Bond strength and bond mechanism of injection over‐molded woven carbon fiber/PEEK‐short carbon fiber/PEEK composite components

Abstract A weak interface is formed between injected plastic and substrate during the injection over‐molding process. This study investigated the effects of mold temperature and melt temperature on the bond strength of injection over‐molded components, which were produced by injecting short carbon fiber reinforced polyether‐ether‐ketone (SCF/PEEK) onto the surface of woven carbon fiber reinforced PEEK (WCF/PEEK) laminate substrate. The results show that the interfacial laminar shear strength (ILSS) increases significantly from 15.8 to 50.0 MPa as the mold temperature raises from 190 to 260°C. The ILSS increases first and then decreases with melt temperature raises from 380 to 420°C, achieving a maximum value of 44.4 MPa at 410°C melt temperature. Crystallinity analysis and microscopic observations indicate different bonding modes are formed at the interface. The matrix tangling appears in the matrix enrichment area, interlocking, and tangling appear in the pits and weak tangling and cracks occur on the fiber surface. The mold temperature affects the ILSS by changing the crystallization property and the connection mode in the interface, while the melt temperature affects the ILSS by changing the area of the matrix entanglement. The relationship between the process conditions—interfacial microstructure—interfacial mechanical performance was discussed.