Influence of different geometric arrangements of discontinuous reinforcement on tensile strength and fracture behavior of carbon/epoxy laminates

Abstract

This study presents the influence of different geometric arrangements of butt joint formed by plain weave fabric prepreg layers on mechanical and fracture behavior of carbon/epoxy laminates tested under tensile loading. The experimental test results showed a reduction of up to 17% on the tensile failure load, due to the presence of the discontinuity in the reinforcement, when compared to the continuous fiber reinforced composites. However, statistical analyses demonstrated that the different staggering methods of the butt joints did not affect considerably the tensile mechanical behavior of the laminates. The stress concentration in the embedded joint regions was observed by finite element analysis results, which predicted the tensile failure load and also the failure region, according to Hashin criterion. SEM analyses revealed that all specimen configurations exhibited fracture in the butt joint regions, with the occurrence of cohesive failure of the matrix originated in the co-curing process, associated with a strong interfacial adhesion with the fibers. This behavior evidences a high interfacial strength of the co-cured plies joints, which is attributed to the good quality of the prepreg material associated with the efficiency of the laminate manufacturing process. The numerical studies showed a good fit with the available experimental results regarding tensile failure load. Therefore, the implemented finite element model proved to be adequate to accurately predict the tensile strength of plain weave fabric laminates containing layer joints.