A novel micro-mechanical model for continuous carbon fiber-reinforced composites: Effect of fiber surface roughness on mechanical behaviors

Abstract

The fiber surface roughness determines the interface contact between carbon fiber and resin of composites, and its effect is crucial to be investigated. This study develops a micro-mechanical model considering the surface morphology of carbon fibers to examine the impact of microscopic geometric features on the macroscopic mechanical behaviors of composites. The morphological characteristics of the carbon fiber surface were well captured through image processing based on the microscopically scanned images of fiber cross-sections to determine the average depth-to-width ratio of grooves on the fiber surface. Further, based on statistical analysis, the proposed model considering surface roughness of carbon fibers were developed to evaluate the effective mechanical properties of composites. Then, both the experimental and theoretical results demonstrated that the proposed model exhibits a 3 % reduction in the relative error for predicting the transverse modulus when compared to the standard model indicating a minimal effect of surface roughness on the mechanical responses in this case. However, further numerical analyses using an average depth-to-width ratio twice that of the initial proposed model revealed a 4.18 % increase in the transverse elastic modulus. By calculation, the transverse tensile strength was 39.43 MPa when using the proposed model, demonstrating an increment of 5.1 % in strength when compared to that using the standard model.