Mechanical behavior of a woven graphite/PMR-15 composite at room and elevated temperatures determined from the ±45° tensile, and Iosipescu shear tests

Failure and stiffness properties of a woven 8 harness satin (8HS) graphite/PMR-15 composite have been investigated at room temperature and at 315°C by performing the ±45° tensile and Iosipescu tests. Acoustic emission has been monitored during testing. The critical loads for the initiation of damage in the composite have been determined. In particular, the specimen width effect has been investigated in the case of the ±45° specimens by testing the specimens with their width ranging from 12.7-50.8 mm. The results from the high temperature tests have been compared with the room temperature data presented in Refs. 1 and 2. Similar to the room temperature ±45° tests, the shear stresses at the onset of intralaminar damage in the specimens and the shear stresses at the maximum loads at 315°C are significantly affected by the specimen width effect. The trends in the damage initiation stresses and the maximum stresses as a function of specimen width at 315°C have been found to be very similar to the room temperature data with the stresses increasing almost linearly with the specimen width. It has also been shown in this project that the shear stresses at the onset of intralaminar damage and at the maximum load at 315°C depend very strongly on the specimen type. The shear stresses determined at the onset of damage and maximum loads from the Iosipescu tests at 315°C are noticeably higher than the stresses from the ±45° tests. The ±45° tensile test significantly underestimates the room and elevated temperature shear strength properties of the 8HS graphite/PMR-15 composite in comparison with the Iosipescu shear test.