Numerical study for tensile strength prediction of unidirectional carbon fiber-reinforced composite considering fiber surface stress concentration

Abstract

The accurate tensile strength prediction of unidirectional carbon fiber-reinforced plastic composites (UD composites) requires approximate determination of the stress concentration on surviving fibers around a fiber break point. Here the stress concentrated on the intact fiber surface was determined by implementing double-fiber fragmentation tests in combination with a spring element model (SEM) simulation. The double-fiber fragmentation composites and the UD composites were elaborated with a T1100G-type carbon fiber and epoxy material, and tested to validate the proposed prediction method. The size scaling results, implementing a bimodal Weibull distribution for the statistical distribution of fiber strength, coupled with the results of the SEM simulation, designed to take into account the surface stress concentration, were reasonably consistent with the experimental data on the tensile strengths of the UD composites. Then, the proposed strength prediction procedure was applied to investigate the effects of the bimodal Weibull scale and shape parameters on the tensile strength of the UD composites. It was revealed that the degree of stress concentrated on the surface of fibers can be changed by modifying the bimodal Weibull shape and scale parameters. However, the carbon fiber with an improved scale parameters of 20% displayed enhancement to the composite strength by factor of ~1.07, and with an improved shape parameters of 20% showed enhancement by factor of ~1.04, indicating that the degree of enhancement in the tensile strength of the UD composite was limited.

Keywords

• carbon fiber
• polymer-matrix composite (pmc)
• fragmentation
• strength
• stress concentration