| Within the past several years, researchers have detected the presence of a third "phase" between the bulk fiber phase and bulk matrix phase in a polymeric matrix composite. This finite-thickness region--termed the interphase--possesses mechanical, physical, and chemical properties that are distinct from the fiber and matrix constituents. Thus, the interphase embodies the characteristics of the fiber/matrix bond, including the strength and stiffness of the bond. In essence, the interphase represents the composite system, since it defines the level of synergistic interaction that occurs between the load-carrying fibers and the binding matrix material.;Recent interest in the interphase has spawned international conferences and a technical journal devoted to its study. Despite this spate of research, some very fundamental questions about the interphase have remained unanswered. One such question is: "What is best for the ;Two formidable challenges await those who wish to correlate the strength of the interphase to the mechanical performance of polymeric matrix composite materials. First, one seeks to systematically alter the interphase in order to exploit this variable. In this study, fourteen material systems representing permutations of four carbon fibers, three matrix systems, percentages of fiber surface treatment, and three sizing conditions have been examined. Secondly, one needs to quantitatively characterize the properties of the resultant interphase in order to correlate the bond condition to the composite's mechanical behavior. This investigation utilizes two techniques, the Continuous Ball Indentation Test and transverse flexure testing, as a means of interrogating the strength of the interphase.;The influence of the interphase on the tensile and compressive strength and modulus of cross-plied laminates possessing a center hole is investigated. Unnotched angle-ply ( (;Fully-reversed (R = ;Having observed the formative role played by the interphase in the performance of these laminates, an attempt is made to introduce variables representing the interphase into micromechanical models of composite behavior. |
