ISO 22459:2020 pdf download Fine ceramics (advanced ceramics, advanced technical ceramics) — Reinforcement of ceramic composites — Determination of distribution of tensile strength and tensile strain to failure of filaments within a multifilament tow at ambient temperature
8.4 Number of test specimens For the establishment of the distribution of filament strength and filament rupture strain, three valid tests, as specified in 9.7, of specimens with a 200 mm gauge length are needed. When the elongation of the tow is not measured directly, an additional three valid tests at the other two gauge lengths of 100 mm and 300 mm, as specified in 9.7, are required for the establishment of the load train compliance.
9 Test procedure 9
.1 Determination of the initial cross-section area For the purpose of determining the filament strength distribution, as well as the elastic modulus on the specimens with a 200 mm gauge length, the initial cross-section area of the multifilament tow shall be calculated from the linear density determined according to EN 1007-2, and from the density determined in ISO 10119. Alternatively, the initial cross-section area can be determined by measuring the number and the average diameter of the filaments in the tow, for instance through image analysis.
9.2 Determination of the gauge length The gauge length shall be measured with an accuracy of ± 0,5 mm. 9.3 Gripping The specimen shall be placed in the test equipment in such a way that axial alignment is as accurate as possible. During gripping, care shall be taken not to load the specimen in tension. When the displacement is not measured directly on the tow, the specimen shall be inserted in the grips in such a way that the distance between the grips is equal to or less than the gauge length (see Figure 6).
9.4 Selection of strain rate A strain rate around 10 −4 s −1 shall be 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 9.7. 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. If not, 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 9.7. 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 9.2, 9.3 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.ISO 22459-2020