Influence of laminate lay-up, hole size and coupling agent on the open hole tensile properties of flax yarn reinforced polypropylene laminates

The effect of laminate lay-up, open hole size and coupling agent on the open hole tensile properties of flax yarn reinforced polypropylene (PP) laminates were studied in this work. Unidirectional flax/PP laminates were prepared using a stacking technique, where newly developed interwoven fabric (flax/PP) and maleic anhydride grafted polypropylene (MAPP) copolymer film were used as a raw material and coupling agent respectively. The cross ply laminates (0/90/0)S showed high strength retention (98%) which ensured less notch sensitivity to the open hole profile. MAPP treated open hole samples achieved a reasonable improvement in tensile strength for all kind of laminate lay-up. Undrilled laminates tensile strength was improved by 14–17% due to MAPP treatment. Highest strength retention in MAPP treated sample was observed for cross ply laminates with 4 mm hole size, which was noted as 92%. Fractography studies confirmed the tensile fracture of fiber across the hole and good interfacial adhesion between fiber and matrix for MAPP treated laminates.