A Sustainable Route for CF/PA6 Composite Waste: From Scrap to Solutions

The recycling of carbon fiber reinforced thermoplastics (CFRTP) is intrinsically complex, as it encompasses multiple interdependent variables, including the quality and heterogeneity of the incoming waste stream, as well as limitations on end-use applications, often restricted to nonstructural components, governed by the resulting mechanical and physicochemical properties of the recycled composite. Therefore, this work aimed to propose a sustainable route for the mechanical recycling of primary carbon fiber (CF)/polyamide 6 (PA6) composite blanket scrap preconsumer waste originating from the processing of components in the automotive sector. The waste was cut into specific geometric shapes, such as squares and triangles of two sizes (small: ∼5 cm; large: ∼10 cm), and placed in an aluminum mold, followed by hot compression molding to produce four reprocessed laminates. The laminates were inspected by ultrasound, and the volume fractions of reinforcement, matrix, and porosity were determined using the acid digestion method. The reprocessed laminates were evaluated for their thermal properties (differential scanning calorimetry, DSC, and thermogravimetric analysis, TGA), mechanical properties (interlaminar shear strength, ILSS, flexural strength, and Izod impact strength), and the morphological characteristics of the fracture surface. The results indicated superior values in the ILSS test, and the fracture surface morphology revealed satisfactory positioning, good adhesion, and interaction between the matrix and reinforcement in the reprocessed laminates. However, the patch arrangement and, mainly, the random orientation of the CF resulted in a drastic reduction in flexural performance. Laminate C, with smaller, triangular patches, resulted in greater impact resistance because it acted as a barrier to crack propagation and energy absorption. Reprocessing thermoplastic composite scraps proved feasible and satisfactory. Highlights: The reuse of carbon fiber reinforced thermoplastic composite scraps can be a viable solution for obtaining a secondary product.