The Effect of a Coupling Agent on the Impact Behavior of Flax Fiber Composites

The effects of a coupling agent on the behavior of flax fiber-reinforced composites have been investigated by testing the specimens under both quasi-static (QS) indentation and high-velocity impact loading. The specimens are manufactured embedding a commercial flax fiber fabric in a polypropylene (PP) matrix, neat and premodified with a maleic anhydride-grafted PP, the latter acting as a coupling agent to enhance the interfacial adhesion. QS compressive tests were performed using a dynamometer testing machine equipped with a high-density polyethylene indenter having the same geometry of the projectile employed in the impact tests. The impact tests were conducted setting three different impact velocities. Digital image correlation maps of out-of-plane displacement were employed to compare the specimens with and without the coupling agent. The QS testing results indicate that the coupling agent has an enhancing influence on the bending stiffness of tested flax composites. The testing results show that the coupling agent improves the mechanical behavior by decreasing the out-of-plane displacement under impact loading. This approach gives rise to new materials potentially useful for applications where impact performance is desired while also providing an opportunity for the incorporation of natural fibers to produce a lightweight composite.