Evaluation of stress concentration caused by fibre failure using multi-fibre composites: Stress concentration factors and interfacial property

Stress concentration caused by a fibre failure is assessed by testing a multi-fibre model composite. The specimen consists of ECR-glass and Kevlar fibers embedded in a vinylester matrix, and the fibers are embedded parallel to each other at a constant distance. The vinylester/glass-fibre interfacial property is varied to investigate relationship between the interfacial property and stress concentration factor (SCF). Micro Raman spectroscopy (MRS) is used to directly capture the stress concentration profiles in the intact Kevlar fibre induced by a fibre break of ECR-glass fibre. From experimental results, the stress distribution of the Kevlar fibre is found to have its maximum values at two points which are adjacent to the fibre-break point and the interfacial debonding tip, respectively. An elasto-plastic shear-lag analysis is employed to predict the values of SCF, and the theoretical values of SCF are proved to be in good agreement with the experimental results. The values of SCF are found to be strongly affected by the interfacial property, and the optimal value of the interfacial strength is discussed.