Photoelastic and numerical analyses of the stress distribution around a fiber in a pull-out test for a thermoplastic fiber/epoxy resin composite

The stress distribution in a polyester fiber/epoxy matrix model composite subjected to pull-out test was investigated through photoelasticity and elastic-plastic numerical analysis using finite element (FE) simulations. A photoelastic technique was used to obtain isoclinic fringe patterns, which were employed to construct a pair of orthogonal families of principal stress trajectories for a pull-out specimen. It was found that the trajectories of the maximum principal stress tend to converge at points where either the maximum interfacial shear stress is located or there is stress concentration. The FE simulations proved to be a powerful tool that allowed understanding the 3D stress distributions, in areas located near the embedded fiber, where principal directions were influenced by radial stresses, effects of Poisson's ratio, reduction of fiber diameter and plasticity. The FE simulations could be extended to quantify stress fields in other single-fiber test configurations. POLYM. COMPOS., 39:E2397-E2406, 2018. (c) 2017 Society of Plastics Engineers