Measurement and analytical validation of interfacial bond strength of PAN-fiber-reinforced carbon matrix composites

Carbon/carbon composites are well suited to high-friction applications due to their excellent mechanical and thermal properties. Since interfacial shear strength is critical to composite performance, characterization of fiber/matrix interface is a crucial step in tailored design of composites. This article presents a hybrid experimental/analytical study to evaluate the interfacial shear strength (IFSS) of PAN-fiber-reinforced carbon matrix composites. Microstructure was studied by light and high-resolution transmission electron microscopy (HRTEM). A series of push-out tests were conducted to examine the fiber/matrix debonding process. The residual fiber displacement was confirmed by scanning electron microcopy (SEM). The validity of the calculated IFSS value was demonstrated by a simplified analytical approach, where the components contributing to the measured displacement were analyzed considering the mechanics of the indentation. The method described in this article has been successfully used for determining the IFSS of PAN-fiber-reinforced carbon matrix composites.