THERMAL CYCLING OF PHENYLETHYNYL-TERMINATED PMDA TYPE ASYMMETRIC POLYIMIDE COMPOSITES

摘要

The effects of thermal cycling on a polymerized monomeric reactant (PMR) type polyimide reinforced with carbon fibers were investigated. The PMR matrix resin (TriA X) is derived from the reaction of pyromellitic dianhydride (PMDA), 2-pheny-4,4’-diaminodipheny ether (p-ODA) and 4-phenylethynylphthalic anhydride (PEPA), and exhibits high toughness and an amorphous structure due to an asymmetric and non-planar backbone. Composite samples were subjected to 2000 thermal cycles between -54℃ and 232℃. At 400-cycle intervals, laminates were inspected for microcracks and short-beam shear (SBS) tests were performed. After 2000 thermal cycles, no microcracks/cracks were observed, and the SBS strength at 23℃ and 232℃ decreased 3-9 % and 3-4 %, respectively. The slight reduction in SBS strength of composites after thermal cycling was attributed to minor effects of thermal cycling and the absence of microcracks/cracks. The polyimide composites exhibited resistance to microcracking during thermal cycling and >90% retention of SBS strength.