ASTM C1869-18(2023)
(Test Method)Standard Test Method for Open-Hole Tensile Strength of Fiber-Reinforced Advanced Ceramic Composites
Standard Test Method for Open-Hole Tensile Strength of Fiber-Reinforced Advanced Ceramic Composites
SIGNIFICANCE AND USE
5.1 Open-hole tests of composites are used for material and design development for the engineering application of composite materials (5-11). The presence of an open hole in a composite component reduces the cross-sectional area available to carry an applied force, creates stress concentrations, and creates new edges where delamination may occur. Standardized open-hole tests for composite materials can provide useful information about how a composite material may perform in an open-hole application and how to design the composite for notches and holes.
5.2 The test method defines two baseline test specimen geometries and a test procedure for producing comparable, reproducible OHT test data. The test method is designed to produce OHT strength data for structural design allowables, material specifications, material development and comparison, material characterization, and quality assurance. The mechanical properties that may be calculated from this test method include:
5.2.1 The open-hole (notched) tensile strength (SOHTx) for test specimen with a hole diameter x (mm).
5.2.2 The net section tensile strength (SNSx) for a test specimen with a hole diameter x (mm).
5.2.3 The proportional limit stress (σ0) for an OHT specimen with a given hole diameter.
5.2.4 The stress response of the OHT test specimen, as shown by the stress-time or stress-displacement plot.
5.3 Open-hole tensile tests provide information on the strength and deformation of materials with defined through-holes under uniaxial tensile stresses. Material factors that influence the OHT composite strength include the following: material composition, methods of composite fabrication, reinforcement architecture (including reinforcement volume, tow filament count and end-count, architecture structure, and laminate stacking sequence), and porosity content. Test specimen factors of influence are: specimen geometry (including hole diameter, width-to-diameter ratio, and diameter-to-thickness rati...
SCOPE
1.1 This test method determines the open-hole (notched) tensile strength of continuous fiber-reinforced ceramic matrix composite (CMC) test specimens with a single through-hole of defined diameter (either 6 mm or 3 mm). The open-hole tensile (OHT) test method determines the effect of the single through-hole on the tensile strength and stress response of continuous fiber-reinforced CMCs at ambient temperature. The OHT strength can be compared to the tensile strength of an unnotched test specimen to determine the effect of the defined open hole on the tensile strength and the notch sensitivity of the CMC material. If a material is notch sensitive, then the OHT strength of a material varies with the size of the through-hole. Commonly, larger holes introduce larger stress concentrations and reduce the OHT strength.
1.2 This test method defines two baseline OHT test specimen geometries and a test procedure, based on Test Methods C1275 and D5766/D5766M. A flat, straight-sided ceramic composite test specimen with a defined laminate fiber architecture contains a single through-hole (either 6 mm or 3 mm in diameter), centered by length and width in the defined gage section (Fig. 1). A uniaxial, monotonic tensile test is performed along the defined test reinforcement axis at ambient temperature, measuring the applied force versus time/displacement in accordance with Test Method C1275. Measurement of the gage length extension/strain is optional, using extensometer/displacement transducers. Bonded strain gages are optional for measuring localized strains and assessing bending strains in the gage section.
FIG. 1 OHT Test Specimens A and B
1.3 The open-hole tensile strength (SOHTx) for the defined hole diameter x (mm) is the calculated ultimate tensile strength based on the maximum applied force and the gross cross-sectional area, disregarding the presence of the hole, per common aerospace practice (see 4.4). The net section ...
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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: C1869 − 18 (Reapproved 2023)
Standard Test Method for
Open-Hole Tensile Strength of Fiber-Reinforced Advanced
Ceramic Composites
This standard is issued under the fixed designation C1869; 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 strength (S ) is also calculated as a second strength property,
NSx
accounting for the effect of the hole on the cross-sectional area
1.1 This test method determines the open-hole (notched)
of the test specimen.
