Influence of Fiber Fillers on The Ballistic Properties of Epoxy and Polyester Resins: A Review

Ballistic shields are considered a tactical measure to protect high-risk areas. Due to their advanced design, they provide effective protection against fragments and projectiles, reducing fatalities and preserving lives under adverse conditions. Therefore, researchers have focused on the importance of materials in the production of these shields, emphasizing three main aspects: lightweight properties, cost, and ballistic resistance. They have used polymeric materials reinforced with fillers to enhance ballistic resistance, competing with metal and ceramic shields. The present research has examined studies involving epoxy and polyester as core materials, and Kevlar, natural fibers, carbon fibers, and carbon nanofibers as reinforcements. Comprehensive research indicated that Kevlar-reinforced epoxy resins enhance impact resistance, energy absorption, and ballistic resistance; the research has achieved improved results in configurations of 4 to 10 layers or 6 to 22 layers when combined with rubber or alumina additives. Polyester resin composites provide excellent impact resistance, especially when combined with 20–33 layers of Kevlar; however, some natural fibers offer enhanced multi-impact resistance and ballistic protection compared to standard Kevlar. The mechanical and ballistic properties of epoxy and polyester resins are significantly enhanced by incorporating carbon fiber and carbon nanotube (CNT) reinforcements. CNT additions to epoxy resins have been shown to enhance dynamic properties and energy absorption; at a 4% CNT concentration, the intensity of the shock wave can be reduced by up to 33%. CNTs at a 1% concentration produce optimal energy absorption. In contrast, ramie fibers outperform Kevlar in terms of cost-effectiveness and weight, achieving cost reductions of up to 95% and enhancing scratch depth resistance through additional layers of reinforcement. Sisal, jute, and other natural fibers provide cost-effective alternatives to Kevlar.