Investigation of the performance of the structure and energy absorption in sandwich panels of PLA/TPU manufactured by the FFF technique

Sandwich structures are often used in the automotive, marine, aerospace, and many other industrial sectors due to their desirable performance properties, energy absorption, and ability to reduce the weight of parts. Multilayer composite materials also provide various design possibilities, making it simple for producers to fabricate intricate parts. One of the most popular additive manufacturing technologies for producing complicated objects is fused filament fabrication (FFF). In this study, sandwich samples with a dual-core of polylactic acid (PLA) and thermoplastic polyurethane (TPU) were fabricated by FFF technique in three different configurations, including cylindrical, honeycomb, and tetrahedral truss cells. Their properties were determined and investigated through tensile, three-point bending, Izod impact, microhardness tests, and scanning electron microscopy. The results were compared with samples manufactured with monolithic PLA. The results demonstrated that sandwich structures with TPU cores had a high-energy absorption capability. In comparison to monolithic PLA samples, these materials’ ultimate elongation and impact strength were dramatically enhanced. However, TPU cores had lower flexural and tensile strengths than samples with PLA cores. The structure's shape significantly influences both its strength and energy absorption characteristics. Firstly, tetrahedral truss core samples revealed that the samples’ elongation climbed considerably and exceeded three times with the deposition of TPU as the inner core compared to monolithic PLA. Last but not least, in flexural testing, sandwich panels with honeycomb manufactured of PLA/TPU showed the ultimate strain unit to be about 0.08, twice as much as samples made of monolithic PLA. The lowest impact resistance and the amount of energy absorbed before collapsing were demonstrated by monolithic PLA with a honeycomb inner core. Regarding energy absorption, dual sandwich panels with PLA/TPU, including cylindrical and tetrahedral truss cores, showed the best results.