Interfacial adhesion strength between fibers of liquid crystalline polymer and thermoplastic matrix

The interfacial shear stress between fibers of liquid crystalline polymer (LCP) and various thermoplastics was evaluated using a single fiber composite test. Several ductile polymers such as polycarbonate (PC), polyethersulfone (PSF), and polyetherimide (PEI) were employed as a matrix polymer. The effects of matrix properties, welding time and welding temperature on the interfacial shear stress were examined. The interfacial shear stress increased abruptly at the initial welding time and became an equilibrium value, which implies that the wetting approached the equilibrium with increasing welding time. The equilibrium interfacial shear stress, tau decreased in the order of PSF/LCP, PEI/LCP, and PC/LCP. The debonding occurred at the interface and the plastic deformation of the matrix was not observed in the case of PC/LCP. However, the plastic deformation of the matrix near the interface was observed in the case of PSF/LCP. Through the measurement of polarity and compressive pressure, the polar interaction and compressive pressure were found to be the main interfacial adhesion mechanisms between LCP fibers and thermoplastic matrices.