tensile strength of continuous fiber-reinforced ceramic matrix
1.4 This test method applies primarily to ceramic matrix
composite (CMC) test specimens with a single through-hole of
defined diameter (either 6 mm or 3 mm). The open-hole tensile composites with continuous fiber reinforcement in multiple
directions. The CMC material is typically a fiber-reinforced,
(OHT) test method determines the effect of the single through-
hole on the tensile strength and stress response of continuous 2-D, laminated composite in which the laminate is balanced
and symmetric with respect to the test direction. Composites
fiber-reinforced CMCs at ambient temperature. The OHT
with other types of reinforcement (1-D, 3-D, braided, unbal-
strength can be compared to the tensile strength of an un-
anced) may be tested with this method, with consideration of
notched test specimen to determine the effect of the defined
how the different architectures may affect the notch effect of
open hole on the tensile strength and the notch sensitivity of the
the hole on the OHT strength and the tensile stress-strain
CMC material. If a material is notch sensitive, then the OHT
response. This test method does not directly address discon-
strength of a material varies with the size of the through-hole.
tinuous fiber-reinforced, whisker-reinforced, or particulate-
Commonly, larger holes introduce larger stress concentrations
reinforced ceramics, although the test methods detailed here
and reduce the OHT strength.
may be equally applicable to these composites.
1.2 This test method defines two baseline OHT test speci-
1.5 This test method may be used for a wide range of CMC
men geometries and a test procedure, based on Test Methods
materials with different reinforcement fibers and ceramic
C1275 and D5766/D5766M. A flat, straight-sided ceramic
matrices (oxide-oxide composites, silicon carbide (SiC) fibers
composite test specimen with a defined laminate fiber archi-
in SiC matrices, carbon fibers in SiC matrices, and carbon-
tecture contains a single through-hole (either 6 mm or 3 mm in
carbon composites) and CMCs with different reinforcement
diameter), centered by length and width in the defined gage
architectures. It is also applicable to CMCs with a wide range
section (Fig. 1). A uniaxial, monotonic tensile test is performed
of porosities and densities.
along the defined test reinforcement axis at ambient
temperature, measuring the applied force versus time/
1.6 Annex A1 and Appendix X1 address how test specimens
displacement in accordance with Test Method C1275. Mea-
with different geometries and hole diameters may be prepared
surement of the gage length extension/strain is optional, using
and tested to determine how those changes will modify the
extensometer/displacement transducers. Bonded strain gages
OHT strength properties, determine the notch sensitivity, and
are optional for measuring localized strains and assessing
affect the stress-strain response.
bending strains in the gage section.
1.7 The test method may be adapted for elevated tempera-
1.3 The open-hole tensile strength (S ) for the defined
OHTx
ture OHT testing by modifying the test equipment, specimens,
hole diameter x (mm) is the calculated ultimate tensile strength
and procedures per Test Method C1359 and as described in
based on the maximum applied force and the gross cross-
Appendix X2. The test method may also be adapted for
sectional area, disregarding the presence of the hole, per
environmental testing (controlled atmosphere/humidity at
common aerospace practice (see 4.4). The net section tensile
moderate (<300 °C) temperatures) of the OHT properties by
the use of an environmental test chamber, per 7.6.
1.8 Values expressed in this test method are in accordance
This test method is under the jurisdiction of ASTM Committee C28 on
with the International System of Units (SI) and IEEE/ASTM SI
Advanced Ceramics and is the direct responsibility of Subcommittee C28.07 on
10.
Ceramic Matrix Composites.
