ASTM D8285/D8285M-19

Standard Practice for Compressive Properties of Tapered and Stepped Joints of Polymer Matrix Composite Laminates by Sandwich Construction Long Beam Flexure

SIGNIFICANCE AND USE
5.1 Flexure tests on flat sandwich panel construction may be conducted to determine facesheet scarf or step joint compressive strength.  
5.2 This practice is limited to obtaining the compressive strength of the sandwich panel scarf and step joint facesheets. Due to the curvature of the flexural test specimen when loaded, facesheet compression strength from this test may not be equivalent to the facesheet compression strength of sandwich structures subjected to pure edgewise (in-plane) compression.  
5.3 Factors that influence the compressive response and should therefore be reported include the following: materials (laminate facesheet, core, and adhesive); methods of material fabrication; methods of material preparation, including surface preparation prior to bonding, lay-up, specimen facesheet stacking sequence, and overall thickness; core geometry (cell size); core density; adhesive thickness; joint taper ratio or step length; ply overlap length; relative thickness and stiffness of parent and repair laminates; adhesive bond stiffness; specimen preparation; specimen conditioning; environment of testing; specimen alignment; speed of testing; time at temperature; void content; and volume percent reinforcement. Properties, in the test direction, which may be obtained from this practice, include the following:  
5.3.1 Ultimate compressive strength (based on the nominal repair material thickness), (Frcu).  
5.3.2 Ultimate running load per ply, (Nj).
Note 2: Concentrated forces on beams with thin facesheets and low density cores can produce results that are difficult to interpret, especially close to the failure point. Wider loading blocks and rubber pads may assist in distributing the forces.
Note 3: To ensure that simple sandwich beam theory is valid, a good rule of thumb for the four-point bending test is the support span length divided by the sandwich thickness should be greater than 20 (S/d > 20) with the ratio of repair material facesheet thickness to core...
SCOPE
1.1 This practice covers the procedure for determination of the compressive strength of a tapered or stepped bonded joint of polymer matrix composite materials. It is applicable to secondary bonded or co-bonded laminates with either unidirectional plies or woven fabric reinforcements. The materials to be bonded may be different systems. In the bondline, a separate adhesive material may or may not be used (example: adhesives may be used with a prepreg system or may not be used with a wet lay-up repair system). The range of acceptable test laminates and thicknesses are described in 8.2.7. The standard repair types are the same as for the tensile loading in Practice D8131/D8131M. While external patch repairs are not explicitly covered in this practice, these repairs could be tested as a non-standard specimen using this practice.  
1.2 This practice supplements Test Method D7249/D7249M for compressive loading of facesheet sandwich constructions by long beam flexure. Several important test specimen parameters (for example, joint length, ply overlaps, step depth, and taper ratio) are not mandated by this practice; however, these parameters are required to be specified and reported to support repeatable results.  
1.3 Unidirectional (0° ply orientation) composites as well as multi-directional composite laminates and fabric composites, can be tested.  
1.4 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 are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.  
1.4.1 Within the text, the inch-pound units are shown in brackets.  
1.5 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 esta...

General Information

• Status: Published
• Publication Date: 31-Aug-2019
• ICS: 83.140.20 - Laminated sheets
• Technical Committee: D30 - Composite Materials
• Drafting Committee: D30.09 - Sandwich Construction

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 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 D7249/D7249M-20 - Standard Test Method for Facesheet Properties of Sandwich Constructions by Long Beam Flexure
• Effective Date: 01-Feb-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 D7249/D7249M-18 - Standard Test Method for Facesheet Properties of Sandwich Constructions by Long Beam Flexure
• Effective Date: 01-Apr-2018
• Refers: ASTM D3878-18 - Standard Terminology for Composite Materials
• Effective Date: 01-Apr-2018

Overview

ASTM D8285/D8285M-19 is a standard practice developed by ASTM International for determining the compressive properties of tapered and stepped joints in polymer matrix composite laminates using sandwich construction long beam flexure tests. This standard focuses on testing the compressive strength of facesheet scarf or step joints, enabling a consistent approach to characterizing bonded joints typically found in the repair or assembly of composite sandwich structures. The procedure accommodates both unidirectional plies and woven fabric reinforcements, covers both secondary bonded and co-bonded laminates, and allows for the use or exclusion of adhesives.

