Tensile performance of multi-material sandwich structures fabricated by multi-nozzle fused deposition modeling using PLA, ABS, and HIPS

• ·The PAP structure responds to changes in raster width, print speed, and layer thickness the most consistently. • ·The structural strength of PAP and APA increased significantly when the fiber orientation was parallel to the tensile load, especially at raster angles of 45° and 90° with a print direction of 0°. • ·Although filler density affects strength, the effect is not always directly correlated. • ·The selection of the right molding structure and parameters is key to optimizing mechanical strength • ·In particular, better layer fusion and microstructural integrity were demonstrated in APA composites. • ·Most process parameters exhibit a non-linear influence on tensile strength, indicating the existence of an optimal threshold at which maximum strength is achieved, exceeding this threshold will result in a marked reduction in mechanical performance. • ·Each analyzed structure can be used as a reference for product development, depending on the specific needs of the intended application. This study investigates the tensile and interfacial bonding behavior of six multi-material sandwich structures APA, PAP, HPH, PHP, AHA, and HAH fabricated using a multi-nozzle fused deposition modeling (FDM) printer with PLA, ABS, and HIPS. A systematic variation of seven process parameters layer thickness, raster angle, build orientation, raster width, print speed, infill density, and core composition was conducted using a Taguchi L27 orthogonal array. Among all configurations, APA exhibited the highest tensile strength of 48.03 MPa and a modulus of 796.17 MPa, outperforming PAP (42.07 MPa) and HPH (38.07 MPa) by approximately 10–15%, attributed to superior interlayer fusion and balanced material synergy. Raster angles aligned at 45° and 90°, particularly when combined with 0° build orientation and moderate raster width, further improved the mechanical performance, especially in PLA- and ABS-based structures. Microscopic and fractographic observations reinforced these findings, revealing that APA exhibited denser layer fusion and fewer interfacial voids, contributing to its superior structural integrity. PETG was excluded due to poor adhesion with PLA and ABS under comparable conditions. These findings highlight how parameter optimization and strategic material pairing in sandwich configurations enhance performance, indicating their applicability in lightweight structural applications such as UAV frames, protective enclosures, or biomedical supports.