Current edition approved May 1, 2023. Published June 2023. Originally
1.9 This standard does not purport to address all of the
approved in 2018. Last previous edition approved in 2018 as C1869 – 18. DOI:
10.1520/C1869-18R23. safety concerns, if any, associated with its use. It is the
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1869 − 18 (2023)
C1239 Practice for Reporting Uniaxial Strength Data and
Estimating Weibull Distribution Parameters for Advanced
Ceramics
C1275 Test Method for Monotonic Tensile Behavior of
Continuous Fiber-Reinforced Advanced Ceramics with
Solid Rectangular Cross-Section Test Specimens at Am-
bient Temperature
C1326 Test Method for Knoop Indentation Hardness of
Advanced Ceramics
C1327 Test Method for Vickers Indentation Hardness of
Advanced Ceramics
C1359 Test Method for Monotonic Tensile Strength Testing
of Continuous Fiber-Reinforced Advanced Ceramics With
Solid Rectangular Cross Section Test Specimens at El-
evated Temperatures
C1465 Test Method for Determination of Slow Crack
Growth Parameters of Advanced Ceramics by Constant
Stress-Rate Flexural Testing at Elevated Temperatures
C1773 Test Method for Monotonic Axial Tensile Behavior
of Continuous Fiber-Reinforced Advanced Ceramic Tubu-
lar Test Specimens at Ambient Temperature
C1793 Guide for Development of Specifications for Fiber
Reinforced Silicon Carbide-Silicon Carbide Composite
Structures for Nuclear Applications
D3039/D3039M Test Method for Tensile Properties of Poly-
mer Matrix Composite Materials
D3878 Terminology for Composite Materials
D5766/D5766M Test Method for Open-Hole Tensile
Strength of Polymer Matrix Composite Laminates
D6856/D6856M Guide for Testing Fabric-Reinforced “Tex-
tile” Composite Materials
E4 Practices for Force Calibration and Verification of Test-
FIG. 1 OHT Test Specimens A and B
ing Machines
E6 Terminology Relating to Methods of Mechanical Testing
E83 Practice for Verification and Classification of Exten-
someter Systems
responsibility of the user of this standard to establish appro-
E105 Guide for Probability Sampling of Materials
priate safety, health, and environmental practices and deter-
E122 Practice for Calculating Sample Size to Estimate, With
mine the applicability of regulatory limitations prior to use.
Specified Precision, the Average for a Characteristic of a
1.10 This international standard was developed in accor-
Lot or Process
dance with internationally recognized principles on standard-
E251 Test Methods for Performance Characteristics of Me-
ization established in the Decision on Principles for the
tallic Bonded Resistance Strain Gages
Development of International Standards, Guides and Recom-
E337 Test Method for Measuring Humidity with a Psy-
mendations issued by the World Trade Organization Technical
chrometer (the Measurement of Wet- and Dry-Bulb Tem-
Barriers to Trade (TBT) Committee.
peratures)
2. Referenced Documents E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
2.1 ASTM Standards:
E1012 Practice for Verification of Testing Frame and Speci-
C373 Test Methods for Determination of Water Absorption
men Alignment Under Tensile and Compressive Axial
and Associated Properties by Vacuum Method for Pressed
Force Application
Ceramic Tiles and Glass Tiles and Boil Method for
E1402 Guide for Sampling Design
Extruded Ceramic Tiles and Non-tile Fired Ceramic
E2208 Guide for Evaluating Non-Contacting Optical Strain
Whiteware Products
Measurement Systems
C1145 Terminology of Advanced Ceramics
IEEE/ASTM SI 10 American National Standard for Metric
Practice
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 3. Terminology
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
3.1 Definitions—Annex A2 lists pertinent general defini-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. tions from Practice E1012, Terminology C1145 (advanced
C1869 − 18 (2023)
ceramics), Terminology D3878 (composite materials), and 3.2.7 principal structural axis, n—in a composite flat plate
Terminology E6 (tensile testing), with the appropriate source or rectangular bar, the composite coordinate axis/direction
given in bold font. with the maximum in-plane Young’s modulus (based on
Terminology D3878). This is commonly the axis with the
3.2 Definitions of Terms Specific to This Standard:
highest fiber fraction or the warp direction of the weave.
3.2.1 If the term represents a physical quantity, its analytical
3.2.8 test reinforcement axis alignment, n—the orientation/
dimensions are stated immediately following the term (or letter
alignment of the long tensile test axis of the test specimen with
symbol) in fundamental dimension form, using the following
respect to the principal structural axis.
ASTM standard symbology for fundamental dimensions,
3.2.8.1 Discussion—In composite testing, it is common
shown within square brackets: [M] for mass, [L] for length, [T]
practice to test specimens with different test axis alignments
for time, [θ] for thermodynamic temperature, and [nd] for
(0°, 90°, 645° to the principal structural axis) to determine the
nondimensional quantities. Use of these symbols is restricted
mechanical properties in the different anisotropic directions.
to analytical dimensions when used with square brackets, as
(See Fig. 2.)
the terms may have other definitions when used without the
brackets.