Key Topics

• Compressive Strength Evaluation: The main objective is to obtain the compressive strength of facesheet joints like scarf or step joints in polymer matrix composite laminates via flexure tests.
• Suitable Materials: Applies to composite sandwich panels with unidirectional or multi-directional (including fabric) laminates, permitting bonded joints with or without separate adhesives.
• Specimen Preparation: Details critical factors such as material types (laminate, core, adhesive), methods of fabrication and preparation, surface treatment, stacking sequence, core geometry, and repair design.
• Test Parameters: Parameters such as joint length, ply overlap length, taper ratio, core density, adhesive thickness, and environmental conditioning must be reported to ensure repeatability and traceability.
• Testing Limitations: Compressive strength results from this flexural test may not precisely match those from pure edgewise compression due to specimen curvature under loading.
• Failure Modes: Identifies acceptable and unacceptable failure modes in test specimens to ensure data integrity.
• Units and Reporting: Supports both SI and inch-pound units. Each system must be used independently, and test results should specify units.

Applications

ASTM D8285/D8285M-19 is widely relevant in industries where composite materials and sandwich panel constructions are critical, such as:

• Aerospace and Aviation: Essential for qualifying and certifying repair methodologies for aircraft sandwich structures that use polymer matrix composites.
• Marine and Automotive: Used for ensuring the performance of bonded joints in lightweight composite panels subject to compressive loads.
• Wind Energy: Helps in the evaluation of repairs and structural joints in composite wind turbine blades.
• Manufacturing and Quality Assurance: Enables composite manufacturers and repair facilities to validate repair procedures and maintain compliance with industry standards.
• Research and Development: Facilitates the development of new composite repair techniques and adhesive systems, and supports comparative studies of different joint geometries.

Related Standards

For comprehensive mechanical and physical assessment of polymer matrix composites and sandwich constructions, ASTM D8285/D8285M-19 references and is complemented by several other ASTM standards:

• ASTM D7249/D7249M: Test Method for Facesheet Properties of Sandwich Constructions by Long Beam Flexure.
• ASTM D8131/D8131M: Practice for Tensile Properties of Tapered and Stepped Joints of Polymer Matrix Composite Laminates.
• ASTM D792: Test Methods for Density and Specific Gravity of Plastics by Displacement.
• ASTM D3171: Test Methods for Constituent Content of Composite Materials.
• ASTM E4: Practices for Force Verification of Testing Machines.
• ASTM E2533: Guide for Nondestructive Testing of Polymer Matrix Composites.

Practical Value

Adopting ASTM D8285/D8285M-19 provides a controlled and uniform approach to assess the performance of critical sandwich structure repairs and bonded joints in composite laminates. It ensures repeatability, comparability, and documentation quality for test results, supporting manufacturers, engineers, and regulatory bodies in making informed decisions about composite material integrity and repair compliance. By detailing influencing factors and mandatory reporting aspects, this standard enhances the reliability, traceability, and acceptance of data across the composites industry.

Keywords: ASTM D8285/D8285M-19, compressive properties, sandwich construction, polymer matrix composite laminates, flexure testing, scarf joint, step joint, bonded joints, composite repairs, material testing standard

