Investigation of joining of continuous glass fibre reinforced polypropylene laminates via fusion bonding and hotmelt adhesive film

Abstract As the demand for the lightweight and recyclability in automobile industry increases, continuous fiber reinforced thermoplastics (FRTP) have received extensive attention due to their excellent mechanical properties and fully recoverability. One of the ongoing challenges is to achieve sufficient joint strength in spite of the inertness (i.e. lack of functional groups) of some thermoplastics. In this current work, two joining techniques, including fusion bonding and hotmelt film were applied to bond continuously glass fiber reinforced polypropylene (PP/GF) composites. Firstly, operating procedures during the fusion bonding process of PP/GF laminates were focused and assessed. Tests were carried out to investigate the effects of fusion temperature, ply sequence of PP/GF substrates and fusion depth on lap-shear joint strength. The cross-section microstructure and fracture surface were observed by optical and scanning electron microscopy. Then, the adhesion of bonded PP/GF specimens using thermoplastic adhesive film was further investigated. The lap-joint strength and failure mode was compared with fusion-bonded counterparts. The results suggested that fusion-bonded of PP/GF exhibited higher joint strength while joining with hotmelt adhesive film experienced shorten processing period and lower molding pressure. Therefore, fusion bonding and hotmelt adhesive film provide low-cost, feasibility and recyclable adhesion methods, which are promising for joining of continuous fiber-reinforced thermoplastic composites.