GB/T 40398.2-2021Test method for C-C composites—Part 2: Flexural properties (English PDF)
炭-炭复合炭素材料试验方法 第2部分：弯曲性能试验
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Issued by
SAMR; SAC
Level / Type
National · Recommended
Issue date
August 20, 2021
Implementation date
March 1, 2022
Scope
GB/T 40398.2-2021 is the English-translated version of 炭-炭复合炭素材料试验方法 第2部分：弯曲性能试验.
GB/T 40398.2-2021 is the part of the C-C composites test series that measures flexural strength and flexural modulus at room temperature. It applies to punctured three-dimensional and needled quasi-three-dimensional carbon fibre-reinforced carbon matrix composites, and can serve as a reference for C-C composites of similar structure.
It defines these materials and their XY and Z directions, and covers the principle, equipment, samples, test conditions, procedure, calculation and test report.
Samples are conditioned for at least 24 h, measured at three sections and loaded at 1 mm/min to 2 mm/min on a 50 mm span until they fail or the load drops by 10%, and the failure mode is recorded, with Appendix A describing the modes. It was issued on 20 August 2021 and has applied since 1 March 2022.
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Document preview — GB/T 40398.2-2021
National Standard of the People's Republic of China
- ICS
- 29.050
- Classification
- Q 50
Issued by: State Administration for Market Regulation; Standardization Administration of the PRC
Contents
- Foreword3
- Introduction4
- 1 Scope5
- 2 Normative references5
- 3 Terms and definitions5
- 4 Principle7
- 5 Equipment7
- 6 Samples8
- 7 Test conditions9
- 8 Test procedures9
- 9 Calculation10
- 10 Test report12
- Appendix A (Informative) Failure mode of the flexural test for C-C composites13
1 Scope
This document specifies the principle, equipment, samples, test conditions, test procedures, calculation and test report of the test method for the flexural properties of C-C composites at room temperature.
This document applies to the determination of flexural strength and flexural modulus of punctured three-dimensional C-C composites and needled quasi-three-dimensional C-C composites at room temperature. It also applies, as a reference, to C-C composites of similar structure.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the version corresponding to that date is applicable to this document; for undated references, the latest version (including all amendments) is applicable to this document.
GB/T 1446, Fiber-reinforced plastics composites - The generals
GB/T 33501-2017, Test method for tensile property of C/C composites
3 Terms and definitions
Terms and definitions determined by GB/T 33501-2017, and the following ones are applicable to this document.
3.1 C-C composites
Carbon fibre-reinforced carbon matrix composites.
3.2 Punctured three-dimensional carbon fibre textile
A three-dimensional integral fabric, of which the XY direction is a continuous long carbon fibre layer, and the Z direction is made of continuous long carbon fibre bundles running in two directions.
3.3 Punctured three-dimensional C-C composites
C-C composites prepared with the punctured three-dimensional carbon fibre textile as reinforcements.
3.4 Needled quasi-three-dimensional carbon fibre textile
Quasi-three-dimensional integral fibre textile, of which the XY direction is carbon fibre non-weft cloth or carbon fibre warp knitted with weft cloth and short carbon fibre mesh layer, and the Z direction is made by introducing short carbon fibre by needle punching process.
3.5 Needled quasi-three-dimensional C-C composites
C-C composites prepared with needled quasi-three-dimensional carbon fibre textile as reinforcements.
3.6 The XY direction
The direction of the flat surface of non-weft cloth or continuous long fibre in the C-C composites.
3.7 The Z direction
The direction perpendicular to the XY direction in the C-C composites
3.8 Flexural strength
The maximum stress experienced by a material when it fails or reaches a specified deflection under a flexural load.
3.9 Flexural modulus
The ratio of the flexural stress to the corresponding flexural strain in the elastic range of a material.
8 Test procedures
8.1.1 Check the appearance of the samples according to the provisions in GB/T 1446, and number each sample.
8.1.2 Before the test, place the sample under the laboratory standard environmental conditions for conditioning for at least 24 h.
8.1.3 After the sample conditioning, measure the width and thickness at the left, middle and right sections of the working section of the sample, and take the arithmetic mean of the three measurements. The measurement accuracy is not less than 0.02 mm.
8.1.4 Draw a vertical line at the center of the length direction of the test piece, and draw two symmetrical span lines with the vertical line as the center.
8.1.5 Adjust the span of the support on the beam of the base of the test fixture to 50 mm, with an accuracy of ±0.1 mm; then, place the beam of the fixture on the compression platform of the testing machine, where the upper indenter is centered and clamped to the chuck of the testing machine, and the indenter is parallel to the axis of the support.
8.1.6 Place the sample on the fixture support, where the center line on the sample is aligned with the center line of the indenter, and the two span lines are aligned with the center line of the support.
8.1.7 Install a deflectometer or an extensometer in the middle of the two supports of the beam of the fixture base, where the head of the deflectometer or the extensometer adapter is in contact with the lower surface of the sample.
8.2 Testing
8.2.1 Set the load zero, and set the deflectometer or extensometer displacement zero.
8.2.2 Continuously apply a flexural load to the sample at the set loading rate of 1 mm/min ~ 2 mm/min until the sample fails or the load drops by 10%; continuously measure the load-displacement data; record the maximum load at the time of failure and the failure mode.
8.2.3 Visually inspect the failure part of the sample; record the failure mode of the sample and take pictures.
Note: Appendix A provides the failure mode of the flexural test for C-C composites.
9 Calculation
9.1 Flexural strength
Calculate the flexural strength according to Formula (1), and retain 3 significant figures for the result. […]
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This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 15 pages — is available in the English PDF.
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