Microstructure-driven flexural and fracture behavior of CFRP/wood sandwich composites: role of tracheid orientation

Abstract

: Wood is a highly anisotropic material, where its orientation and stacking in the core of CFRP composites significantly affects the energy dissipation and damage evolution in CFRP/wood core composite structures. The effect of wood tracheids orientation in the core of CFRP/balsa wood composites was investigated by considering two configurations, where in the first (Configuration A), the tracheids of the whole wood core were aligned perpendicularly to the CFRP sheets. Configuration B is composed of two wood layers, where the tracheids were aligned perpendicular to the CFRP sheets at the layer adjacent to the CFRP sheets, while the middle layer tracheids are perpendicular to the CFRP face sheets. Results demonstrated different damage initiation mode under flexural loading, where delayed delamination initiation at CFRP face sheet occur in configuration A, while early CFRP face sheet fiber breakage for configuration B due to the higher deformability and reduction of stress concentration at the CFRP face sheets. Configuration A showed 18%, 44%, and 20% higher flexural modulus, bending strength, and damage initiation strain than configuration B. However, 19% and 42% higher initiation and propagation fracture toughness for configuration B than A was achieved due to the orientation of wood fibers being in the crack propagation.