MODELING TRANSVERSAL SUPPORT FROM NANOFIBER Z-THREADS TO A CARBON FIBER BY FINITE ELEMENT ANALYSIS OF A CFRP UNIT CELL

摘要

Carbon fiber reinforced plastic (CFRP) laminates' compressive behaviors are fiber dependent and matrix sensitive. Void or defect areas are often generated during the CFRP manufacturing process, which cause internal unbalanced stresses, instability, and eventually fiber breakage and buckling, and the fiber failure propagation. In this study, carbon-nanofibers (CNFs) z-threaded CFRP (ZT-CFRP) structure was investigated regarding the potential roles of CNF z-threads in inhibiting the stress concentration effect and the carbon fiber transversal displacement due to unbalanced internal stresses. The CNFs, zig-zag threading through the array of carbon fibers, provide interlaminar and intralaminar reinforcement and are expected to provide additional transversal support for individual carbon fibers to resist unbalanced internal stresses and mitigate the fiber failure modes and the failure propagation. This internal stability enhancement may help improve the CFRP laminate's fiber buckling failure resistance. The finite element analysis (FEA) was performed on an assembly of ideal ZT-CFRP representative volume elements (RVEs) (i.e., unit cells) to understand the transversal support enhancement mechanisms of CNF z-threads in both the in-plane transversal direction (Y-direction) and the through-thickness direction (Z-direction). The results showed improvements in supporting the carbon fiber in both directions while the Z-directional improvement is 73% more effective than the Y-directional improvement.