Multi-layered composite for custom production: integrating 3D-printed core with fiber-reinforced composites

Abstract This study investigates a novel hybrid multi-layer composite (MLC) that integrates a 3D-printed (3DP) core with technical fiber reinforcement and epoxy resin for custom-made applications, such as personalized knee braces. This approach aims to enhance the mechanical performance of 3DP components while eliminating the need for rigid molds. The MLC was fabricated by producing a flat PA12 3DP core via powder bed fusion, applying unidirectional glass fibers using tailored fiber placement (TFP), and encasing it in a braided biaxial carbon fiber sleeve. Flexural and tensile tests were performed. Micro-computed tomography (micro-CT) was used to analyze the internal structure. The mechanical behavior of the textile-reinforced composite layer was modeled using the Chamis model and classical laminate theory (CLT), with predictions compared to experimental results. The MLC exhibited a tensile strength of approximately 300 MPa, a modulus of 20 GPa, and a low average density of 1.4 g/cm 3 , resulting in a specific modulus comparable to that of aluminum alloys, thereby confirming its suitability for Lightweight structural applications. Both the Chamis and CLT models showed good agreement with experimental data, demonstrating their effectiveness in predicting and optimizing reinforcement structures. This study highlights the potential of utilizing 3D-printed cores as structural frames for fiber reinforcement. When combined with non-rigid molds, such as those used in infusion techniques, this novel approach eliminates the need for expensive production tools, significantly improving the cost-effectiveness of composite manufacturing. The proof of concept confirms the feasibility of MLCs for medical applications, such as lightweight, customized knee orthoses.