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This study intended for the assessment of the stiffness, tensile and bursting properties of 3D printed auxetic sinusoidal patterns of different density and thickness deposited on the nylon fabric by means of fused deposition modeling (FDM) with the use of thermoplastic polyurethane (TPU) filament. Morphology, weight variation, flex stiffness, tensile property, Poisson’s ratio and bursting strength were analyzed for the characteristic evaluation of produced composite. The prototypes of two auxetic pattern repeat of 47 mm×43 mm and 20 mm×20 mm were developed named as low density (LD) and high density (HD) respectively. Both patterns were repeatedly combined to produce bigger size patterns and 3D printed with various thicknesses. Weight variation is found proportional to the density and thickness of 3D printed auxetic sinusoidal. Maximum up to 552 % weight increase was recorded for LD pattern and for HD 857 %. Flex stiffness increased with the rise of density and thickness of 3d printed auxetic sinusoidal pattern. Maximum flex stiffness for HD was 7.21 cm-g and for LD 4.73 cm-g. Warp direction is stiffest comparing with diagonal and weft in all cases. In case of tensile strength, a great extent of elongation was noticed due to the presence of auxetic sinusoidal 3D pattern and TPU filament. Maximum, more than 500 % elongation was showed by HD diagonal direction. HD patters exhibited more strength and toughness than LD patterns. In addition, warp direction is strongest and diagonal direction is weakest whereas the weft stays in between. Both LD-1.0 and HD-1.0 3D printed pattern showed negative Poisson’s ratio and the value was between -1.0 to 0. The enhanced bursting strength is found in HD patterns up to 1514 kPa comparing up to 1449 for LD. Thus, this study confirmed the excellent stiffness, tensile and bursting properties of HD 3D printed auxetic sinusoidal pattern/nylon composite over LD.

This study has investigated the physical properties of 3D-printable shape memory thermoplastic polyurethane (SMTPU) filament and its 3D-printed sinusoidal pattern obtained by fused deposition modeling (FDM) technology. To investigate 3D filaments, thermoplastic polyurethane (TPU) and SMTPU filament were examined by conducting infrared spectroscopy, x-ray diffraction (XRD), dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC) and a tensile test. Then, to examine the 3D-printed sinusoidal samples, a sinusoidal pattern was developed and 3D-printed. Those samples went through a three-step heating process: (a) untreated state; (b) 5 min heating at 70°C, cooling for 30 min at room temperature; and (c) a repeat of step 2. The results obtained by the three different heating processes of the 3D-printed sinusoidal samples were examined by XRD, DMTA, DSC and the tensile test to obtain the effect of heating or annealing on the structural and mechanical properties. The results show significant changes in structure, crystallinity and thermal and mechanical properties of SMTPU 3D-printed samples due to the heating steps. XRD showed the increase in crystallinity with heating. In DMTA, storage modulus, loss modulus and the tan σ peak position also changed for various heating steps. The DSC result showed that the Tg for different steps of the SMTPU 3D-printed sample remained almost the same at around 51°C. The tensile property of the TPU 3D-printed sinusoidal sample decreased in terms of both load and elongation with increased heating processes, while for the SMTPU 3D-printed sinusoidal sample, the load decreased but elongation increased about 2.5 times.

This study evaluated the shape memory and tensile property of 3D-printed sinusoidal sample/nylon composite for various thickness and cycles. Sinusoidal pattern of five thicknesses: 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, and 1.0 mm were 3D-printed on nylon fabric by the fused deposition modeling (FDM) 3D printer using shape memory thermoplastic polyurethane (SMTPU). Afterward, shape memory and tensile property was investigated up to 50 shape memory cycles. The study found that 3D-printed sinusoidal sample/nylon composite had a 100% shape recovery ratio for various thicknesses up to 50 cycles. The average shape recovery rate gradually decreased from 3.0&deg, /s to 0.7&deg, /s whereas the response time gradually increased with the increase of a 3D-printed pattern thickness. The stress and initial modulus gradually increased with the increase of the cycle&rsquo, s number. Thus, the shape memory property had a similar tendency for various cycles whereas the tensile property gradually increased with the increase of the cycle number. Moreover, this study demonstrated that this 3D-printed sinusoidal sample/nylon composite can go through more than 50 cycles without losing its tensile or shape memory property. This 3D-printed sinusoidal sample/nylon composite has vast potential as smart, reinforced, and protective clothing that requires complex three-dimensional shapes.