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GB/T 40388-2021 English PDF (GBT40388-2021)

GB/T 40388-2021 English PDF (GBT40388-2021)

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GB/T 40388-2021: Test method for shear strength of C/C composites

This document specifies the method principle, test equipment, test pieces, test conditions, test procedures, calculations and test report of the test method for shear strength of C/C composites at room temperature. This document applies to the determination of the shear strength of C/C composites by the method of punching and shearing.
GB/T 40388-2021
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 83.120
CCS Q 23
Test method for shear strength of C/C composites
ISSUED ON: AUGUST 20, 2021
IMPLEMENTED ON: MARCH 01, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of the PEOPLE Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 4
4 Method principle ... 5
5 Test equipment ... 5
6 Test pieces ... 5
7 Test conditions ... 7
8 Test procedures ... 7
9 Calculation ... 8
10 Test report ... 9
Appendix A (Informative) Diagram of shearing fixture and main components ... 10 Test method for shear strength of C/C composites
1 Scope
This document specifies the method principle, test equipment, test pieces, test conditions, test procedures, calculations and test report of the test method for shear strength of C/C composites at room temperature.
This document applies to the determination of the shear strength of C/C composites by the method of punching and shearing.
2 Normative references
The following documents 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 are applicable to this document.
3.1 C/C composites
Carbon fiber-reinforced carbon matrix composites.
[Source: GB/T 33501-2017, 3.1]
3.2 The XY direction
Direction of no weft or continuous long fiber tiling planes in C/C composites (3.1). [Source: GB/T 33501-2017, 3.6]
3.3 The Z direction
Direction vertical to the XY direction (3.2) in the C/C composites (3.1). [Source: GB/T 33501-2017, 3.7]
Valid samples in each group shall be no less than 5.
7 Test conditions
7.1 Test environment
The test environment shall meet the laboratory standard environment specified in GB/T 1446.
7.2 Sample state adjustment
Before the test, the sample shall be placed at least 24 h under the condition of laboratory standard environment.
8 Test procedures
8.1 Check the appearance of the sample according to the provisions of GB/T 1446; check the number and direction of each sample.
8.2 Adjust the state of the sample according to the provisions of 7.2.
8.3 After the sample state adjustment, measure the sample thickness h at four positions in the direction of 90?? to each other, at the diameter of 25 mm of the sample, accurate to 0.01 mm; take the arithmetic mean of the four measurement results. Measure the diameter d at any two positions of the inner ring clamping block on the fixture, accurate to 0.02 mm; take the arithmetic mean of the two measurement results. The schematic diagram of the shearing fixture assembly is shown in Figure 3.
8.4 Fix the pin shaft on the force acting platform; respectively insert the upper inner ring clamping block, upper outer ring, sample and lower inner ring clamping block into the pin shaft in sequence; use the gasket and the sample clamping nut to fasten the sample in the upper and lower inner ring clamping blocks. The tightening torque is 1 N??m [see Figure 3a)].
8.5 Put the combination of the upper and lower inner ring clamping blocks of the sample into the lower outer ring of the test fixture, where the upper outer ring is connected to the lower outer ring through the clamp screw [see Figure 3b)], and the tightening torque of the screw is 1 N??m. The sample installation is then completed [see Figure 3c)].
8.6 Center the test fixture on the compression platform of the testing machine; continuously apply a compressive load to the sample at a loading rate of 2 mm/min until the sample fails or the load drops to 30% of the maximum load; continuously measure the load-displacement data; record the maximum load.
Pmax ?€? maximum load before failure, in Newtons (N);
d ?€? diameter of the upper inner ring clamping block of the fixture, in millimeters (mm);
h ?€? sample thickness, in millimeters (mm).
9.2 Calculate the arithmetic mean, standard deviation and dispersion coefficient according to GB/T 1446.
10 Test report
The test report generally includes the following contents:
a) name of the test item and number of this document;
b) test time, place and test environmental conditions;
c) sample source, material variety and specification;
d) sample number, size, sample direction and quantity;
e) types and specifications of test equipment and instruments;
f) loading rate;
g) load-displacement curve for each sample;
h) the measured value of each sample, the mean, standard deviation and
dispersion coefficient of each group of samples;
i) test personnel, date and others.

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