Method to improve the bonding strength of polyethylene terephthalate core with glass fiber reinforced skins in a sandwich composite

Abstract Composite materials provide an alternative to conventional structural materials. Sandwich composites show high bending strength and superior strength‐to‐weight ratio. The major drawback in sandwich composites is debonding of skin from core, that causes failure of a component during the usage at different loads. To overcome this issue, the current work identifies a solution of introducing nylon screws (M6 × 32) to adhere firmly the skins consisting of glass fibers with PET (Polyethylene Terephthalate) core. The sandwich composites were fabricated by vacuum infusion process. Two flat sandwich composites were fabricated; one with nylon screws placed perpendicular to the skin and the other a plain sandwich composite. Mechanical characteristics of the specimens such as fracture toughness, flexural strength and shear strength were studied. Specimens with nylon screws showed 21.78% more fracture toughness compared to plain specimen. The presence of screws acts as hindrance to the propagation of cracks in the interfacial region resulting in the enhancement of debonding resistance of the specimens. Also, sandwich specimens with nylon screws exhibited 136% and 142% improvement in flexural and shear strength respectively when compared to plain sandwich specimens. The investigation of scanning electron microscope (SEM) images of tested specimens indicates strong interfacial bonding between skin and the core of specimens with nylon screws. Highlights Introduction of light‐weight nylon screws in z‐direction enhanced the bonding between face sheets and foam core. Sandwich composites with nylon screws exhibited superior bending and shear strength compared to plain specimens. Crack propagation in the interfacial region is restricted by the presence of nylon screws. Investigation of fractured specimens indicated a strong interfacial bonding in the specimens with screws.