E1, and Emax, as well as the force versus time curve.  
5.2.3 To impart damage in a specimen for subsequent damage tolerance tests, such as Test Method D7137/D7137M.  
5.3 The properties obtained using this test method can provide guidance in regard to the anticipated damage resistance capability of composite structures of similar material, thickness, stacking sequence, and so forth. However, it must be understood that the damage resistance of a composite structure is highly dependent upon several factors, including geometry, thickness, stiffness, mass, support conditions, and so forth. Significant differences in the relationships between impact force/energy and the resultant damage state can result due to differences in these parameters. For example, properties obtained using this test method would more likely reflect the damage resistance characteristics of an unstiffened monolithic skin or web than that of a skin attached to substructure which resists out-of-plane deformation. Similarly, test specimen properties would be expected to be similar to those of a ...
SCOPE
1.1 This test method determines the damage resistance of multidirectional polymer matrix composite laminated plates subjected to a drop-weight impact event. The composite material forms are limited to continuous-fiber reinforced polymer matrix composites, with the range of acceptable test laminates and thicknesses defined in 8.2.  
1.1.1 Instructions for modifying these procedures to determine damage resistance properties of sandwich constructions are provided in Practice D7766/D7766M.  
1.2 A flat, rectangular composite plate is subjected to an out-of-plane, concentrated impact using a drop-weight device with a hemispherical impactor. The potential energy of the drop-weight, as defined by the mass and drop height of the impactor, is specified prior to test. Equipment and procedures are provided for optional measurement of contact force and velocity during the impact event. The damage resistance is quantified in terms of the resulting size and type of damage in the specimen.  
1.3 The test method may be used to screen materials for damage resistance, or to inflict damage into a specimen for subsequent damage tolerance testing. When the impacted plate is tested in accordance with Test Method D7137/D7137M, the overall test sequence is commonly referred to as the Compression After Impact (CAI) method. Quasi-static indentation per Test Method D6264/D6264M may be used as an alternate method of creating damage from an out-of-plane force and measuring damage resistance properties.  
1.4 The damage resistance properties generated by this test method are highly dependent upon several factors, which include specimen geometry, layup, impactor geometry, impactor mass, impact force, impact energy, and boundary conditions. Thus, results are generally not scalable to other configurations, and are particular to the combination of geometric and physical conditions tested.  
1.5 Units—The values stated in either SI units or inch-poun...

General Information

• Status: Published
• Publication Date: 30-Sep-2020
• ICS: 83.120 - Reinforced plastics
• Technical Committee: D30 - Composite Materials
• Drafting Committee: D30.05 - Structural Test Methods

Relations

• Refers: ASTM D883-24 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2024
• Refers: ASTM D883-23 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2023
• Refers: ASTM D3763-23 - Standard Test Method for High Speed Puncture Properties of Plastics Using Load and Displacement Sensors
• Effective Date: 01-Nov-2023
• Refers: ASTM D2734-23 - Standard Test Methods for Void Content of Reinforced Plastics
• Effective Date: 01-Oct-2023
• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM D5229/D5229M-20 - Standard Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite Materials
• Effective Date: 01-Mar-2020
• Refers: ASTM D883-20 - Standard Terminology Relating to Plastics
• Effective Date: 01-Jan-2020
• Refers: ASTM D3878-19a - Standard Terminology for Composite Materials
• Effective Date: 15-Oct-2019
• Refers: ASTM D883-19c - Standard Terminology Relating to Plastics
• Effective Date: 01-Aug-2019
• Refers: ASTM D3878-19 - Standard Terminology for Composite Materials
• Effective Date: 15-Apr-2019
• Refers: ASTM D883-19a - Standard Terminology Relating to Plastics
• Effective Date: 15-Apr-2019
• Refers: ASTM D883-19 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2019
• Refers: ASTM D883-18a - Standard Terminology Relating to Plastics
• Effective Date: 01-Dec-2018
• Refers: ASTM D883-18 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2018
• Refers: ASTM D3763-18 - Standard Test Method for High Speed Puncture Properties of Plastics Using Load and Displacement Sensors
• Effective Date: 01-Nov-2018

Overview

ASTM D7136/D7136M-20 is the internationally recognized standard test method for measuring the damage resistance of fiber-reinforced polymer matrix composite laminated plates subjected to a drop-weight impact event. Developed by ASTM, this standard provides a consistent approach to evaluating how composite materials withstand concentrated, out-of-plane impacts-a common hazard in various engineering applications. The method is essential for material selection, quality control, and product development in industries relying on advanced composite materials.

Key Topics

• Damage Resistance of Composites
  The standard focuses on quantifying how multidirectional, continuous-fiber reinforced polymer matrix composite plates respond to sudden, concentrated impacts. It measures damage resistance by evaluating parameters such as dent depth, damage size, and type of internal and external damage.

• Impact Testing Procedures

  • Utilizes a drop-weight device with a hemispherical striker tip.
  • Specifies protocols for both material screening and preparation of specimens for further damage tolerance tests.
  • Optional instrumentation can record force and velocity during the impact for more detailed analysis.

• Significance of Test Variables
  Test results are highly dependent on:

  • Plate geometry and stacking sequence
  • Material thickness and layup
  • Impactor geometry, mass, and drop height
  • Boundary conditions and support fixture properties

• Quantitative Comparisons Enables comparison of different material systems under controlled, identical conditions by measuring variables such as:

  • Dent depth and damage geometry
  • Energy absorption and force-time response
  • Damage to through-thickness locations

Applications

ASTM D7136/D7136M-20 has a broad range of practical applications:

• Product Development and Material Selection
  Provides engineers and designers with quantitative data to evaluate and select composite materials based on their damage resistance properties for various structural applications.

• Aerospace, Automotive, and Industrial Sectors
  Widely used to assess the suitability of fiber-reinforced polymer composites in aircraft panels, automotive components, wind turbine blades, sporting goods, and civil infrastructure.

• Damage Tolerance Assessment
  Often applied in conjunction with further test methods (such as ASTM D7137/D7137M for Compression After Impact) to determine residual strength of composites after impact.

• Quality Control and Research
  Ideal for benchmarking new material formulations and manufacturing processes, as well as for routine quality checks during composite panel fabrication.

Related Standards

ASTM D7136/D7136M-20 references several related ASTM standards and industry practices, including:

• ASTM D7137/D7137M: Test Method for Compressive Residual Strength Properties of Damaged Polymer Matrix Composite Plates
• ASTM D7766/D7766M: Practice for Damage Resistance Testing of Sandwich Constructions
• ASTM D6264/D6264M: Test Method for Measuring the Damage Resistance of a Fiber-Reinforced Polymer-Matrix Composite to a Concentrated Quasi-Static Indentation Force
• ASTM D883: Terminology Relating to Plastics
• ASTM D3878: Terminology for Composite Materials

Each of these standards complements D7136/D7136M for mechanical testing, terminology, test specimen preparation (ASTM D5687/D5687M), or verification of testing equipment (ASTM E4).

