Low energy impact behavior of unidirectional and cross-ply flax/epoxy laminates and comparison with similar glass/epoxy laminates

Abstract

Unidirectional (UD) and cross-ply flax and glass fiber reinforced composites (FFRC and GFRC)are tested under four out-of-plane low velocity impact loads. A hybrid flax reinforcement was used, denoted UD-mat, which is made of a UD layer of continuous flax fibers bound to a flax fiber mat layer. For the mat binder, two types of short flax fibers are considered: unmodified fibers and refined ones. The laminates made ofrefined fibers show the highest permanent and maximum displacements. Moreover,the peak load for the unidirectional FFRC with refinedfibers is lower than that with unmodified fibers, for example it is 25% lower at 11 J. When comparing with flax fiber laminates, the absorbed energy and energy absorption ratio are on average 40% lower for glass laminates but less damage is observed. Several failure modes are observed in the flax laminates, while the main failure of the glass/epoxy laminates is delamination.