Overmolded hybrid composites of polyamide-6 on continuous carbon and glass fiber/epoxy composites: 'An assessment of the interface'

In this study, we investigated overmolding of thermoplastics on thermoset composites as an alternative joining method, in order to enable production of hybrid thermoset composites. Specifically, we explored the parameters affecting adhesion between overmolded polyamide-6 (PA6) and continuous glass or epoxy fiber-reinforced composites. Three main factors were studied: type of reinforcing fiber (carbon and glass), moulding temperature during overmolding process (30 degrees C and 80 degrees C), and application of peel-ply on composite surface. Overall, peel ply application, higher mould temperature (80 degrees C) and composite surface with carbon fiber reinforcement resulted in better adhesion. Three point bending, dynamic mechanical analysis (DMA), roughness, and contact angle measurements reveal strong bonding. Scanning electron microscopy (SEM), micro-computed tomography (micro-CT) images and energy-dispersive X-ray spectroscopy (EDS) results support the improvement due to peelply application. Findings from thermal analysis confirm the effect of reinforcement material type on crystallinity of overmolded polymer and underline the essential role of contact surface chemistry.