Practical Value

ASTM D7136/D7136M-20 is essential for anyone involved in the design, manufacture, or maintenance of composite structures. By providing a repeatable method for measuring damage resistance, it helps safeguard structural integrity, optimize material use, and drive innovation in composite applications. Consistent use of this test method facilitates reliable comparison across material systems and ensures compliance with industry best practices in fiber-reinforced polymer composite testing and impact resistance assessment.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7136/D7136M − 20
Standard Test Method for
Measuring the Damage Resistance of a Fiber-Reinforced
Polymer Matrix Composite to a Drop-Weight Impact Event
This standard is issued under the fixed designation D7136/D7136M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.5 Units—The values stated in either SI units or inch-
pound units are to be regarded separately as standard. The
1.1 This test method determines the damage resistance of
values stated in each system are not necessarily exact equiva-
multidirectional polymer matrix composite laminated plates
lents; therefore, to ensure conformance with the standard, each
subjected to a drop-weight impact event. The composite
system shall be used independently of the other, and values
material forms are limited to continuous-fiber reinforced poly-
from the two systems shall not be combined.
mer matrix composites, with the range of acceptable test
1.5.1 Within the text, the inch-pound units are shown in
laminates and thicknesses defined in 8.2.
brackets.
1.1.1 Instructions for modifying these procedures to deter-
1.6 This standard does not purport to address all of the
mine damage resistance properties of sandwich constructions
safety concerns, if any, associated with its use. It is the
are provided in Practice D7766/D7766M.
responsibility of the user of this standard to establish appro-
1.2 A flat, rectangular composite plate is subjected to an
priate safety, health, and environmental practices and deter-
out-of-plane, concentrated impact using a drop-weight device
mine the applicability of regulatory limitations prior to use.
with a hemispherical impactor. The potential energy of the
1.7 This international standard was developed in accor-
drop-weight, as defined by the mass and drop height of the
dance with internationally recognized principles on standard-
impactor, is specified prior to test. Equipment and procedures
ization established in the Decision on Principles for the
are provided for optional measurement of contact force and
Development of International Standards, Guides and Recom-
velocity during the impact event. The damage resistance is
mendations issued by the World Trade Organization Technical
quantified in terms of the resulting size and type of damage in
Barriers to Trade (TBT) Committee.
the specimen.
1.3 The test method may be used to screen materials for
2. Referenced Documents
damage resistance, or to inflict damage into a specimen for
2.1 ASTM Standards:
subsequent damage tolerance testing. When the impacted plate
D792 Test Methods for Density and Specific Gravity (Rela-
is tested in accordance with Test Method D7137/D7137M, the
tive Density) of Plastics by Displacement
overall test sequence is commonly referred to as the Compres-
D883 Terminology Relating to Plastics
sion After Impact (CAI) method. Quasi-static indentation per
D2584 Test Method for Ignition Loss of Cured Reinforced
Test Method D6264/D6264M may be used as an alternate
Resins
method of creating damage from an out-of-plane force and
D2734 TestMethodsforVoidContentofReinforcedPlastics
measuring damage resistance properties.
D3171 Test Methods for Constituent Content of Composite
1.4 The damage resistance properties generated by this test
Materials
method are highly dependent upon several factors, which
D3763 Test Method for High Speed Puncture Properties of
include specimen geometry, layup, impactor geometry, impac-
Plastics Using Load and Displacement Sensors
tor mass, impact force, impact energy, and boundary condi-
D3878 Terminology for Composite Materials
tions. Thus, results are generally not scalable to other
D5229/D5229M TestMethodforMoistureAbsorptionProp-
configurations, and are particular to the combination of geo-
erties and Equilibrium Conditioning of Polymer Matrix
metric and physical conditions tested.
Composite Materials
D5687/D5687M Guide for Preparation of Flat Composite
This test method is under the jurisdiction of ASTM Committee D30 on
Composite Materials and is the direct responsibility of Subcommittee D30.05 on
Structural Test Methods. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2020. Published November 2020. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2005. Last previous edition approved in 2015 as D7136/D7136M – 15. Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D7136_D7136M-20. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7136/D7136M − 20
Panels with Processing Guidelines for Specimen Prepara- shown within square brackets: [M] for mass, [L] for length, [T]
tion for time, [θ] for thermodynamic temperature, and [nd] for
D6264/D6264M Test Method for Measuring the Damage non-dimensional quantities. Use of these symbols is restricted
Resistance of a Fiber-Reinforced Polymer-Matrix Com- to analytical dimensions when used with square brackets, as
posite to a Concentrated Quasi-Static Indentation Force the symbols may have other definitions when used without the
D7137/D7137M Test Method for Compressive Residual brackets.
StrengthPropertiesofDamagedPolymerMatrixCompos- 3.2.2 dent depth, d [L], n—residual depth of the depression
ite Plates formed by an impactor after the impact event.
D7766/D7766M Practice for Damage Resistance Testing of
3.2.2.1 Discussion—The dent depth shall be defined as the
Sandwich Constructions maximum distance in a direction normal to the face of the
E4 Practices for Force Verification of Testing Machines specimen from the lowest point in the dent to the plane of the
E6 Terminology Relating to Methods of Mechanical Testing impacted surface that is undisturbed by the dent.
E18 Test Methods for Rockwell Hardness of Metallic Ma-
3.2.3 nominal value, n—a value, existing in name only,
terials
assigned to a measurable property for the purpose of conve-
E122 Practice for Calculating Sample Size to Estimate,With
nient designation.
Specified Precision, the Average for a Characteristic of a
3.2.3.1 Discussion—Tolerances may be applied to a nomi-
Lot or Process
nal value to define an acceptable range for the property.
E177 Practice for Use of the Terms Precision and Bias in
-2
3.2.4 recorded contact force, F [MLT ], n—the force ex-
ASTM Test Methods
erted by the impactor on the specimen during the impact event,
E456 Terminology Relating to Quality and Statistics
as recorded by a force indicator.
E2533 Guide for Nondestructive Testing of Polymer Matrix
3.2.5 striker tip, n—the portion or component of the impac-
Composites Used in Aerospace Applications
torwhichcomesintocontactwiththetestspecimenfirstduring
2.2 Military Standards:
the impact event.
CMH-17-3G Composite Materials Handbook, Volume
3—Polymer Matrix Composites Materials Usage, Design
3.3 Symbols:
and Analysis
A = cross-sectional area of a specimen
MIL-HDBK-728/1 Nondestructive Testing
C = specified ratio of impact energy to specimen thickness
E
MIL-HDBK-731A Nondestructive Testing Methods of
CV = coefficient of variation statistic of a sample population
Composite Materials—Thermography
for a given property (in percent)
MIL-HDBK-732A Nondestructive Testing Methods of
D = damage diameter (see Fig. 11)
Composite Materials—Acoustic Emission
d = dent depth
MIL-HDBK-733A Nondestructive Testing Methods of
E = potential energy of impactor prior to drop
Composite Materials—Radiography
E = absorbed energy at the time at which force versus time
MIL-HDBK-787A Nondestructive Testing Methods of
curve has a discontinuity in force or slope
Composite Materials—Ultrasonics
E = energy absorbed by the specimen during the impact
a
NASA Reference Publication 1092 Standard Tests for
event
Toughened Resin Composites, Revised Edition, July
E = actual impact energy (incident kinetic energy)
i
E = absorbed energy at the time of maximum recorded
max
contact force
3. Terminology
F = recorded contact force
3.1 Definitions—Terminology D3878 defines terms relating
F = recorded contact force at which the force versus time