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: D8285/D8285M − 19
Standard Practice for
Compressive Properties of Tapered and Stepped Joints of
Polymer Matrix Composite Laminates by Sandwich
Construction Long Beam Flexure
This standard is issued under the fixed designation D8285/D8285M; 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 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This practice covers the procedure for determination of
responsibility of the user of this standard to establish appro-
the compressive strength of a tapered or stepped bonded joint
priate safety, health, and environmental practices and deter-
of polymer matrix composite materials. It is applicable to
mine the applicability of regulatory limitations prior to use.
secondary bonded or co-bonded laminates with either unidi-
1.6 This international standard was developed in accor-
rectional plies or woven fabric reinforcements. The materials
dance with internationally recognized principles on standard-
to be bonded may be different systems. In the bondline, a
ization established in the Decision on Principles for the
separate adhesive material may or may not be used (example:
Development of International Standards, Guides and Recom-
adhesives may be used with a prepreg system or may not be
mendations issued by the World Trade Organization Technical
used with a wet lay-up repair system). The range of acceptable
Barriers to Trade (TBT) Committee.
test laminates and thicknesses are described in 8.2.7. The
standard repair types are the same as for the tensile loading in
2. Referenced Documents
Practice D8131/D8131M. While external patch repairs are not
2.1 ASTM Standards:
explicitly covered in this practice, these repairs could be tested
D792 Test Methods for Density and Specific Gravity (Rela-
as a non-standard specimen using this practice.
tive Density) of Plastics by Displacement
1.2 This practice supplementsTest Method D7249/D7249M
D883 Terminology Relating to Plastics
for compressive loading of facesheet sandwich constructions
D3171 Test Methods for Constituent Content of Composite
by long beam flexure. Several important test specimen param-
Materials
eters (for example, joint length, ply overlaps, step depth, and
D3878 Terminology for Composite Materials
taper ratio) are not mandated by this practice; however, these
D5229/D5229M TestMethodforMoistureAbsorptionProp-
parameters are required to be specified and reported to support
erties and Equilibrium Conditioning of Polymer Matrix
repeatable results.
Composite Materials
D7249/D7249M Test Method for Facesheet Properties of
1.3 Unidirectional (0° ply orientation) composites as well as
Sandwich Constructions by Long Beam Flexure
multi-directional composite laminates and fabric composites,
D8131/D8131M Practice for Tensile Properties of Tapered
can be tested.
and Stepped Joints of Polymer Matrix Composite Lami-
1.4 Units—The values stated in either SI units or inch-
nates
pound units are to be regarded separately as standard. The
E4 Practices for Force Verification of Testing Machines
values stated in each system are not necessarily exact equiva-
E6 Terminology Relating to Methods of Mechanical Testing
lents; therefore, to ensure conformance with the standard, each
E122 Practice for Calculating Sample Size to Estimate,With
system shall be used independently of the other, and values
Specified Precision, the Average for a Characteristic of a
from the two systems shall not be combined.
Lot or Process
1.4.1 Within the text, the inch-pound units are shown in
E177 Practice for Use of the Terms Precision and Bias in
brackets.
ASTM Test Methods
E456 Terminology Relating to Quality and Statistics
This practice is under the jurisdiction ofASTM Committee D30 on Composite
Materials and is the direct responsibility of Subcommittee D30.09 on Sandwich For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Construction. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Current edition approved Sept. 1, 2019. Published October 2019. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
D8285_D8285M-19. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8285/D8285M − 19
E2533 Guide for Nondestructive Testing of Polymer Matrix h —specimen nominal compressive side parent laminate
p
Composites Used in Aerospace Applications facesheet thickness as specified by the test requestor (nominal
ply thickness may be available from the relevant material
2.2 SAE Document:
specification)
CMH-17 Composite Materials Handbook-17 - Volume I
h —specimen nominal compressive side repair laminate
r
3. Terminology
facesheet thickness as specified by the test requestor (nominal
ply thickness may be available from the relevant material
3.1 Definitions—Terminology D3878 defines terms relating
