Direct Reuse of Uncured CFRP Prepreg Scraps for Structural Applications: Experimental Qualification and Numerical Validation of an Automotive Battery Case

The high demand for fiber-reinforced composite materials generates large quantities of uncured prepreg waste, still in pristine condition, usually landfilled or incinerated. Among the various established recycling routes, direct reuse of these scraps represents an attractive strategy to reduce both raw material consumption and manufacturing waste, while preserving the original constituents' properties, and avoiding energy-intensive recovery processes or the use of hazardous chemicals, thus moving an energy demanding industry toward sustainability. This work aims to demonstrate that when properly processed, prepreg scraps can be converted into a recycled material with high potential also for structural applications. A full-scale Electric Vehicle (EV) battery pack has been manufactured from uncured prepreg scraps and tested according to UN 38.3 vibration test T.3 with frequency sweep cycles to assess vibration response, mechanical robustness, and post-test structural integrity. The battery enclosure successfully completed the test with no structural failure, debonding, or functional degradation. A limited reduction of approximately 3% in the first resonance frequency was observed throughout the test campaign, suggesting only minor stiffness degradation while preserving the structural integrity of the component. A numerical model of the battery pack was also developed and validated against experimental data, showing good agreement; a further comparison with a traditional glass-fiber composite demonstrated equivalent performance in terms of safety and structural resistance, supporting the feasibility of replacing conventional composites with recycled patch-based laminates. These results demonstrate that direct reuse of uncured prepreg scraps can deliver structurally reliable load-bearing composite components for demanding automotive applications.