Flexural behavior of composites reinforced with innovative 3D integrated weft-knitted spacer fabrics

This paper undertakes to study the flexural behavior of 3D integrated weft-knitted spacer composites, under three-point bending. The integrated-knitted spacer fabrics were produced with various cross-sectional shapes on a computerized flat-knitting machine utilizing electrical grade glass (E-glass) fibers. The sandwich composites were manufactured by vacuum-assisted resin transfer molding using unsaturated polyester resin. Continuing the process, hand lay-up method was used to reinforce the face sheets of fabricated sandwich structure with glass woven fabrics. Bending performance of the produced composites was compared with polyurethane foam core sandwich composites. The results revealed that the cross-sectional shape has significant effect on the bending performance of the 3D integrated weft-knitted spacer composites. Also, the spacer reinforced composite with V-shape cross-section has the highest bending stiffness than composites with U-shape cross-section as well as polyurethane foam core sandwich composite. The failure modes of 3D integrated weft-knitted spacer composites include: core shear failure, compression failure of upper face sheet and tensile failure of lower face sheet.