Multi-Layer Laminate of Fibreglass Thermoplastic Composite Reinforced with Fused Filament Fabrication TPU Layers

Thermoset fibre-reinforced composites are increasingly used in high-end industries such as aerospace or autosport. As the demand for more sustainable materials strengthens, thermoplastics have emerged as one key focal point due to their potential recyclability, and for more efficient and sustainable applications. To change, replace, or expand the use of thermoplastic composites, new approaches to their manufacture and mechanical performance must be tackled and tailored to each application, structure or engineering challenge. The present study is focused on design, manufacture and test of advanced multi-layer laminated composites made by thermoplastic polypropylene (PP) prepreg matrix reinforced with continuous woven fibreglass. The composite laminate was subjected to interlayer toughening through thermoplastic polyurethane elastomer (TPU) layers manufactured by Fused Filament Fabrication (FFF). The manufacturing process was iteratively optimized, resulting in successful adhesion between layers. Three composite configurations were produced: baseline Glass Fiber Prepreg with Polypropylene (GFPP); and two multi-layer composites, GFPP with solid TPU layers (GFPP-TPU) and GFPP with honeycomb structured TPU layers (GFPP-TPU-HC). Thermogravimetric and Differential Thermal Analysis were also conducted on the specimens. TPU layers contributed to increase the thermal decomposition temperature of the specimens in which it is included. Specifically, the GFPP-TPU and GFPP-TPU-HC composites exhibited higher thermal stability compared to the baseline GFPP, attributed to the stabilizing effect of the TPU layers. Tensile testing was conducted on FFF additively manufactured TPU specimens, while all laminated composites were tested in three-point bending. The results demonstrated the potential of the developed composites. The addition of solid TPU layers to GFPP decreased the flexural modulus but limited the plastic deformation in the specimens that did not undergo delamination during the testing. In contrast, GFPP-TPU-HC exhibited improved geometric consistency and, on average, a less variable and increased flexural modulus.