Experimental and numerical analysis of transverse stitched T-joints in bending

An experimental and numerical analysis has been undertaken to investigate the bending strength of transversely stitched T-joints using a fiber insertion process. Finite element analysis (FEA) was performed on the structural joint to predict failure loads and experiments were conducted to determine the modes of failure and ultimate failure strength. Joint parameters including local web thickness, flange thickness, number of rows of stitching, and resin types were varied to determine the effect on joint performance. Fractographic examination was performed to investigate the joint failure mechanisms. Significant results of this experimental study include: adding a local web pad-up to the T-joint bend specimen increases the bending strength of the joint; increasing the number of rows of stitching increases bending strength; adding a local flange pad-up to the T-joint bend specimen only marginally increases joint failure strength; initial joint failure occurs by matrix cracking initiating at the resin rich corner fillet and propagating inward toward the transverse stitching; and ultimate joint failure occurs by fiber breakage and/or fiber pullout.