Effect of fiber diameter on stress transfer and interfacial damage in fiber reinforced composites

Abstract

In this work, the effect of fiber diameter upon the strength, stiffness, and damage tolerance of a fiber-reinforced polymer composite laminate structure was investigated. Three cases were considered, in which the fiber diameters of 16, 8, and 4 microns were used. A fiber volume fraction of 32% was assumed in each model. Micromechanical, shear-lag, and progressive damage analyses were performed using finite element models of the structure, which was subjected to tensile loading in the fiber direction. Fiber-matrix load transfer efficiencies and the stress distributions near broken fibers within the composite structure were investigated and results compared for each fiber diameter. In addition, the effect of fiber diameter upon the initiation and evolution of fiber-matrix interfacial damage and debonding was studied using cohesive interface elements. For a specified volume fraction and load condition, as the fiber diameter was decreased the load transfer efficiency and effective stiffness of the broken fiber model increased. Also, as the fiber diameter was decreased, the initiation of damage at the fiber-matrix interface occurred at greater stresses and the subsequent growth of damage was less extensive. These results indicate that, for the same total mass, the performance and damage tolerance of composite materials may be enhanced simply by using smaller diameter fibers.