to composite materials. Terminology D883 defines terms
curve has a discontinuity in force or slope
relating to plastics. Terminology E6 defines terms relating to
F = maximum recorded contact force
max
mechanical testing. Terminology E456 and Practice E177
g = acceleration due to gravity
define terms relating to statistics. In the event of a conflict
h = specimen thickness
between terms, Terminology D3878 shall have precedence
H = impactor drop height
over the other standards.
l = specimen length
3.2 Definitions of Terms Specific to This Standard:
m = impactor mass
3.2.1 Ifthetermrepresentsaphysicalquantity,itsanalytical
m = impactor mass for drop height calculation
d
dimensionsarestatedimmediatelyfollowingtheterm(orletter
m = impactor mass in standard gravity for drop height
dlbm
symbol) in fundamental dimension form, using the following
calculation
ASTM standard symbology for fundamental dimensions,
n = number of specimens per sample population
N = number of plies in laminate under test
S = standard deviation statistic of a sample population for
Available from SAE International (SAE), 400 Commonwealth Dr.,Warrendale, n-1
PA 15096-0001, http://www.sae.org.
a given property
Available from U.S. Army Materials Technology Laboratory, Watertown, MA
t = time during impactor drop and impact event
02471.
5 t = time of initial contact
i
Available from National Aeronautics and Space Administration (NASA)-
Langley Research Center, Hampton, VA 23681-2199. t = contact duration (total duration of the impact event)
T
D7136/D7136M − 20
NOTE 1—Clamp tip centered 0.25 in. from edge of cut-out.
FIG. 1 Impact Support Fixture (Inch-Pound Version)
NOTE 1—Clamp tip centered 6 mm from edge of cut-out.
FIG. 2 Impact Support Fixture (SI Version)
w = specimen width configuration; comparisons cannot be made between materials
v = impactor velocity unlessidenticaltestconfigurations,testconditions,andsoforth
v = impactor velocity at time of initial contact, t
are used.
i i
W = distance between leading edges of the two flag prongs
4.2 Optional procedures for recording impact velocity and
on velocity indicator
applied contact force versus time history data are provided.
x = test result for an individual specimen from the sample
i
population for a given property
4.3 Preferred damage states resulting from the impact are
x¯ = mean or average (estimate of mean) of a sample popu-
located in the center of the plate, sufficiently far from the plate
lation for a given property
edges such that the local states of stress at the edges and at the
δ = impactor displacement
impact location do not interact during the damage formation
event.
4. Summary of Test Method
4.1 A drop-weight impact test is performed using a
5. Significance and Use
balanced, symmetric laminated plate. Damage is imparted
5.1 Susceptibilitytodamagefromconcentratedout-of-plane
through out-of-plane, concentrated impact (perpendicular to
impact forces is one of the major design concerns of many
the plane of the laminated plate) using a drop weight with a
structures made of advanced composite laminates. Knowledge
hemispherical striker tip. The damage resistance is quantified
of the damage resistance properties of a laminated composite
in terms of the resulting size and type of damage in the
specimen. The damage response is a function of the test plate is useful for product development and material selection.
D7136/D7136M − 20
FIG. 3 Representative Rigid Base (Inch-Pound Version)
FIG. 4 Representative Rigid Base (SI Version)
5.2 Drop-weight impact testing can serve the following include dent depth, damage dimensions, and through-thickness
purposes:
locations, F , F , E , and E , as well as the force versus
1 max 1 max
5.2.1 To establish quantitatively the effects of stacking
time curve.
sequence, fiber surface treatment, variations in fiber volume
5.2.3 To impart damage in a specimen for subsequent
fraction, and processing and environmental variables on the
damage tolerance tests, such as Test Method D7137/D7137M.
damage resistance of a particular composite laminate to a
5.3 The properties obtained using this test method can
concentrated drop-weight impact force or energy.
provideguidanceinregardtotheanticipateddamageresistance
5.2.2 To compare quantitatively the relative values of the
capability of composite structures of similar material,
damage resistance parameters for composite materials with
different constituents. The damage response parameters can thickness,stackingsequence,andsoforth.However,itmustbe
D7136/D7136M − 20
FIG. 5 Impact Device with Cylindrical Tube Impactor Guide Mechanism
FIG. 6 Impact Device with Double Column Impactor Guide Mechanism
understood that the damage resistance of a composite structure force/energy and the resultant damage state can result due to
is highly dependent upon several factors, including geometry, differences in these parameters. For example, properties ob-
thickness, stiffness, mass, support conditions, and so forth. tained using this test method would more likely reflect the
Significant differences in the relationships between impact damage resistance characteristics of an unstiffened monolithic
D7136/D7136M − 20
FIG. 7 Drop-Weight Impact Test Specimen (Inch-Pound Version)
FIG. 8 Drop-Weight Impact Test Specimen (SI Version)
skin or web than that of a skin attached to substructure which equivalent length and width dimensions, in comparison to
resistsout-of-planedeformation.Similarly,testspecimenprop-
those of a panel significantly larger than the test specimen,
erties would be expected to be similar to those of a panel with
D7136/D7136M − 20
FIG. 9 Representative Impactor Force versus Time History
FIG. 10 Impactor Force versus Time History with Harmonic Resonance
which tends to divert a greater proportion of the impact energy generated a larger amount of internal damage for a given
into elastic deformation.
amountofexternaldamage,whencomparedwiththatobserved
for similar impacts using sharp striker tips.Alternative impac-
5.4 The standard impactor geometry has a blunt, hemi-
tors may be appropriate depending upon the damage resistance
spherical striker tip. Historically, for the standard laminate
characteristics being examined. For example, the use of sharp
configuration and impact energy, this impactor geometry has
D7136/D7136M − 20
FIG. 11 Measurement of Extent of Damage
striker tip geometries may be appropriate for certain damage unless identical test configurations, test conditions, and lami-
visibility and penetration resistance assessments. nate configurations are used.Therefore, all deviations from the
standard test configuration shall be reported in the results.
5.5 The standard test utilizes a constant impact energy
normalized by specimen thickness, as defined in 11.7.1. Some
6.2 Material and Specimen Preparation—Poormaterialfab-
testing organizations may desire to use this test method in
rication practices, lack of control of fiber alignment, and
conjunction with D7137/D7137M to assess the compressive
damage induced by improper specimen machining are known
residual strength of specimens containing a specific damage
causes of high material data scatter in composites in general.
state, such as a defined dent depth, damage geometry, and so
Important aspects of plate specimen preparation that contribute
forth. In this case, the testing organization should subject
to data scatter include thickness variation, out-of-plane
several specimens, or a large panel, to multiple low velocity
curvature, surface roughness, and failure to maintain the
impacts at various impact energy levels using this test method.
dimensions specified in 8.2.
A relationship between impact energy and the desired damage
parameter can then be developed. Subsequent drop weight
6.3 Specimen Geometry and Impact Location—The size,
impact and compressive residual strength tests can then be
shape,thickness,andstackingsequenceoftheplate,alongwith
performed using specimens impacted at an interpolated energy
the impact location, can affect the impact deformation and
level that is expected to produce the desired damage state.
damage formation behavior of the specimens significantly.The
degree of laminate orthotropy can strongly affect the damage
6. Interferences
formation. Results can be affected if the impact force is not
6.1 The response of a laminated plate specimen to out-of-
applied perpendicular to the plane of the laminated plate.
plane drop-weight impact is dependent upon many factors,
