Comparative Testing to Assess the Equivalence of CEN and ASTM Test Methods for Composite Materials

摘要

An initial assessment of equivalence between CEN and ASTM test methods was performed and documented in DOT/FAA/AR-04/24. That study recommended additional test data to assess test method equivalency for four types of tests. The results of the four types of tests are contained in this report. First, lamina compression testing was performed to investigate the effects of different specimen gage lengths between either the prEN 2850-B and SACMA SRM 1 test methods (5 and 4.75 mm, respectively) and the AMS 2980 and 3970 specifications (12.5 mm). The results suggest that the gage length difference investigated (4.75 mm versus 12.5 mm) can produce significant differences in the apparent lamina compression strength. However, this difference is believed to be due to specimen buckling that occurred for specimens with longer gage lengths, which is an unacceptable failure mode. Second, laminate compression tests were performed to investigate the method used to load the test fixture. The results suggest that the end-loaded test fixture shown in the SACMA SRM 3-94 test method is not suitable without additional clamping force applied near the specimen ends to prevent end-brooming failures. However, it is expected that through the modification of the existing test fixture to include more clamping bolts, an end-loaded test procedure can be produced that is capable of producing equivalent test results to the shear-loaded ASTM D 6484 test method. Third, in-plane shear testing was performed using plus or minus 45 deg type composite laminates loaded in tension to investigate laminate thickness effects. Test results showed that the 0.2% offset shear strength, the 5% shear strength measures, and the shear moduli calculated following the prEN 6031/AMS and ASTM D 3518 test methods are in good agreement and independent of laminate thickness over the thickness ranges specified in the two test methods. Thus, these two shear test methods are believed to produce equivalent results when testing either tape or fabric laminates. Finally, constituent content was determined to compare procedures EN 2564 Method A and ASTM D 3171 Method I procedure B. The results showed that EN 2564 Method A and ASTM D 3171 Method I procedure B produced similar values for both the fiber volume percent and the matrix volume percent. However, the increased accuracy of the ASTM D 3171 test method due to the larger specimen size and the greater weighing accuracy produced more realistic values of void volume fraction than the EN 2564 Method A test method.