specification)
to high-modulus fibers and their composites. Terminology
L—length of loading span
D883definestermsrelatingtoplastics.TerminologyE6defines
S—length of support span
terms relating to mechanical testing. Terminology E456 and
N—ultimate joint running force per ply
j
Practice E177 define terms relating to statistics. In the event of
n—number of specimens
a conflict between terms, Terminology D3878 shall have
n —number of repair laminate plies
r
precedence over the other Terminology standards.
P—maximum force carried by test specimen at failure
f
NOTE 1—If the term represents a physical quantity, its analytical
s —standard deviation statistic of a sample population for
n-1
dimensionsarestatedimmediatelyfollowingtheterm(orlettersymbol)in
a given property
fundamental dimension form, using the following ASTM standard sym-
w—specimen width
bology for fundamental dimensions, shown within square brackets: [M]
for mass, [L] for length, [T] for time, [θ] for thermodynamic temperature, xi —test result for an individual coupon from the sample
and[nd]fornon-dimensionalquantities.Useofthesesymbolsisrestricted
population for a given property
to analytical dimensions when used with square brackets, as the symbols
x¯—mean or average (estimate of mean) of a sample popu-
may have other definitions when used without the brackets.
lation for a given property
3.2 Definitions of Terms Specific to This Standard:
4. Summary of Practice
3.2.1 co-bonded (repair) facesheet, n—the co-bonded
facesheet is the facesheet that is bonded to the parent pre-cured
4.1 Tapered or Stepped Joint Compressive Strength—In
facesheet and cured in a second cure cycle.
accordance with Test Method D7249/D7249M, but using a
tapered or stepped joint facesheet configured specimen (Fig. 1
3.2.2 joint compressive strength, n—ultimate compressive
or Fig. 2), subjecting a long beam of sandwich construction to
forceexperiencedbythetestspecimenfacesheetdividedbythe
a bending moment normal to the plane of the sandwich, using
initial width of the joint area and the nominal thickness of the
a 4-point loading fixture. Deflection and strain versus force
parent facesheet.
measurements are recorded.
3.2.3 nominal value, n—a value, existing in name only,
assigned to a measureable property for the purpose of conve- 4.2 The only acceptable failure modes for sandwich
nient designation. facesheet compressive strength are those which are internal to
the compressive loaded facesheet. Failure of the sandwich
3.2.3.1 Discussion—Tolerances may be applied to a nomi-
core, the core-to-facesheet bond preceding failure of the
nal value to define an acceptable range for the property.
facesheet, or the tension side facesheet are not acceptable
3.2.4 parent facesheet, n—the parent facesheet is the
failure modes. Careful post-test inspection of the specimen is
facesheet that is cured during the first cure cycle.
required as facesheet failure occurring in proximity to the
3.2.5 secondary bonded (repair) facesheet, n—the second-
loading points can be caused by local through-thickness
ary bonded facesheet is a pre-cured laminate that is bonded to
compression or shear failure of the core that precedes failure of
the parent pre-cured facesheet using a separate adhesive
the facesheet.
material (sometimes referred to as a pre-cured patch repair).
5. Significance and Use
3.3 Symbols:
5.1 Flexuretestsonflatsandwichpanelconstructionmaybe
c—core thickness
conducted to determine facesheet scarf or step joint compres-
CV—sample coefficient of variation, in percent
sive strength.
d—sandwich total thickness
f
E —effective backskin (tension side) facesheet chord
b 5.2 This practice is limited to obtaining the compressive
modulus
strength of the sandwich panel scarf and step joint facesheets.
f
E —effective repair (compressive side) facesheet chord
Due to the curvature of the flexural test specimen when loaded,
r
modulus
facesheet compression strength from this test may not be
cu
F —ultimate compressive strength, based on repair lami-
equivalent to the facesheet compression strength of sandwich
r
nate thickness
structures subjected to pure edgewise (in-plane) compression.
h —specimen nominal backskin side laminate facesheet
b
5.3 Factors that influence the compressive response and
thickness as specified by the test requestor (nominal ply
should therefore be reported include the following: materials
thickness may be available from the relevant material specifi-
(laminate facesheet, core, and adhesive); methods of material
cation)
fabrication; methods of material preparation, including surface
preparation prior to bonding, lay-up, specimen facesheet stack-
ing sequence, and overall thickness; core geometry (cell size);
Available from SAE International (SAE), 400 Commonwealth Dr.,Warrendale,
