Effects of reinforcement configuration and densification on impact strength of wood veneer/polyester composites

Abstract

Current energy absorbers in industrial applications are made of metals or fiber-reinforced polymers using glass and carbon fibers. These materials are extremely stiff and strong but exhibit low-energy absorption when subject to the impact load. Other issues in the use of these materials are their high cost (fiber-reinforced polymer) and weight (metal). Wood reinforcements on the other hand are light weight and economic but less stiff. This study investigated the impact resistance and fracture patterns of wood-reinforced polyester composites using a drop-weigh impact test and considers the potential of using wood as a natural reinforcement in the manufacturing of polymer composites. Densified and un-densified Douglas-fir veneers were used to create three different mat configurations: woven, cross, and unwoven (unidirectional) mats. A total of 350 specimens were tested following ASTM D5420, and their impact resistance was calculated using the staircase method. Scanning electron microscopy was used to examine the resin distribution and its penetration into the reinforcement. Additionally, light micrographs of the veneers before and after densification were examined to determine the effect of densification on the cell-wall structure. Glass fiber-reinforced polymer samples had significantly higher impact resistance than the wood composites. Densification of the veneer did not significantly improve the composite performance. The effect of reinforcement configuration on the final performance of the wood–polyester composites, however, was significant with the woven, and cross configurations having notably higher impact energy than unidirectional composites.