6.4 Support Fixture Characteristics—Results are affected
such as laminate thickness, ply thickness, stacking sequence,
by the support fixture cut-out dimensions, material, fixture
environment, geometry, impactor mass, striker tip geometry,
bending rigidity, and the rigidity of the surface that the support
impact velocity, impact energy, and boundary conditions.
Consequently, comparisons cannot be made between materials fixture is located upon. The location of the clamps, clamp
D7136/D7136M − 20
FIG. 12 Commonly Observed Damage Modes from Out-of-Plane Drop-Weight Impact
geometry, and the clamping force can affect the deformation of 6.8 Non-Destructive Inspection—Non-destructive inspec-
the specimen during impact. tion (NDI) results are affected by the particular method
utilized, the inherent variability of the NDI method, the
6.5 Impact Device Characteristics—Results are affected by
experience of the operator, and so forth.
the rigidity of the impact device, friction between the impactor
and guide(s) during the drop, impactor geometry, and impactor 6.9 Force F and absorbed energy E do not physically
1 1
mass. Errors can result if the test specimen and specimen represent the initiation of damage, as sub-critical matrix cracks
support fixture are not centered with respect to the impact and small delaminations may initiate at lower force and energy
device. values. Rather, F and E represent the initial value of force
1 1
and energy at which a change in the stiffness characteristics of
6.6 Force Oscillations—Force versus time histories typi-
the specimen can be detected, respectively.
cally contain many oscillations which may be introduced by
two primary sources. The first source is the natural frequency 6.10 The dent depth may “relax” or reduce with time or
(or frequencies) of the impactor, and is often referred to as upon exposure to different environmental conditions.
“impactor ringing.” The ringing may be more severe if the
6.11 Non-laminated, 3-D fiber-reinforced composites may
impactor components are not rigidly attached. The second
form damage through different mechanisms than laminates.
source of force oscillations is the flexural vibration of the
impacted specimen. The “ringing” oscillations generally occur 7. Apparatus
at higher frequencies than the oscillations generated by the
7.1 Micrometers and Calipers—A micrometer witha4to
specimen. The high-frequency ringing oscillations do not
8 mm[0.16to0.32 in.]nominaldiameterball-interfaceoraflat
typically represent an actual force transmitted to the specimen.
anvil interface shall be used to measure the specimen thick-
However, the oscillations caused by specimen motion are
ness. A ball interface is recommended for thickness measure-
actual forces applied to the specimen and should not be filtered
ments when at least one surface is irregular (for example, a
or smoothed. For both sources, the oscillations are typically
coarse peel ply surface which is neither smooth nor flat). A
excited during initial contact and during damage formation.
micrometer or caliper, with a flat anvil interface, shall be used
For further definition and examples of force oscillations, refer
for measuring length, width, and other machined surface
to Appendix X1 of Test Method D3763.
dimensions, as well as the dimensions for detected damage.
6.7 Impact Variables—Results are affected by differences in The accuracy of the instruments shall be suitable for reading to
thedropheight,impactvelocity,andimpactenergy.Resultsare within 1 % of the specimen dimensions. For typical specimen
also affected by wave propagation and vibrations in the geometries, an instrument with an accuracy of 60.0025 mm
specimen, impactor, impact device, and support fixture during [60.0001in.]isadequateforthethicknessmeasurement,while
the impact event. an instrument with an accuracy of 60.025 mm [60.001 in.] is
D7136/D7136M − 20
[12 in.], an impactor with a mass of 2.0 6 0.25 kg [4 6 0.5 lbm] shall be
adequate for measurement of length, width, and other ma-
used instead.
chined surface dimensions, as well as damage dimensional
measurements.
7.3.2 Guide Mechanism—Historical guide mechanisms in-
clude single cylindrical tubes through which a cylindrical
NOTE 1—For specimens intended to undergo subsequent residual
strength testing, instrument accuracies shall be consistent with the
impactor travels (Fig. 5), as well as double-column guides for
requirements of Test Method D7137/D7137M.
acrosshead-mountedimpactor(Fig.6).Theheightoftheguide
mechanism shall be sufficient to permit drop-weight testing for
7.2 Support Fixture—The impact support fixture, shown in
the impact desired energy level. For cylindrical drop tubes, the
Figs.1and2,shallutilizeaplateatleast20mm[0.75in.]thick
clearance between the impactor and tube inner diameter should
constructed from either aluminum or steel. The cut-out in the
not exceed 1 mm [0.03 in.]. Details of the guide mechanism
plate shall be 75 61mmby125 6 1 mm [3.0 6 0.05 in. by
geometry shall be noted. In all respects, guide friction shall be
5.0 6 0.05 in.]. The face of the plate shall be flat to within
negligible; otherwise, velocity measurements shall be required
0.1 mm [0.005 in.] in the area which contacts the test speci-
and impact energy calculations shall be based upon the
men.Guidingpinsshallbelocatedsuchthatthespecimenshall
measured velocity (Eq 4).
be centrally positioned over the cut-out. Four clamps shall be
7.3.3 Force Indicator—If utilized, the force indicator shall
used to restrain the specimen during impact. The clamps shall
haveaminimumholdingcapacityof1100N(200lbf).Thetips be in conformance with Practices E4 and Test Method D3763,
and shall be capable of indicating the impact force imparted to
of the clamps shall be made of neoprene rubber with a
durometer of 70-80 Shore A. The fixture shall be aligned to a the test specimen. This device shall be essentially free from
inertia-lag at the predicted impact velocity and shall indicate
rigidbaseusingboltsorclamps;arepresentativebasedesignis
shown in Figs. 3 and 4. the force with an accuracy over the force range(s) of interest to
within 61 % of the indicated value. The force indicator shall
NOTE 2—When impacted with the standard impactor (defined in 7.3.1)
at the standard energy level defined in 11.7.1, the standard specimen has be positioned such that at least 95 % of the impactor mass is
historically developed damage sizes less than half of the unsupported
located above it; the error in the force reading increases as the
specimen width (38 mm [1.5 in.]). Should the expected damage area
percentage of mass located above the load cell decreases.
exceed this size (such as in studies for barely visible impact damage, for
7.3.4 Velocity Indicator—The impact device may be instru-
example), it is recommended to examine alternative specimen and fixture
designs, such as NASA 1092, which are larger and can accommodate mentedtomeasurethevelocityoftheimpactoratagivenpoint
larger damage areas without significant interaction from edge support
before impact, such that the impact velocity may be calculated.
conditions.
Several approaches to velocity measurements are available,
and the selection of a particular method is dependent upon the
7.3 Impact Device—Representative drop-weight impact
desired measurement accuracy. One commonly used approach
testing devices are shown in Figs. 5 and 6.At a minimum, the
tovelocitymeasurementutilizesadouble-prongedflagsystem,
impact device shall include a rigid base, a drop-weight
in which the flags are used to obstruct a light beam between a
impactor, a rebound catcher, and a guide mechanism. The
photo-diode emitter and detector. The impact velocity is
rebound catcher is typically an inertially activated latch that
calculatedusingthemeasuredtimethelightbeamisobstructed
trips upon the initial impact, then catches the impactor on a
by each prong, as well as the time that an impact force is first
stop during its second decent. The rebound catcher must not
detected. The leading edges of the flag prongs are typically
affect the motion of the impactor until after the impactor has
separated by 3.0 to 10.0 mm [0.125 to 0.400 in.], and the
lost contact with the specimen after the initial impact. If such
system is positioned such that velocity measurement is com-
equipment is unavailable, rebound hits may be prevented by
pletedbetween3to6mm[0.13to0.25in.]verticallyabovethe
sliding a piece of rigid material (wood, metal, and so forth)
