Fiber/Matrix Interaction in Carbon/PEEK Composites

Abstract

This paper deals with the fiber/matrix interface in carbon /PEEK compos ites. It is found that although interphase crystallinity is essential to ensure good interfacial strength in carbon /PEEK composites, it is not the primary factor responsible for the crea tion of fiber/matrix interaction in this composite. The results suggest that such interaction is a result of several complex mechanisms such as matrix adsorption on the fiber surface, fiber/matrix reaction leading to chemical bonding, and crystallization of the interphase. The concept of adsorption proposed by Brady and Porter for the carbon/polycarbonate system seems to be valid for interpreting the evolution of the short beam shear strength with residence time, as described by a Langmuir-type expression. The temperature de pendence of the formation of the fiber/matrix interaction, as measured by the short beam shear strength, is also found to follow an Arrhenius equation with an activation energy of about 324 kJ mol-1. The high value of the activation energy and the irreversibility of the interaction process suggest that chemisorption could be a dominant mechanism, since, in the range of processing temperatures for carbon / PEEK composites, there is effective modification of the matrix (chain scission and crosslinking) as well as thermal degradation leading to reactive species.