Effect of Scrap Configuration on the Tensile and Flexural Properties of Grinding-Free Recycled CF/PA6 Composites

Abstract The increasing demand for lightweight, high-performance materials in the automotive sector has driven the use of carbon fiber/polyamide 6 (CF/PA6) composites. This study proposes a grinding-free recycling route based on the reassembly of CF/PA6 composite cutouts into a controlled laminate configuration, followed by hot compression molding. Three configurations were investigated: S21 (two layers of 1 mm-thickness square cutouts), S13 (one layer of 3 mm-thickness square cutouts), and R21 (two layers of 1 mm-thickness rectangular cutouts), all containing 85 wt % CF/PA6 scraps and 15 wt % neat PA6 powder. The recycled laminates were characterized by ultrasonic inspection, differential scanning calorimetry (DSC), acid digestion for volumetric fraction determination, tensile and flexural testing, and field-emission gun scanning electron microscopy (FEG-SEM) analyses. Ultrasonic inspection and acid digestion showed that the S13 configuration exhibited the highest structural homogeneity and the lowest void content. In contrast, S21 and R21 presented higher void fractions, as confirmed by ultrasonic maps, acid digestion results, and FEG-SEM observations. Despite the higher void content, S21 achieved the highest tensile strength, probably due to the more efficient stress distribution throughout the laminate. Fractographic analyses revealed good fiber–matrix interfacial adhesion, as well as typical aspects observed in the fracture surfaces of thermoplastic polymeric composites, including plastic deformation, fiber pullout, and matrix-rich regions. Overall, the results demonstrate that the proposed grinding-free recycling approach enables the reuse of CF/PA6 waste in multilayer architectures in applications that do not require high structural performance.