surface of the specimen. The required accuracy of the velocity
between the impactor and specimen, after the impactor re-
measurement system, and the associated method for verifying
bounds from the specimen surface after impact. More complex
the measurement accuracy, shall be specified by the test
devices may include latching and hoist mechanisms, stop
requestor.
blocksorshockabsorbers,andinstrumentationfordetermining
impactor velocity and impact force. The use of velocity and
NOTE 4—It is recommended that the test requestor specify the required
force instrumentation is recommended to provide additional
accuracy of the velocity measurement as a percentage of indicated value,
information about the impact event, but is not required. down to a fixed value below which use of a percentage is no longer
practicable.
7.3.1 Impactor—The impactor shall have a mass of 5.5 6
0.25 kg [12 6 0.5 lbm], and shall have a smooth hemispherical
7.4 Conditioning Chamber—When conditioning materials
striker tip with a diameter of 16 6 0.1 mm [0.625 6 0.005 in.] at non-laboratory environments, a temperature-/vapor-level
and a hardness of 60 to 62 HRC as specified in Test Methods
controlledenvironmentalconditioningchamberisrequiredthat
E18. Alternative impactors may be used to study relationships shall be capable of maintaining the required temperature to
between visible damage geometry (for example, dent depth,
within 63°C[65 °F] and the required relative humidity level
dent diameter) and the internal damage state. If a different to within 63 % RH. Chamber conditions shall be monitored
impactor is used as part of the testing, the shape, dimensions, either on an automated continuous basis or on a manual basis
and mass shall be noted and the results reported as non- at regular intervals.
standard.
7.5 Environmental Test Chamber—An environmental test
chamber is required for test environments other than ambient
NOTE 3—If the desired impact energy level cannot be achieved using
the standard impactor mass dropped from a height of at least 300 mm testing laboratory conditions. This chamber shall be capable of
D7136/D7136M − 20
TABLE 1 Recommended Layups for Various Nominal Cured Ply
maintaining the test specimen at the required test environment
Thicknesses, Unidirectional Tape
during the mechanical test. The test temperature shall be
Nominal Cured Ply Thickness
maintained within 63°C[65 °F] of the required temperature,
Ply Count Layup
Minimum, mm Maximum, mm
and the relative humidity level shall be maintained to within
[in.] [in.]
63 % RH of the required humidity level.
0.085 [0.0033] 0.10 [0.004] 48 [45/0/-45/90]
6S
0.10 [0.004] 0.13 [0.005] 40 [45/0/-45/90]
7.6 Data Acquisition Equipment—For simple drop-weight
5S
0.13 [0.005] 0.18 [0.007] 32 [45/0/-45/90]
4S
impact testing, no data acquisition equipment is required.
0.18 [0.007] 0.25 [0.010] 24 [45/0/-45/90]
3S
Equipment capable of recording force and velocity data is
0.25 [0.010] 0.50 [0.020] 16 [45/0/-45/90]
2S
required if those measurements are desired. If utilized, such 0.50 [0.020] 0.75 [0.030] 8 [45/0/-45/90]
S
equipment shall be in accordance with Annex A1, Minimum
Instrumentation Requirements, of Test Method D3763. The
natural frequency of the transducer-impactor assembly shall be
Fabric laminates containing satin-type weaves shall have
greater than 6 kHz, the analog-to-digital converter shall be
symmetric warp surfaces, unless otherwise specified and noted
8-bit or greater, the minimum sampling rate shall be 100 kHz,
in the report. Recommended layups for various nominal cured
and the data storage capacity shall be 1000 points or larger.
ply thicknesses are provided in Table 2. The laminated plate
layup is to be defined such that the 0° fiber orientation is
7.7 Dent Depth Indicator—The dent depth can be measured
aligned with the lengthwise (long) dimension.
using a dial depth gauge, a depth gauge micrometer, a
8.2.1.3 Alternative Stacking Sequences—Laminates fabri-
tripod-mounted depth gauge, or a properly calibrated displace-
cated using other layups or fiber orientations, or both, may be
ment transducer. The measuring probe
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7136/D7136M − 15 D7136/D7136M − 20
Standard Test Method for
Measuring the Damage Resistance of a Fiber-Reinforced
Polymer Matrix Composite to a Drop-Weight Impact Event
This standard is issued under the fixed designation D7136/D7136M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method determines the damage resistance of multidirectional polymer matrix composite laminated plates subjected
to a drop-weight impact event. The composite material forms are limited to continuous-fiber reinforced polymer matrix
composites, with the range of acceptable test laminates and thicknesses defined in 8.2.
1.1.1 Instructions for modifying these procedures to determine damage resistance properties of sandwich constructions are
provided in Practice D7766/D7766M.
1.2 A flat, rectangular composite plate is subjected to an out-of-plane, concentrated impact using a drop-weight device with a
hemispherical impactor. The potential energy of the drop-weight, as defined by the mass and drop height of the impactor, is
specified prior to test. Equipment and procedures are provided for optional measurement of contact force and velocity during the
impact event. The damage resistance is quantified in terms of the resulting size and type of damage in the specimen.
1.3 The test method may be used to screen materials for damage resistance, or to inflict damage into a specimen for subsequent
damage tolerance testing. When the impacted plate is tested in accordance with Test Method D7137/D7137M, the overall test
sequence is commonly referred to as the Compression After Impact (CAI) method. Quasi-static indentation per Test Method
D6264/D6264M may be used as an alternate method of creating damage from an out-of-plane force and measuring damage
resistance properties.
1.4 The damage resistance properties generated by this test method are highly dependent upon several factors, which include
specimen geometry, layup, impactor geometry, impactor mass, impact force, impact energy, and boundary conditions. Thus, results
are generally not scalable to other configurations, and are particular to the combination of geometric and physical conditions tested.
1.5 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in
each system mayare not benecessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be
used independently of the other. Combiningother, and values from the two systems may result in non-conformance with the
standard.shall not be combined.
1.5.1 Within the text, the inch-pound units are shown in brackets.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
This test method is under the jurisdiction of ASTM Committee D30 on Composite Materials and is the direct responsibility of Subcommittee D30.05 on Structural Test
Methods.
Current edition approved March 15, 2015Oct. 1, 2020. Published March 2015November 2020. Originally approved in 2005. Last previous edition approved in 20122015
as D7136/D7136M - 12.D7136/D7136M – 15. DOI: 10.1520/D7136_D7136M-15.10.1520/D7136_D7136M-20.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7136/D7136M − 20
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D792 Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement
D883 Terminology Relating to Plastics
D2584 Test Method for Ignition Loss of Cured Reinforced Resins
D2734 Test Methods for Void Content of Reinforced Plastics
D3171 Test Methods for Constituent Content of Composite Materials
D3763 Test Method for High Speed Puncture Properties of Plastics Using Load and Displacement Sensors
D3878 Terminology for Composite Materials
D5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite
Materials
D5687/D5687M Guide for Preparation of Flat Composite Panels with Processing Guidelines for Specimen Preparation
D6264/D6264M Test Method for Measuring the Damage Resistance of a Fiber-Reinforced Polymer-Matrix Composite to a
Concentrated Quasi-Static Indentation Force
D7137/D7137M Test Method for Compressive Residual Strength Properties of Damaged Polymer Matrix Composite Plates
D7766/D7766M Practice for Damage Resistance Testing of Sandwich Constructions
E4 Practices for Force Verification of Testing Machines
E6 Terminology Relating to Methods of Mechanical Testing
E18 Test Methods for Rockwell Hardness of Metallic Materials
E122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot or
