A Study of the Damage Accumulation Process in Poly(Aryl Ether Ketone Ketone) and Its AS4 Carbon Fiber Reinforced Composites. 1. Mechanical Properties

Poly (aryl ether ketone ketone), PEKK. is a relatively new high performance, high temperature thermoplastic polymer. PEKK is polymerized from diphenyl ether (DPE), terephthalic acid (T), and isophthalic acid (I). It has been shown in the past that PEKK with (T/I) ratios of approximately (60/40) and (70/30) demonstrate relatively slow rates of crystallization as compared with poly (aryl ether ether ketone) PEEK. The crystallization rate, and the subsequent crystal morphology, can be easily controlled in these systems by varying the crystallization temperature. While the crystallization behavior of PEKK has been extensively studied, the effect of crystallization condition on mechanical properties has not been investigated. In this paper, we study the effect of crystallization conditions on the mechanical properties and specifically the mechanisms which control the damage accumulation process and mechanical failure in the PEKK (60/40) and (70/30) systems and their AS4 carbon fiber reinforced composites. In general, quenched (amorphous) samples have the highest toughness and elongation to failure, while crystallized samples have higher strengths and moduli. The strengths and moduli of all crystalline samples are nearly the same, with the general trend being that samples crystallized near the peak crystallization temperatures have the highest moduli, while quenched samples have the lowest moduli.