Analysis and experiment on DCB specimen using I-fiber stitching process

Several studies related to the reinforcement of composite structures in the through-thickness direction have been conducted recently. In this study, a new reinforcement process is proposed based on previous experimental results; the proposed novel process involves the stitching of T-joints and one-stitched specimens. The need for additional analysis was established under standard DCB tests, for better understanding. Finite element modeling (FEM) results were compared after performing mode I interlaminar fracture toughness tests, using different stitching patterns, for analyzing the through-thickness strength, using reference laminates without stitching. The stitching patterns were defined as 2 × 2 and 3 × 3, where the upper and lower head of the non-continuous stitching process (I-fiber) was shown to strongly affect the through-thickness strength of the laminate. To design a numerical model, cohesive parameters were required for defining surface-to-surface bonding elements using the cohesive zone method (CZM) and for simulating the crack-opening behavior from the DCB test.