Repeated impact behavior of multifunctional carbon fiber reinforced plastic composites sandwich structures with 3D printed novel rail interlocking core

The integration of energy storage function into structural components demands reliable mechanical protection while maintaining consistent electrical performance. This study aims to develop and evaluate multifunctional sandwich structures that can effectively protect batteries while maintaining structural integrity under impact conditions. A novel rail interlocking assembly method was introduced in this study that enables the interchangeability of sandwich structures considering energy storage functions and improved impact resistance. Multifunctional sandwich structures were implemented using 3D-printed corrugated cores with continuous carbon fiber filament, where the complex geometry includes a rail interlocking assembly designed for modular integration. Three different assembly methods (adhesive bonding, mechanical bolting, and an innovative rail system) were applied to fabricate sandwich structures consisting of carbon fiber-reinforced polymer skins and corrugated cores. The drop weight test was conducted on core supported (S) and non-supported (NS) cases to analyze the repeated impact behavior. The rail model exhibited superior mechanical uniformity between S and NS cases, showing only 3.6 % reduction in impact bending stiffness compared to significant degradations of 59.6 % and 36.3 % in adhesive and bolt models, respectively. While the adhesive model showed higher initial strength in supported conditions, its performance was drastically decreased under non-supported conditions, with a 63.1 % reduction in maximum load capacity. In terms of battery protection, the rail model maintained consistent charge–discharge capacity across all impact locations, with variations remaining within 2 %, whereas the bolt model showed 16.5 % greater capacity degradation despite experiencing lower peak loads.