Effect of butt joints of prepreg plies on the tensile mechanical performance and fracture behavior of carbon/epoxy laminates

Abstract

This paper presents a numerical and experimental study on woven fabric reinforced composites containing co-cured plies joints in order to analyze the effect of butt joints staggered with different distances on the tensile mechanical behavior. Numerical simulations based on finite element method were performed to obtain the stress response of the specimens with embedded butt joints under tensile loads and the regions where the failures occurred for each staggered distance studied in accordance with Puck failure criterion. Tensile tests were executed on specimens whose staggered distances varied in 25, 15, 10, and 5 mm and the results of each family of laminates were compared with a baseline laminate (continuous fibers). The experimental results showed a reduction on the tensile failure load up to 26% compared to the reference laminate. Statistical analyses showed that the staggered distances of 15 mm presented better mechanical performance. SEM analyses revealed similar fractographic aspects on the fracture surface of the specimen with different staggered distances, characterized by a cohesive failure of the matrix originated by the butt joints, with a presence of a strong interfacial adhesion with the weft fibers and interfacial sliding with the warp fibers. The numerical simulation results presented a good agreement with the experimental ones.