Development of a novel flax soy-based polyurethane prepreg composite

High performance composite materials are mostly synthesized from non-renewable resources with a detrimental environmental impact. In this work an innovative flax fiber-reinforced soy-based polyurethane composite prepreg was developed from a soy-based polyol crosslinked with glycerin and isocyanate. The flax reinforcement was manufactured by binding unidirectional flax strings with short flax fibers. Composite prepregs were fabricated using a three rolls mill and oven pre-curing to obtain a beta stage. Vacuum assisted molding was used to manufacture laminates with a fiber volume fraction up to 41 %. Electron beam and optical microscope images of the composite cross-section indicated an adequate microstructure. Tensile strength (209 MPa), flexural strength (231 MPa), and short beam shear strength (25 MPa) demonstrated that the composites had good specific mechanical properties comparable with composites containing glass fibers studied in previous works, while having a significantly lower expected environmental impact. These properties demonstrate the appropriateness of the eco-responsible composite material.