Static strength of RTM composite joint with I-fiber stitching process

Resin transfer molding (RTM) is a mass production process that can replace autoclave processes, and composite lap joints are extensively used in composite structures. When a tensile load is applied to a single-lap joint, both shear and tensile peel stresses are generated owing to the eccentric load effect. Reinforcing the composite joint in the thickness direction can reduce the shear and peel stresses generated in the joint, which can contribute considerably to the increase in the strength of the composite joint. Several reinforcing methods have been developed to improve the directional properties along the material's thickness. Accordingly, a stitching process is typically used. However, the conventional stitching process has disadvantages because a) it requires complex equipment, and b) it cannot use highly elastic brittle fibers, such as carbon fibers. Recently, we proposed an I-fiber stitching process to minimize the bending of carbon fibers to prevent their fracture. In this study, composite, single-lap joint specimens were fabricated with RTM using an I-fiber stitching process, and their strengths were evaluated. The strengths of composite joint specimens fabricated at different stitching intervals and with the use of different patterns were compared with those of specimens fabricated without the use of the stitching process.