Effect of material and processing parameters on fiber pinning effect and resultant interfacial bonding strength of CF/PEEK bilayer parts in overmolding process

Abstract

The overmolding for thermoplastic composites is an integrated process that can manufacture multilayer parts with complex structures. However, the interfacial bonding strength between layers manufactured by different processes is weak. Here we study how material and process parameters affect the fiber pinning effect and thereby influence the interface binding strength of overmolded bilayer parts. The bilayer parts were prepared by overmolding the short-carbon-fiber-reinforced polyether-ether-ketone (SCF/PEEK) onto the hot-pressed woven-CF/PEEK (WCF/PEEK) laminates. An analytical model showed that the fiber pinning effect was dominated by the fiber content (Cf), interfacial temperature (Ti) and fiber orientation (αxx). The experimental results showed that a 32% increase in interlaminar shear strength (ILSS) of bilayer parts was achieved by regulating material and process parameters and optimizing the fiber pinning effect. The microstructural characterization shows that the Ti dominates the degree of resin fusion near the interface and thereby affects the fiber pinning depth indirectly. The Cf not only changes the amount of pinned fiber, but also affects αxx, which was confirmed by nano-CT scan.

Keywords

• A.Short-fiber composites
• B. Interfacial strength
• C. Representative volume element (RVE)
• D.X-ray computed tomography
• E.Overmolding process