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The delamination behavior is investigated in static and cyclic creep at elevated temperatures (443K to 483K) using double cantilever beam (DCB) specimens of unidirectional carbon fiber reinforced plastics (CFRP), APC-2 (carbon fiber: AS4 and matrix: poly-ether-ether-ketone (PEEK)). The delamination crack steadily propagates under Mode I loading conditions along the boundaries between matrix and fibers. Wedge-shaped and white-colored zones, where matrix creep is predominant, are observed near the crack tip in static as well as cyclic creep. The crack opening displacement (COD) rate experimentally observed coincides with the elastic COD rate calculated from the change in elastic compliance due to the crack propagation. It implies that the elastic stress field governs the specimen except for the small creep zone. In other words, the creep crack propagates under small scale creep (SSC) where the creep deformation is constrained by fibers and confined in the vicinity of the crack tip. The constraint by fibers characterizes the delamination of composite at elevated temperature as the creep zone usually has swift expansion in creep of monolithic materials. Thus the creep crack propagation is insensitive to the test temperature and the propagation rate is correlated well with the elastic energy release rate, Gmax in static and cyclic creep.

Ohtani, R, Kitamura, T, Uematsu, Y, & Hojo, M. "Mode I Delamination of Carbon Fiber Reinforced Thermoplastic Polymer Under Static and Cyclic Creep at Elevated Temperatures." High Temperature and Environmental Effects on Polymeric Composites. Ed. Harris, C, & Gates, T. 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959: ASTM International, 1993.