GB/T 40388-2021Test method for shear strength of C/C composites (English PDF)

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.

6 Test pieces

Valid samples in each group shall be no less than 5.

7 Test conditions

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.

9 Calculation

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. […]