Effect of Mat Design and Manufacturing Parameters on the Mechanical Properties of Needle-punched Flax Fiber-reinforced Composites.

- Flax is one of the natural fibers currently pursued as a renewable source to replace glass fibers in polymer composites. Vacuum Assisted Resin Transfer Molding (VARTM), used to manufacture medium to large sized composites for transportation industries, require non-woven mats. The manufacturing (permeability) and structural (volume fraction (V f ), and thickness) requirements for the non-woven mats used in VARTM process, should be met. Unlike glass, flax mats are neither optimized, to yield desired permeability for easy impregnation, compaction, final part thickness, fiber volume fraction, and properties, nor are commercially manufactured in North America. Developing this knowledge is the focus of this study. Effect of needle punch density on flax fiber mat structure (areal density, V f , thickness, and permeability) and the effect of consolidation pressure while manufacturing composites on its structure (V f , part thickness) and properties was studied. The tensile strength and tensile modulus of needle-punched flax composites, manufactured using VARTM pressure as well as compression molding pressures (subsequent to VARTM molding), were measured and used in evaluating the effect of various parameters identified above. Mats manufactured with 20, 30, and 72 punches/cm 2 needle punch density were used. The permeability decreased with increase in the punch density. The consolidation of, fiber volume fraction in, and properties of composites manufactured using mat with loosely bound (72 P with 2 mm needle punch depth) fibers were higher than the tightly bound mats (20P and 30P with 8 mm needle punch depth).