Process
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E456 Terminology Relating to Quality and Statistics
E1309 Guide for Identification of Fiber-Reinforced Polymer-Matrix Composite Materials in Databases (Withdrawn 2015)
E1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases (Withdrawn 2015)
E2533 Guide for Nondestructive Testing of Polymer Matrix Composites Used in Aerospace Applications
2.2 Military Standards:
CMH-17-3G Composite Materials Handbook, Volume 3—Polymer Matrix Composites Materials Usage, Design and Analysis
MIL-HDBK-728/1 Nondestructive Testing
MIL-HDBK-731A Nondestructive Testing Methods of Composite Materials—Thermography
MIL-HDBK-732A Nondestructive Testing Methods of Composite Materials—Acoustic Emission
MIL-HDBK-733A Nondestructive Testing Methods of Composite Materials—Radiography
MIL-HDBK-787A Nondestructive Testing Methods of Composite Materials—Ultrasonics
NASA Reference Publication 1092 Standard Tests for Toughened Resin Composites, Revised Edition, July 1983
3. Terminology
3.1 Definitions—Terminology D3878 defines terms relating to composite materials. Terminology D883 defines terms relating to
plastics. Terminology E6 defines terms relating to mechanical testing. Terminology E456 and Practice E177 define terms relating
to statistics. In the event of a conflict between terms, Terminology D3878 shall have precedence over the other standards.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 If the term represents a physical quantity, its analytical dimensions are stated immediately following the term (or letter
symbol) in fundamental dimension form, using the following ASTM standard symbology for fundamental dimensions, shown
within square brackets: [M] for mass, [L] for length, [T] for time, [θ] for thermodynamic temperature, and [nd] for non-dimensional
quantities. Use of these symbols is restricted to analytical dimensions when used with square brackets, as the symbols may have
other definitions when used without the brackets.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from SAE International (SAE), 400 Commonwealth Dr., Warrendale, PA 15096-0001, http://www.sae.org.
Available from U.S. Army Materials Technology Laboratory, Watertown, MA 02471.
Available from National Aeronautics and Space Administration (NASA)-Langley Research Center, Hampton, VA 23681-2199.
D7136/D7136M − 20
3.2.2 dent depth, d [L], n—residual depth of the depression formed by an impactor after the impact event. The dent depth shall
be defined as the maximum distance in a direction normal to the face of the specimen from the lowest point in the dent to the plane
of the impacted surface that is undisturbed by the dent.
3.2.2.1 Discussion—
The dent depth shall be defined as the maximum distance in a direction normal to the face of the specimen from the lowest point
in the dent to the plane of the impacted surface that is undisturbed by the dent.
3.2.3 nominal value, n—a value, existing in name only, assigned to a measurable property for the purpose of convenient
designation. Tolerances may be applied to a nominal value to define an acceptable range for the property.
3.2.3.1 Discussion—
Tolerances may be applied to a nominal value to define an acceptable range for the property.
3.2.4 principal material coordinate system, n—a coordinate system with axes that are normal to the planes of symmetry inherent
to a material.
3.2.4.1 Discussion—
Common usage, at least for Cartesian axes (123,xyz, and so forth), generally assigns the coordinate system axes to the normal
directions of planes of symmetry in order that the highest property value in a normal direction (for elastic properties, the axis of
greatest stiffness) would be 1 or x, and the lowest (if applicable) would be 3 or z. Anisotropic materials do not have a principal
material coordinate system due to the total lack of symmetry, while, for isotropic materials, any coordinate system is a principal
material coordinate system. In laminated composites, the principal material coordinate system has meaning only with respect to
an individual orthotropic lamina. The related term for laminated composites is “reference coordinate system.”
-2
3.2.4 recorded contact force, F [MLT ], n—the force exerted by the impactor on the specimen during the impact event, as
recorded by a force indicator.
3.2.6 reference coordinate system, n—a coordinate system for laminated composites used to define ply orientations. One of the
reference coordinate system axes (normally the Cartesian x-axis) is designated the reference axis, assigned a position, and the ply
principal axis of each ply in the laminate is referenced relative to the reference axis to define the ply orientation for that ply.
3.2.5 striker tip, n—the portion or component of the impactor which comes into contact with the test specimen first during the
impact event.
3.3 Symbols:
A = cross-sectional area of a specimen
C = specified ratio of impact energy to specimen thickness
E
CV = coefficient of variation statistic of a sample population for a given property (in percent)
D = damage diameter (see Fig. 11)
d = dent depth
E = potential energy of impactor prior to drop
E = absorbed energy at the time at which force versus time curve has a discontinuity in force or slope
E = energy absorbed by the specimen during the impact event
a
E = actual impact energy (incident kinetic energy)
i
E = absorbed energy at the time of maximum recorded contact force
max
F = recorded contact force
F = recorded contact force at which the force versus time curve has a discontinuity in force or slope
F = maximum recorded contact force
max
g = acceleration due to gravity
h = specimen thickness
H = impactor drop height
l = specimen length
m = impactor mass
m = impactor mass for drop height calculation
d
m = impactor mass in standard gravity for drop height calculation
dlbm
n = number of specimens per sample population
N = number of plies in laminate under test
S = standard deviation statistic of a sample population for a given property
n-1
D7136/D7136M − 20
NOTE 1—Clamp tip centered 0.25 in. from edge of cut-out.
FIG. 1 Impact Support Fixture (Inch-Pound Version)
NOTE 1—Clamp tip centered 6 mm from edge of cut-out.
FIG. 2 Impact Support Fixture (SI Version)
t = time during impactor drop and impact event
t = time of initial contact
i
t = contact duration (total duration of the impact event)
T
w = specimen width
v = impactor velocity
v = impactor velocity at time of initial contact, t
i i
W = distance between leading edges of the two flag prongs on velocity indicator
x = test result for an individual specimen from the sample population for a given property
i
x¯ = mean or average (estimate of mean) of a sample population for a given property
δ = impactor displacement
4. Summary of Test Method
4.1 A drop-weight impact test is performed using a balanced, symmetric laminated plate. Damage is imparted through
out-of-plane, concentrated impact (perpendicular to the plane of the laminated plate) using a drop weight with a hemispherical
striker tip. The damage resistance is quantified in terms of the resulting size and type of damage in the specimen. The damage
response is a function of the test configuration; comparisons cannot be made between materials unless identical test configurations,
test conditions, and so forth are used.
D7136/D7136M − 20
FIG. 3 Representative Rigid Base (Inch-Pound Version)
FIG. 4 Representative Rigid Base (SI Version)
4.2 Optional procedures for recording impact velocity and applied contact force versus time history data are provided.
4.3 Preferred damage states resulting from the impact are located in the center of the plate, sufficiently far from the plate edges
such that the local states of stress at the edges and at the impact location do not interact during the damage formation event.
5. Significance and Use
5.1 Susceptibility to damage from concentrated out-of-plane impact forces is one of the major design concerns of many structures
D7136/D7136M − 20
FIG. 5 Impact Device with Cylindrical Tube Impactor Guide Mechanism
FIG. 6 Impact Device with Double Column Impactor Guide Mechanism
made of advanced composite laminates. Knowledge of the damage resistance properties of a laminated composite plate is useful
for product development and material selection.
5.2 Drop-weight impact testing can serve the following purposes:
D7136/D7136M − 20
FIG. 7 Drop-Weight Impact Test Specimen (Inch-Pound Version)
FIG. 8 Drop-Weight Impact Test Specimen (SI Version)
