Investigation of Compression, Impact and Post-impact Behavior of Carbon/Flax Bio-hybrid Laminates: Effects of Stacking Sequence and Fiber Hybridization

This study investigates the compressive, low-velocity impact (LVI), and compression after impact (CAI) behavior of carbon/flax bio-hybrid fiber-reinforced polymer (bio-HFRP) laminates, with the aim of enhancing damage tolerance and sustainability in structural composite applications. Four 15-ply hybrid configurations, symmetric, asymmetric, and sandwich type, were fabricated with controlled stacking sequences of carbon and flax fibers. These laminates were subjected to quasi-static compression testing, as well as impact tests at four energy levels (30 J, 45 J, 60 J, and 90 J), followed by CAI evaluation to assess residual strength. The results revealed that incorporating flax into hybrid laminates alters mechanical response characteristics: flax layers enhanced energy absorption and improved post-impact strength retention, while carbon outer plies contributed to increased stiffness and surface protection. Among the configurations tested, the sandwich laminate, with carbon skins and a flax core, demonstrated the most favorable balance between peak impact resistance, residual compressive strength, and overall structural performance. Detailed failure analysis showed a transition from brittle failure in carbon-rich zones to progressive matrix cracking and delamination in flax-dominant regions. The study confirms that fiber hybridization, when combined with optimized stacking design, can significantly improve mechanical efficiency and damage tolerance while contributing to the environmental goals of composite engineering. These findings position carbon/flax bio-HFRPs as a promising solution for sustainable, high-performance applications in aerospace, automotive, and other advanced industries.