Interfacial strain distribution of a unidirectional composite with randomly distributed fibers under transverse loading

The micromechanical approach was used to investigate the interfacial strain distributions of a unidirectional composite under transverse loading in which fibers were usually found to be randomly packed. Representative volume elements (RVEs) for the analysis were composed of both periodic fiber arrays, such as a square array and a hexagonal array, and a random fiber array. The finite element analysis was performed to analyze the normal, tangential, and shear strains at the interface. In order to verify the RVE for describing a random fiber array, the generated RVE was statistically compared with the one constructed from typical images of a transverse cross-section of a unidirectional composite. Since the strain distributions at the interface experienced periodic characteristics along with its circumference, the Fourier series approximation with proper coefficients was utilized to evaluate the strain distributions at the interface for the periodic and random fiber arrays with respect to fiber volume fractions. From the analysis, it was found that the random arrangement of fibers had a significant influence on the strain distribution at the interface, and the strain distribution in the periodic arrays was one of special cases of that in the random array.