5.2.1 To establish quantitatively the effects of stacking sequence, fiber surface treatment, variations in fiber volume fraction, and
processing and environmental variables on the damage resistance of a particular composite laminate to a concentrated drop-weight
impact force or energy.
D7136/D7136M − 20
FIG. 9 Representative Impactor Force versus Time History
FIG. 10 Impactor Force versus Time History with Harmonic Resonance
5.2.2 To compare quantitatively the relative values of the damage resistance parameters for composite materials with different
constituents. The damage response parameters can include dent depth, damage dimensions, and through-thickness locations, F ,
F ,E , and E , as well as the force versus time curve.
max 1 max
5.2.3 To impart damage in a specimen for subsequent damage tolerance tests, such as Test Method D7137/D7137M.
D7136/D7136M − 20
FIG. 11 Measurement of Extent of Damage
5.3 The properties obtained using this test method can provide guidance in regard to the anticipated damage resistance capability
of composite structures of similar material, thickness, stacking sequence, and so forth. However, it must be understood that the
damage resistance of a composite structure is highly dependent upon several factors, including geometry, thickness, stiffness, mass,
support conditions, and so forth. Significant differences in the relationships between impact force/energy and the resultant damage
state can result due to differences in these parameters. For example, properties obtained using this test method would more likely
reflect the damage resistance characteristics of an unstiffened monolithic skin or web than that of a skin attached to substructure
which resists out-of-plane deformation. Similarly, test specimen properties would be expected to be similar to those of a panel with
equivalent length and width dimensions, in comparison to those of a panel significantly larger than the test specimen, which tends
to divert a greater proportion of the impact energy into elastic deformation.
5.4 The standard impactor geometry has a blunt, hemispherical striker tip. Historically, for the standard laminate configuration and
impact energy, this impactor geometry has generated a larger amount of internal damage for a given amount of external damage,
when compared with that observed for similar impacts using sharp striker tips. Alternative impactors may be appropriate depending
upon the damage resistance characteristics being examined. For example, the use of sharp striker tip geometries may be appropriate
for certain damage visibility and penetration resistance assessments.
5.5 The standard test utilizes a constant impact energy normalized by specimen thickness, as defined in 11.7.1. Some testing
organizations may desire to use this test method in conjunction with D7137/D7137M to assess the compressive residual strength
of specimens containing a specific damage state, such as a defined dent depth, damage geometry, and so forth. In this case, the
testing organization should subject several specimens, or a large panel, to multiple low velocity impacts at various impact energy
levels using this test method. A relationship between impact energy and the desired damage parameter can then be developed.
D7136/D7136M − 20
FIG. 12 Commonly Observed Damage Modes from Out-of-Plane Drop-Weight Impact
Subsequent drop weight impact and compressive residual strength tests can then be performed using specimens impacted at an
interpolated energy level that is expected to produce the desired damage state.
6. Interferences
6.1 The response of a laminated plate specimen to out-of-plane drop-weight impact is dependent upon many factors, such as
laminate thickness, ply thickness, stacking sequence, environment, geometry, impactor mass, striker tip geometry, impact velocity,
impact energy, and boundary conditions. Consequently, comparisons cannot be made between materials unless identical test
configurations, test conditions, and laminate configurations are used. Therefore, all deviations from the standard test configuration
shall be reported in the results.
6.2 Material and Specimen Preparation—Poor material fabrication practices, lack of control of fiber alignment, and damage
induced by improper specimen machining are known causes of high material data scatter in composites in general. Important
aspects of plate specimen preparation that contribute to data scatter include thickness variation, out-of-plane curvature, surface
roughness, and failure to maintain the dimensions specified in 8.2.
6.3 Specimen Geometry and Impact Location—The size, shape, thickness, and stacking sequence of the plate, along with the
impact location, can affect the impact deformation and damage formation behavior of the specimens significantly. The degree of
laminate orthotropy can strongly affect the damage formation. Results can be affected if the impact force is not applied
perpendicular to the plane of the laminated plate.
6.4 Support Fixture Characteristics—Results are affected by the support fixture cut-out dimensions, material, fixture bending
rigidity, and the rigidity of the surface that the support fixture is located upon. The location of the clamps, clamp geometry, and
the clamping force can affect the deformation of the specimen during impact.
6.5 Impact Device Characteristics—Results are affected by the rigidity of the impact device, friction between the impactor and
guide(s) during the drop, impactor geometry, and impactor mass. Errors can result if the test specimen and specimen support fixture
are not centered with respect to the impact device.
D7136/D7136M − 20
6.6 Force Oscillations—Force versus time histories typically contain many oscillations which may be introduced by two primary
sources. The first source is the natural frequency (or frequencies) of the impactor, and is often referred to as “impactor ringing.”
The ringing may be more severe if the impactor components are not rigidly attached. The second source of force oscillations is
the flexural vibration of the impacted specimen. The “ringing” oscillations generally occur at higher frequencies than the
oscillations generated by the specimen. The high-frequency ringing oscillations do not typically represent an actual force
transmitted to the specimen. However, the oscillations caused by specimen motion are actual forces applied to the specimen and
should not be filtered or smoothed. For both sources, the oscillations are typically excited during initial contact and during damage
formation. For further definition and examples of force oscillations, refer to Appendix X1 of Test Method D3763.
6.7 Impact Variables—Results are affected by differences in the drop height, impact velocity, and impact energy. Results are also
affected by wave propagation and vibrations in the specimen, impactor, impact device, and support fixture during the impact event.
6.8 Non-Destructive Inspection—Non-destructive inspection (NDI) results are affected by the particular method utilized, the
inherent variability of the NDI method, the experience of the operator, and so forth.
6.9 Force F and absorbed energy E do not physically represent the initiation of damage, as sub-critical matrix cracks and small
1 1
delaminations may initiate at lower force and energy values. Rather, F and E represent the initial value of force and energy at
1 1
which a change in the stiffness characteristics of the specimen can be detected, respectively.
6.10 The dent depth may “relax” or reduce with time or upon exposure to different environmental conditions.
6.11 Non-laminated, 3-D fiber-reinforced composites may form damage through different mechanisms than laminates.
7. Apparatus
7.1 Micrometers and Calipers—A micrometer with a 4 to 7 mm8 mm [0.16 to 0.28 in.] 0.32 in.] nominal diameter ball-interface
shall be used to measure the specimen thickness when at least one surface is irregular (such as the bag-side of a laminate). A
micrometer with a 4 to 7 mm [0.16 to 0.28 in.] nominal diameter ball interface or with or a flat anvil interface shall be used to
measure the specimen thickness when both surfaces are smooth (such as tooled surfaces). thickness. A ball interface is
recommended for thickness measurements when at least one surface is irregular (for example, a coarse peel ply surface which is
neither smooth nor flat). A micrometer or caliper, with a flat anvil interface, shall be used to measure the length and width of the
