Study of fiber length and fiber-matrix adhesion in carbon-fiber-reinforced polypropylenes

Abstract

Carbon-fiber-reinforced polypropylenes often exhibit insufficient mechanical properties because of low affinity between the carbon fibers (CFs) and the matrix resins. From the viewpoint of designing materials with better properties, it is important to control the interfacial properties. In this study, the interfacial properties are quantified in terms of the interfacial shear strength (IFSS), and the relationships among the IFSS, composite strength, and impact resistance are evaluated. When the fiber length is sufficiently short (as in injection-molded materials), the composite strength and impact resistance improve with increasing IFSS. On the other hand, when the fiber length is longer, the impact resistance improves with decreasing IFSS. Longer CFs with low IFSS require higher energy to pull out from the matrix resin than that required for interfacial debonding.