3.2.9 width-to-diameter ratio (w/D), [L/L]—in an open-hole
3.2.2 diameter-to-thickness ratio (D/h), [L/L], n—in an
tensile specimen, the ratio of the specimen width (w) to the
open-hole tensile specimen, the ratio of the hole diameter (D)
hole diameter (D).
to the specimen thickness (h).
3.2.9.1 Discussion—The width-to-diameter ratio may be
3.2.2.1 Discussion—The diameter-to-thickness ratio may be either a nominal value determined from nominal dimensions or
either a nominal value determined from nominal dimensions or
an actual value determined from measured dimensions.
an actual value determined from measured dimensions.
3.3 Symbols:
3.2.3 failure strength, n—the strength parameter (stress,
3.3.1 A—gross cross-sectional area of the test specimen,
torque, moment, force, etc.) that produces material failure in a
disregarding the presence of the through-hole (mm )
given test specimen in a given stress state and test orientation.
3.3.2 A —net cross-sectional area of the test specimen,
NS
3.2.3.1 Discussion—In mechanical testing of ceramic
considering the presence of the through-hole (mm )
composites, failure is often defined by a total or partial loss of
3.3.3 CV—coefficient of variation statistic of a sample
load carrying capacity, marked by the breaking or tearing apart
population for a given property (in percent)
of or damage to the test specimen (synonym—rupture). Failure
3.3.4 D—diameter of the through-hole (mm)
strength is typically defined for a given stress state (tensile,
compression, shear, flexure, torsion) and a given test orienta-
3.3.5 h—test specimen thickness (mm)
tion in the test specimen.
3.3.6 L—total length of the test specimen (mm)
3.2.4 material failure, n—in mechanical testing, the loss of
3.3.7 L —the nominal gage section length of the test
gage
or inability to meet the required load carrying capacity speci-
specimen (mm)
fied in the applicable material or performance requirement,
3.3.8 L —grip section length of the test specimen (mm)
grip
depending on the purpose of the test.
3.3.9 n—number of valid specimen data points for statistical
–2
3.2.5 net section tensile strength (S ), [FL ], n—in the
NSx
calculations
open-hole tensile test, the hole-diameter-adjusted maximum
3.3.10 N —total number of test specimens that were tested
tensile stress which the OHT test specimen (with a through- T
hole of defined diameter x (mm)) is capable of sustaining. The 3.3.11 N —number of valid test specimens
V
net section tensile strength is calculated from the maximum
3.3.12 P —maximum force carried by test specimen prior
max
force during the OHT test carried to failure/rupture and the
to failure (N)
reduced cross-sectional area of the specimen, considering the
presence of the hole.
–2
3.2.6 open-hole (notched) tensile strength (S ), [FL ],
OHTx
n—in the open-hole tensile test, the maximum tensile stress
that the OHT test specimen (with a through-hole of defined
diameter x (mm)) is capable of sustaining. The OHT strength is
calculated from the maximum force during the OHT test
carried to failure/rupture and the original/gross cross-sectional
area of the specimen, disregarding the presence of the hole.
3.2.6.1 Discussion—While the hole causes a stress concen-
tration and reduced net section, it is common aerospace
practice (per Test Method D5766/D5766M) to develop
notched-design allowable strengths, based on gross section
stress, to account for various stress concentrations (fastener
holes, free edges, flaws, damage, and so forth) not explicitly
modeled in the stress analysis. This gross section stress is also
called the “remote stress.” FIG. 2 Test Specimen Alignment
C1869 − 18 (2023)
3.3.13 s.d.—standard deviation statistic of a sample popula- produce higher stress concentrations and reduce the tensile
tion for a given property strength of the CMC. For this reason, the open-hole tensile
(OHT) strength should be qualified by a hole size designator x
3.3.14 S —net section tensile strength in the test direction
NSx
(in mm), so that the test strength (S ) clearly shows what
OHTx
for a test specimen with a through-hole diameter of x mm
size hole was tested. (This is similar to how microhardness
(MPa)
numbers are identified per the type of indenter—HK = hard-
3.3.15 S —ultimate open-hole (notched) tensile strength
OHTx
...
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