Damage mechanisms under static and fatigue loading at locally compacted regions in a high pressure resin transfer molded carbon fiber non-crimp fabric

Manufacturing defects are an issue of composite manufacturing processes. Local clamping is proposed to prevent fiber washout during high pressure resin transfer molding of non-crimp fabrics. At the clamping regions the material is compacted by through-the-thickness compression. The current work investigates the mechanical performance of such regions under static and fatigue loading. Two typical manufacturing defects are intrinsic to the compacted regions: fiber undulation and resin starved/dry spots. In component tests the thereby generated damage is monitored using 3D digital image correlation and the complete processes of damage initiation and propagation are analyzed. Static and low cycle fatigue failure are dominated by fiber undulation at the edges of the compacted region, triggering matrix damage and delaminations. High cycle fatigue is dominated by decreasing fiber matrix adhesion within the compacted region, leading to longitudinal splitting and progressive fiber failure. Identification of damage initiation is supported by numerical finite element simulations.