Constructing quasi-vertical fiber bridging behaviors of aramid pulp at interlayer of laminated basalt fiber reinforced polymer composites to improve flexural performances

Basalt Fiber Reinforced Polymer (BFRP) composites have huge potential application respects for some civil fields due to enough strength/modulus to weight and low cost by replacing carbon fiber composites. Aiming at the issues in the Resin-Rich Region (RRR) and Interfacial Transition Region (ITR) of fiber reinforced polymer composites, the characteristic Aramid Pulp (AP) fibers with micro-fiber trunk and nano-fiber branches were manufactured into multiple non-woven ultra-thin interleaving at the interlayers of BFRP composites via compression molding to reinforce the flexural strengths and elastic moduli. AP fibers were introduced into RRR to form interleaving at the interlayer, the brittle epoxy adhesive layer was improved and enabled to avoid cracking under a low external load. Free fiber branches of AP were also embedded into BF layer to construct quasi-vertical fiber bridging behaviors in ITR, stronger mechanical interlocking was created to prevent crack propagation along the bonding interface of BF/epoxy. Three-point bending testing results showed the interleaving film with 4 g/m² AP exhibited the best effect among various areal densities and yielded average 315.75 MPa in flexural strength and 21.38 GPa in elastic modulus, having a 63.4% increment and a 47.1% increment respectively compared with the bases. Overall, the simple and low-cost AP interleaving is confirmed as an effective method in improving interlayer structure and flexural performance of BFRP composites, which may be considered to manufacture high-performance laminated fiber reinforced polymer composites in civil aviation industry.