Flexural and impact properties of flax woven, knitted and sequentially stacked knitted/woven preform reinforced epoxy composites

In this article, plain woven, rib knitted and sequentially stacked rib knitted/plain woven, flax fabric reinforced epoxy composites are investigated for their flexural and impact properties. The effect of lay-up angle and the number of preform layers on the above-mentioned properties are also studied. The composite laminates were processed by hand lay-up technique using 2 and 4 mm thick spacers and cured under pressure of 3 bar for 2 h at 50 degrees C, followed by curing in an oven at 120 degrees C for 1 h. Specimen preparation and testing were carried out as per ASTM standards. The results indicate that the woven preform reinforced laminates perform better in both flexural and impact properties for all the lay-up angles and thicknesses investigated in this study. Among the sequentially stacked knitted/woven preform reinforced laminates, specimen with knitted preform as the skin layers exhibited better flexural and impact properties. The data obtained show a tendency of lower flexural and impact values with increase in number of preform layers for all lay-up angles with the exception of lay-up angle [0 degrees/ + 45 degrees/-45 degrees/0 degrees]. At low fibre volume fraction, the sequentially stacked knitted/woven preform reinforced laminates were found comparable to woven preform laminates.