BS ISO 22459-2020 Fine ceramics [advanced ceramics, advanced technical ceramics) – Reinforcement of ceramic composites一Determination of distribution of tensile strength and tensile strain to fail lure of filaments within a multifilament tow at ambient temperature.
9.4 Selection of strain rate
A strain rate around 10-4s-1 shall he used for all the tests. The corresponding crosshead displacement rate shall be determined from a test on a specimen with the largest gauge length of 300 mm performed according to 9,5. The force-displacement curve obtained from this test shall have the appearance shown in Figure 7. In particular, the curve shall have a linear followed by a nonlinear rising part, as well as a nonlinear decreasing part. It shall furthermore meet the validity requirements of 91. When the force- displacement curve does not meet these criteria, tests at lower crosshead displacement rates shall be performed until this is the case. Calculate the strain rate from the displacement rate and check whether it falls in the required range. linot, decrease the crosshead displacement rate until this is the case. Use this crosshead rate in all subsequent tests, irrespective of the gauge length of the specimen.
9.5 Test procedure
Mount the specimen in the load train. Set the displacement rate on the machine. When a window type specimen is used, carefully cut both sides of the supporting plates. Start the load versus displacement recording. Load the specimen up to failure under constant displacement rate. Remove the failed specimen from the grips. Check the validity requirements of 91.
It is recommended that a lubricant is introduced in the tow in order to reduce inter-filament friction. Lubricant oil and petrol have been used on SIC fibres.
9.6 Determination of load train compliance
Repeat steps 92. 93 and 9.5 three times for each of the gauge lengths of 100 mm, 200 mm and 300 mm.
9.7 Test validity
The test is invalid in the following circumstances:
— failure to specify and record test conditions;
— the linear region in the rising part of the force-displacement curve is lacking;
— one or more load drops with an amplitude larger than 5 % of the maximum force occur in the rising
part of the force-displacement curve;
— filament rupture occurs preferentially in the grips or near the gripped ends (the test is valid when both parts of the test specimen after failure have a significant number of filaments, but not all, extending beyond half of the gauge length);
— one or more load drops at constant strain with an amplitude larger than 5 % of the maximum force occur beyond the point of maximum force of the force-displacement curve (this restriction does not apply for the determination of the load train compliance);
— the nonlinear domain at the origin of the curve exceeds 10 % of the displacement corresponding to the maximum force.
10 Calculation of results
10.1 Calculation of the load train compliance C1
Calculate the initial total compliance C,o (mm/N) for the tests at each of the gauge lengths from the slope 1/C1,0 of the linear rising part of the force (N)-displacement (mm) curve (see Figure 7). Calculate the average value C0 at each of the three gauge lengths.
Plot C0 against Lo (see Figure 8).BS ISO 22459 pdf download.