Moisture Absorption and Fracture Toughness of PEEK Polymer and Graphite Fiber Reinforced PEEK

Tests were conducted to determine the moisture absorption characteristics of PEEK 150P polymer and APC-2 composite exposed to humid air, and to evaluate the effects of moisture content and crystallinity on the fracture toughness. Tests were con ducted with PEEK 150P specimens having 30, 34, and 43 percent crystallinities and with APC-2 specimens having 17 and 21 percent crystallinities. The weight gains of these speci mens were measured during exposure to air kept at relative humidities ranging from 60 to 100 percent and temperatures ranging from 140 to 200°F. The values of the maximum moisture content and diffusivity were deduced from the weight gain data. Empirical cor relations were established for the maximum moisture content and for the diffusivity. The room temperature fracture toughnesses of PEEK 150P and APC-2 were measured. For the conditions of the tests the fracture toughness was found to be unaffected by crystallinity and by moisture content.