PA 15096, http://www.sae.org. core density; adhesive thickness; joint taper ratio or step
D8285/D8285M − 19
FIG. 1 Compressive Sandwich Beam Tapered and Stepped Joint Specimen – Overall Geometry (SI)
FIG. 2 Compressive Sandwich Beam Tapered and Stepped Joint Specimen – Overall Geometry (Inch-Pound)
length; ply overlap length; relative thickness and stiffness of test direction, which may be obtained from this practice,
parent and repair laminates; adhesive bond stiffness; specimen include the following:
preparation; specimen conditioning; environment of testing; 5.3.1 Ultimate compressive strength (based on the nominal
cu
specimenalignment;speedoftesting;timeattemperature;void repair material thickness), (F ).
r
content; and volume percent reinforcement. Properties, in the 5.3.2 Ultimate running load per ply, (N).
j
D8285/D8285M − 19
NOTE 2—Concentrated forces on beams with thin facesheets and low
parent sandwich panel shall be specified by the test requestor
density cores can produce results that are difficult to interpret, especially
and documented in the test report.
close to the failure point.Wider loading blocks and rubber pads may assist
6.3.2 Step Joint Filler Plies—The stepped joint specimen
in distributing the forces.
should have a filler ply to avoid waviness in the repair plies.
NOTE 3—To ensure that simple sandwich beam theory is valid, a good
The filler ply should ideally be the same thickness as the
rule of thumb for the four-point bending test is the support span length
divided by the sandwich thickness should be greater than 20 (S/d > 20)
bottom ply of the parent laminate. The standard test specimen
with the ratio of repair material facesheet thickness to core thickness less
configuration in this practice for unidirectional tape materials
than 0.1 (h /c < 0.1).
r
uses a +45 ply as a filler ply. If an equivalent thickness fabric
ply repair material is available, that could be used for the filler
6. Interferences
ply to provide a balanced lay-up.
6.1 Material and Specimen Preparation—Poormaterialfab-
6.3.3 In baseline final mechanical property calculations, it is
rication practices, lack of control of fiber alignment, and
recommended that the filler ply thickness be omitted, so that
damage induced by improper coupon machining are known
the calculated stress and load/ply values are consistent with the
causes of high material data scatter in composites. For the
number of parent plies and repair plies. If the test requester
bonded joint specimens, the quality of the co-cured laminate
electstousethefillerplythicknessinthecalculations,thenthis
(ply positioning, lengths, impregnation for wet lay-up material
should be clearly documented in the test report.
system), lack of orientation control of the parent laminate or
6.4 Edge Effects in Angle Ply Laminates—Premature failure
pre-cured patch, and quality of the bond between the parent
can occur as a result of edge softening in laminates containing
and pre-cure or co-cured bonded laminates will have signifi-
off-axis plies. Because of this, the strength for angle ply
cant effects on the test results.
laminates can be lower than expected. For multidirectional
6.2 Geometry—Specific geometric factors that affect sand-
laminates containing significant axial fiber, the effect is not as
wich facesheet strength include facesheet thickness, core cell
significant.
geometry, out-of-plane curvature and facesheet surface flatness
6.5 Core Material—If the core material has insufficient
(toolside or bagside surface in compression).
shear or compressive strength, it is possible that the core may
6.3 Specimen Design—The bonded joint test specimen in-
locally crush at or near the loading points, thereby resulting in
volves a parent and a repair laminate. These two laminates
facesheet failure due to local stresses. In other cases, facesheet
typically do not use the same material system. There are a
failure can cause local core crushing. Where there is both
number of variables and factors which influence the selection
facesheet and core failure in the vicinity of one of the loading
of the repair laminate lay-up relative to the parent laminate.
points, it can be difficult to determine the failure sequence in a
Generally the repair lay-up is designed to match or slightly
post-mortem inspection of the specimen as the failed speci-
exceed the stiffness of the parent laminate, and ideally the
mens look very similar for both sequences.
repair material type (fabric or tape) and the ply thicknesses are
6.6 Environment—Resultsareaffectedbytheenvironmental
the same as for the parent material. When they are different,
conditions under which the tests are conducted. Specimens
repair design compromises are necessary to obtain sufficient
