Effect of resin modification on the impact strength of glass-polyester composites

Fiber-reinforced plastics (FRP) are nowadays used commonly for constructions subjected to impacts of different energies and velocities, therefore the problem of their impact resistance is very important. One of the methods to improve impact properties of the composites is resin modification with elastomeric phase. In this study the effect of resins addition on properties of composites of unsaturated polyester (UP) resins with glass fibers was investigated. At the first stage, the properties of Polimal 109-32K UP resin modified by the addition of reactive liquid rubbers were tested. The wettability of glass fibers by resin compositions was also tested. Composites were then prepared with the addition of 2 and 6 phr of epoxy or vinyl terminated butadiene-acrylonitrile rubbers (ETBN or VTBN, respectively), as well as 5 and 15 wt. % of Polimal 150 elastic UP resin. These composites were subjected to mechanical tests. Impact properties were tested using Charpy method, as well as by a ballistic impact using a gas gun. After the ballistic impact, damage extent and residual strength as well as water leakage through the composites were evaluated. The damage was also investigated under a microscope. The damage extent was confirmed to be linearly dependent on the impact energy. The addition of rubber was, found to decrease the damage extent and increase post-impact residual strength, as well as decrease water leakage rate.