One-shot manufacturing of foam core sandwich composite without adhesive and its acousto-ultrasonic non-destructive evaluation

This study investigates the interfacial bonding reliability of CFRP/PVC foam core sandwich composites fabricated via a one-shot co-curing process without adhesive film, aiming to overcome the limitations of conventional multi-step bonding methods. Various types of carbon fiber prepregs were co-cured with a PVC foam core in a single-step process using either an oven or a hot press. To assess the bonding strength, mechanical testing, optical microscopy, and ultrasonic testing were conducted, focusing on the resin impregnation into the core. The results showed that the 3K and 12K configurations achieved sufficient bonding strength even without adhesive film, with failures mainly occurring within the foam core. The strengths of the adhesive-less composite was as acceptable as only 0–3.63% difference in average was observed with 5.75–9.34% weight reduction and 19.22–29.74% cost saving in compared to the conventional composite. In contrast, the UD and 6K configurations exhibited interfacial debonding because of insufficient resin impregnation to the foam core. Ultrasonic non-destructive evaluation analyzed the interfacial bonding at the interface. This study revealed the structural feasibility of adhesive-free one-shot co-curing. The proposed method enables reliable sandwich composite manufacturing without adhesive film, enhancing the lightweight and cost.