tested in various environments can exhibit significant differ-
repairstiffnessandstrengthwhilenotmakingtherepairthicker
ences in both failure force and failure mode. Experience has
than the parent laminate. Details of repair design are beyond
demonstrated that elevated-temperature, humid environments
the scope of this practice. The results from this practice are
can be critical for laminate facesheet compressive strength.
reported as simple stress and force-per-width values; the joint
The critical environmental condition for bonded joint speci-
specimen design will influence the validity of these reported
mens is complicated by having multiple materials in the test
results for use with bonded repair analysis methods.All details
specimen geometry. The failure modes may change between
of the repair design and fabrication process shall be docu-
laminate facesheet compressive modes, bondline modes, and
mented in the test report.
laminate interfacial modes as environmental conditions
6.3.1 In order to support the extended total length of the
change. Critical environments must be assessed independently
joint repair region on the sandwich beam, the overall standard
for each specific combination of material systems (parent
specimen length is 813 mm [32 in.] for this practice. Typical
material, repair material, adhesive (if used), core, and core-to-
joint total repair length is 254 mm [10.0 in.]. See Figs. 1 and 2
facesheet interfacial adhesive used) that is tested.
and Tables 1 and 2 for more definition of specimen geometries.
Alternate non-standard repair designs may allow shorter over- 6.7 Failure Mode—For a valid test, final failure of the
all specimen lengths.The location of the tool or bag side of the specimen must occur within the gauge section. Which failure
TABLE 1 Compressive Tapered Joint Standard Specimen Geometry Requirements
B
Specimen Type Specimen Lay-Up – Parent and Taper Ratio Repair Ply Overlap Specimen Width Total Repair Length
A
Repair Length
Tapered [+45°/0°/90°/-45°]s (Tape) or 50:1 13 ± 2 mm 80±3mm 254 ± 3 mm
[+45°/0°/90°/-45°]sf (Fabric) [0.5 ± 0.08 in.] [3.0 ± 0.1 in.] [10.0±0.10in.]
A
The standard repair ply overlap length is designed for a repair ply material thickness less than or equal to 0.2 mm [0.008 in.]. For repair materials with significantly different
ply thicknesses, the repair ply overlap length should be adjusted accordingly.
B
For the standard specimen, the Total Repair Length shall be approximately 254 mm [10 in.].
D8285/D8285M − 19
TABLE 2 Compressive Stepped Joint Standard Specimen Geometry Requirements
A B
Specimen Type Specimen Lay-Up – Parent and Repair Step/Ply Overlap Length Specimen Width Total Repair Length
Stepped [+45°/0°/90°/-45°]s (Tape) or 13±2mm 80±3mm 254 ± 3 mm
[+45°/0°/90°/-45°]sf (Fabric) [0.5 ± 0.08 in.] [3.0 ± 0.1 in.] [10.0 ± 0.10 in.]
A
For the standard specimen, the repair ply material thickness shall be within +25 % ⁄-10 % of the parent ply material thickness.
B
For the standard specimen, the Total Repair Length shall be approximately 254 mm [10 in.].
modes are deemed acceptable will be governed by the particu- 7.2.1.1 Support and loading bars and pressure pads (if used)
lar material, configuration, and application (see 11.4 and Fig. shall be in conformance of recommended practices defined in
3).
Test Method D7249/D7249M. Pressure pads shall not overlap
the repair plies.
7. Apparatus
7.3 Testing Machine—The testing machine shall be in con-
7.1 Micrometers and Calipers—Micrometers and calipers
formance with Practices E4 and shall satisfy all requirements
usedshallbeinaccordancewithTestMethodD7249/D7249M.
defined in Test Method D7249/D7249M.
7.2 General Apparatus—General apparatus shall be in ac-
7.4 Conditioning Chamber—When conditioning materials
cordance with Test Method D7249/D7249M.
in other than ambient laboratory environments, a temperature/
7.2.1 Standard 4-Point Loading Configuration—The stan-
moisture-level controlled environmental conditioning chamber
dard loading fixture shall consist of a 4-point loading configu-
is required that shall be capable of maintaining the required
ration with two support bars that span the specimen width
relative temperature to within 63°C[65 °F] and the required
located below the specimen and two loading bars that span the
relative vapor level to within 63 %. Chamber conditions shall
specimen width located on the top of the specimen in accor-
be monitored either on an automated continuous basis or on a
dance with Test Method D7249/D7249M. Support and loading
manual basis at regular intervals.
barsandpressurepadsshallbeinaccordancewithTestMethod
D7249/D7249M. The standard support span (S) for this prac- 7.5 Environmental Chamber—Achambercapableofenclos-
tice will be 762 mm [30.0 in.], and the standard load s
...