Exploring the flexural and impact properties of pure flax/epoxy and Kevlar/flax/epoxy composites through experimental and numerical analysis

Hybrid composites offer a viable alternative to conventional composites in terms of reduced cost and environmental impact. This study investigated the effect of hybridizing flax with Kevlar on the flexural and impact properties of Kevlar/flax/epoxy composites using three-point bending, drop-weight, and Charpy impact tests. The tested specimens were made of unidirectional flax fibers (F) and woven Kevlar fibers (K) in four configurations: unidirectional flax/epoxy [016F] (UFE), angle-ply flax/epoxy [+/- 454F]S (AFE), woven Kevlar/unidirectional flax/epoxy [0-902K/06F]S (UKFE), and woven Kevlar/angle-ply flax/epoxy [0-902K/+/- 453F]S (AKFE). The three-point bending test results showed that the ultimate strength and the flexural modulus of the UKFE increased by 15% compared to pure UFE and by more than threefold for AKFE compared to AFE laminates. Additionally, the results of the drop-weight test revealed a significant increase in the impact force by 30% for both unidirectional and angle-ply laminate configurations. Similarly, Charpy test results indicated a 60% improvement in the impact energies of the flax laminates. The predictions of the proposed finite element model agreed very well with the experimental results. These findings demonstrate the effectiveness of hybridizing two layers of Kevlar onto flax/epoxy composites in enhancing the composite's impact and flexural properties.