Mechanical and Environmental Durability of High Performance Bio-based Composites

Sammanfattning: This study is an initial step within the on-going project on development of high performance bio-based composites with improved mechanical (fatigue) and environmental (elevated humidity and temperature) durability. In the presented thesis the performance of cellulosic fibers (flax and regenerated cellulose), bio-based resins (Tribest, EpoBioX, Palapreg, and Envirez) and their composites under exposure to elevated humidity has been studied. Composites reinforcement was in a form of fiber rovings and fabrics to manufacture uni-directional and cross-ply laminates. Water absorption experiments were performed at different humidity levels to measure apparent diffusion coefficient and moisture content at saturation. Effect of chemical treatment (alkali and silane) on fibers as protection against moisture was also subjected to study. The comparison of results for pristine resins and composites showed that primarily cellulosic reinforcement is responsible for moisture uptake in composites. However, fiber treatment did not improve moisture resistance in composites significantly. Mechanical testing was carried out in order to estimate the influence of humidity on behavior of these materials. Results were compared with data for glass fiber and epoxy, as reference materials. The results indicated that some of the bio-based resins and composites with these polymers performed very well and have comparable properties with composites of synthetic epoxy, even at elevated humidity.