Systematic bonding zone investigations of injection molded wood-plastic-hybrid components

Wood is widely regarded as one of the most efficient lightweight materials for bending-stressed, planar components due to its high mechanical performance relative to its low density. To exploit these advantages in automotive applications, the wood-plastic-hybrid technology combines plywood structures with glass fiber-reinforced plastics through an injection molding process. A critical feature of this technology is the bonding zone, which governs structural integrity. This study systematically investigates the bonding zone performance as a function of geometry as well as manufacturing parameters regarding bonding zone area, injection speed (10 cm³/s and 40 cm³/s) and temperature (200 °C and 250 °C), the plywood species birch and beech and surface coatings (high-strength two-component (2K) polyurethane acrylic lacquer). Results show that birch achieves higher bonding performance than beech, though its distinct material characteristics require tailored processing strategies. Increased injection molding temperature and reduced rib base geometry significantly enhance bonding performance, while injection speed has a moderate effect. Comprehensive parameter optimization enables performance improvements of up to 164% by combining the most effective rib geometry with optimized injection speed, injection pressure and wood type. These findings close key research gaps regarding the influence of geometric and process parameters and the role of glass fiber-reinforced polymers in bonding zones. They provide a robust basis for selecting design strategies and process conditions tailored to specific requirements, advancing the wood-plastic-hybrid technology towards its implementation in vehicle components.