Prediction of the Strength for Unidirectional Composites, considering Fiber, Matrix and Interface

Abstract

The present paper reports a simulation of the probabilistic strength of unidirectional composites, where three elements of composites, i.e., fiber, matrix and interface are taken into consideration. The fracture mechanism of fiber reinforced plastics (FRP) includes fiber/matrix interface debonding and matrix cracking in addition to fiber breakage. Fracture toughness values were adopted in deciding the fiber/matrix interface debonding and the matrix cracking. The present simulation can realize a zig-zag mode of the fracture surface in the unidirectional composites. By varying the interfacial adhesive strength (fracture toughness) from very low to very high, the strengths of seven types of unidirectional composites were calculated by a Monte Carlo Simulation. The results showed that the strength of unidirectional composites generally increased with increasing the interfacial strength. This result means that reliable load transmission is essential for FRP, as is widely accepted. However, at the same time, the highest strength of unidirectional composites appeared when the adhesion of the fiber/matrix interface was slightly weak compared with the completely tight adhesion. This result suggests that a material design of the fiber/matrix interface is important to get good-quality composites.