Abstract

This study investigates the tensile performance of layered PLA–TPU composites produced by multi-material additive manufacturing (MMAM) via fused deposition modelling (FDM). Although PLA–TPU is a widely used rigid–flexible polymer pair, tensile performance is often limited by weak interfacial bonding and limited evidence on how layer thickness, material ratio, and stacking sequence influence load transfer and fracture. A screening study of 30 layered specimens quantified the effects of layer thickness (0.1 and 0.2 mm), material ratio (33:67, 50:50, and 67:33 PLA:TPU), and stack order on apparent stiffness, ultimate tensile strength (UTS), elongation, and post-fracture failure features. PLA-rich configurations achieved high strength (up to 33.5 MPa) with semi-ductile failure behaviour, whereas TPU-rich configurations showed large elongations (up to 298%) but lower strength (12–14 MPa). Across the configurations tested, a 67/33 PLA/TPU laminate provided the best balance of strength and ductility, reaching an average UTS of 33.5 MPa with 7.7% elongation, consistent with improved interlayer load transfer despite the intrinsic surface-energy disparity between PLA and TPU. Overall, the results demonstrate that MMAM by FDM can combine dissimilar thermoplastics within a single build to achieve an adaptive mechanical response, while interfacial optimisation remains the primary constraint for further performance gains