Enhancing mode-I and mode-II fracture toughness of carbon fiber/epoxy laminated composites using 3D-printed polyamideinterlayers

The aim of this study is to improve the delamination resistance of traditional carbon fiber/epoxy composites by incorporating 3D-printed polyamide (PA) interlayers. Reference and PA-interleaved carbon fiber/epoxy laminates were manufactured by vacuum assisted resin transfer molding technique. The effect of the 3D-printed PA interlayers on both Mode-I and Mode-II fracture toughness of the carbon fiber/epoxy composites was evaluated. Additionally, the shear and flexural properties of the composites were assessed through short-beam shear and three-point bending tests. Acoustic emission data was gathered to study the influence of PA interlayers on the failure modes of composite laminates. Dynamic mechanical analysis (DMA) was utilized to study the thermomechanical response of the reference and PA-reinforced composites. The study revealed a substantial increase in critical energy release rates for both Mode-I and Mode-II (GIc and GIIc) by 43.5% and 81.2%, respectively, as compared to the reference composites. The primary mechanism for the improvement was attributed to crack bridging and plastic deformation of the PA filaments in the interlaminar region. Additionally, there was a 17.4% increase in the interlaminar shear strength The DMA results indicated a significant increase in tan-delta values, while the inclusion of 3D-printed PA interlayers did not affect the glass transition temperature. Nonetheless, the 3D-printed PA interlayers adversely affected the flexural properties of the composites, owing to increased thickness and reduced fiber volume fraction. The utilization of AE technique for detecting and analyzing damage in hybrid composite systems can assist researchers and engineers in enhancing their performance and prolonging their durability.