High-Performance Natural Fiber Composites Made from Technical Flax Textiles and Manufactured by Resin Transfer Molding

摘要

In the present work it is shown that the resin transfer molding (RTM) is a beneficial technique to manufacture natural fibers into high-performance natural fiber composites. At first, three different types of weaves were produced by using low-twist flax yarns and standard-twisted flax yarns. Laminates based on the weaves and a petrochemical derived epoxy thermoset were fabricated by RTM process. For each laminate different numbers of plies (4, 5, 6, and 7) were used to achieve a broad range of v_f (from 32 % up to 55 %) which are having a pore volume fraction, v_p, as low as possible (min. 0.7 % - max. 2.7 %). For the laminates, flexural properties in warp and weft direction were determined (ISO 14125) and the effect of respective yarn type on flexural properties was investigated. The best properties were achieved for the laminate based on weave2 with V_f = 55 % (strength=303 MPa, modulus=19.3 GPa). When laminates were tested again after half of the year the modulus and strength were reduced, but the strain increased. The laminates were immersed into a water bath (ASTM D570) to test the influence of V_f and v_p on the water absorption behavior. The maximum water uptake (4-7 wt.-%) and the maximum thickness swelling (3-12 %) were observed for the samples with higher Vf. Laminates based on weavel were immersed again into the water bath to investigate the extent of deterioration of flexural properties with respect to water absorption at various time intervals. The laminates were tested immediately after removing from the water bath and after re-drying.