specimen,for measuring length, width, and other machined surface dimensions, as well as the dimensions for detected damage. The
accuracy of the instruments shall be suitable for reading to within 1 % of the samplespecimen dimensions. For typical specimen
geometries, an instrument with an accuracy of 60.0025 mm [60.0001 in.] is adequate for the thickness measurement, while an
instrument with an accuracy of 60.025 mm [60.001 in.] is adequate for the measurement of length, width, and damage
dimensionother machined surface dimensions, as well as damage dimensional measurements.
NOTE 1—For specimens intended to undergo subsequent residual strength testing, instrument accuracies shall be consistent with the requirements of Test
Method D7137/D7137M.
7.2 Support Fixture—The impact support fixture, shown in Figs. 1 and 2, shall utilize a plate at least 20 mm [0.75 in.] thick
constructed from either aluminum or steel. The cut-out in the plate shall be 75 6 1 mm by 125 6 1 mm [3.0 6 0.05 in. by 5.0
6 0.05 in.]. The face of the plate shall be flat to within 0.1 mm [0.005 in.] in the area which contacts the test specimen. Guiding
pins shall be located such that the specimen shall be centrally positioned over the cut-out. Four clamps shall be used to restrain
the specimen during impact. The clamps shall have a minimum holding capacity of 1100 N (200 lbf). The tips of the clamps shall
be made of neoprene rubber with a durometer of 70-80 Shore A. The fixture shall be aligned to a rigid base using bolts or clamps;
a representative base design is shown in Figs. 3 and 4.
NOTE 2—When impacted with the standard impactor (defined in 7.3.1) at the standard energy level defined in 11.7.1, the standard specimen has historically
developed damage sizes less than half of the unsupported specimen width (38 mm [1.5 in.]). Should the expected damage area exceed this size (such as
in studies for barely visible impact damage, for example), it is recommended to examine alternative specimen and fixture designs, such as NASA 1092,
which are larger and can accommodate larger damage areas without significant interaction from edge support conditions.
7.3 Impact Device—Representative drop-weight impact testing devices are shown in Figs. 5 and 6. At a minimum, the impact
device shall include a rigid base, a drop-weight impactor, a rebound catcher, and a guide mechanism. The rebound catcher is
typically an inertially activated latch that trips upon the initial impact, then catches the impactor on a stop during its second decent.
D7136/D7136M − 20
The rebound catcher must not affect the motion of the impactor until after the impactor has lost contact with the specimen after
the initial impact. If such equipment is unavailable, rebound hits may be prevented by sliding a piece of rigid material (wood,
metal, and so forth) between the impactor and specimen, after the impactor rebounds from the specimen surface after impact. More
complex devices may include latching and hoist mechanisms, stop blocks or shock absorbers, and instrumentation for determining
impactor velocity and impact force. The use of velocity and force instrumentation is recommended to provide additional
information about the impact event, but is not required.
7.3.1 Impactor—The impactor shall have a mass of 5.5 6 0.25 kg [12 6 0.5 lbm], and shall have a smooth hemispherical striker
tip with a diameter of 16 6 0.1 mm [0.625 6 0.005 in.] and a hardness of 60 to 62 HRC as specified in Test Methods E18.
Alternative impactors may be used to study relationships between visible damage geometry (e.g., (for example, dent depth, dent
diameter) and the internal damage state. If a different impactor is used as part of the testing, the shape, dimensions, and mass shall
be noted and the results reported as non-standard.
NOTE 3—If the desired impact energy level cannot be achieved using the standard impactor mass dropped from a height of at least 300 mm [12 in.], an
impactor with a mass of 2.0 6 0.25 kg [4 6 0.5 lbm] shall be used instead.
7.3.2 Guide Mechanism—Historical guide mechanisms include single cylindrical tubes through which a cylindrical impactor
travels (Fig. 5), as well as double-column guides for a crosshead-mounted impactor (Fig. 6). The height of the guide mechanism
shall be sufficient to permit drop-weight testing for the impact desired energy level. For cylindrical drop tubes, the clearance
between the impactor and tube inner diameter should not exceed 1 mm [0.03 in.]. Details of the guide mechanism geometry shall
be noted. In all respects, guide friction shall be negligible; otherwise, velocity measurements shall be required and impact energy
calculations shall be based upon the measured velocity (Eq 4).
7.3.3 Force Indicator—If utilized, the force indicator shall be in conformance with Practices E4 and Test Method D3763, and shall
be capable of indicating the impact force imparted to the test specimen. This device shall be essentially free from inertia-lag at
the predicted impact velocity and shall indicate the force with an accuracy over the force range(s) of interest to within 61 % of
the indicated value. The force indicator shall be positioned such that at least 95 % of the impactor mass is located above it; the
error in the force reading increases as the percentage of mass located above the load cell decreases.
7.3.4 Velocity Indicator—The impact device may be instrumented to measure the velocity of the impactor at a given point before
impact, such that the impact velocity may be calculated. Several approaches to velocity measurements are available, and the
selection of a particular method is dependent upon the desired measurement accuracy. One commonly used approach to velocity
measurement utilizes a double-pronged flag system, in which the flags are used to obstruct a light beam between a photo-diode
emitter and detector. The impact velocity is calculated using the measured time the light beam is obstructed by each prong, as well
as the time that an impact force is first detected. The leading edges of the flag prongs are typically separated by 3.0 to 10.0 mm
[0.125 to 0.400 in.], and the system is positioned such that velocity measurement is completed between 3 to 6 mm [0.13 to 0.25
in.] vertically above the surface of the specimen. The required accuracy of the velocity measurement system, and the associated
method for verifying the measurement accuracy, shall be specified by the test requestor.
NOTE 4—It is recommended that the test requestor specify the required accuracy of the velocity measurement as a percentage of indicated value, down
to a fixed value below which use of a percentage is no longer practicable.
7.4 Conditioning Chamber—When conditioning materials at non-laboratory environments, a temperature-/vapor-level controlled
environmental conditioning chamber is required that shall be capable of maintaining the required temperature to within 63°C
[65°F]63 °C [65 °F] and the required relative humidity level to within 63 %. 63 % RH. Chamber conditions shall be monitored
either on an automated continuous basis or on a manual basis at regular intervals.
7.5 Environmental Test Chamber—An environmental test chamber is required for test environments other than ambient testing
laboratory conditions. This chamber shall be capable of maintaining the test specimen at the required test environment during the
mechanical test. The test temperature shall be maintained within 63°C [65°F]63 °C [65 °F] of the required temperature, and the
relative humidity level shall be maintained to within 63 % RH of the required humidity level.
7.6 Data Acquisition Equipment—For simple drop-weight impact testing, no data acquisition equipment is required. Equipment
capable of recording force and velocity data is required if those measurements are desired. If utilized, such equipment shall be in
accordance with Annex A1, Minimum Instrumentation Requirements, of Test Method D3763. The natural frequency of the
transducer-impactor assembly shall be greater than 6 kHz, the analog-to-digital converter shall be 8-bit or greater, the minimum
sampling rate shall be 100 kHz, and the data storage capacity shall be 1000 points or larger.
D7136/D7136M − 20
7.7 Dent Depth Indicator—The dent depth can be measured using a dial depth gage,gauge, a depth gagegauge micrometer, a
tripod-mounted depth gage,gauge, or a properly calibrated displacement transducer. T
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