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GB/T 40398.2-2021 PDF in English

GB/T 40398.2-2021 (GB/T40398.2-2021, GBT 40398.2-2021, GBT40398.2-2021)
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GB/T 40398.2-2021: PDF in English (GBT 40398.2-2021)

GB/T 40398.2-2021
ICS 29.050
CCS Q 50
Test method for C-C composites - Part 2.Flexural properties
Issued by. State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword... 3 
Introduction... 4 
1 Scope... 5 
2 Normative references... 5 
3 Terms and definitions... 5 
4 Principle... 7 
5 Equipment... 7 
6 Samples... 8 
7 Test conditions... 9 
8 Test procedures... 9 
9 Calculation... 10 
10 Test report... 12 
Appendix A (Informative) Failure mode of the flexural test for C-C composites... 13 
Test method for C-C composites - Part 2.Flexural properties
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.
C-C composites
Carbon fibre-reinforced carbon matrix composites.
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.
Punctured three-dimensional C-C composites
C-C composites prepared with the punctured three-dimensional carbon fibre textile as
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
Needled quasi-three-dimensional C-C composites
C-C composites prepared with needled quasi-three-dimensional carbon fibre textile as
The XY direction
The direction of the flat surface of non-weft cloth or continuous long fibre in the C-C
The Z direction
The direction perpendicular to the XY direction in the C-C composites
Flexural strength
The maximum stress experienced by a material when it fails or reaches a specified
deflection under a flexural load.
Flexural modulus
The ratio of the flexural stress to the corresponding flexural strain in the elastic range
of a material.
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.
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.