Processing and mechanical characterization of a continuous flax fiber unidirectional lamina

Environment-friendly composites can be made by substituting synthetic reinforcements with plant fibers and using a biodegradable thermoplastic polymer as the matrix. The obtained material can be defined as a “green composite”. As the mechanical properties of vegetable fiber reinforced composites are typically low, one approach to achieve structural green composites is to orient the fibers in a single direction. This improves the longitudinal properties, although the transverse properties are still relatively low. In this study, unidirectional flax fiber reinforced poly(lactic acid) green composites are produced using a modified film stacking process with filament winding followed by hot pressing. Filament winding is selected because it permits a fiber pre-tensioning, which ensures good fiber alignment during hot pressing stage. Tensile tests are carried out following the ASTM D3039 standard. As awaited, the green composite shows significant anisotropic behavior, with transverse strength lower than that of the pure matrix, while the longitudinal properties show a marked improvement.