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The study aims to investigate the effect of different infill pattern structures on the energy-absorbing characteristics of single filament wound carbon fiber-reinforced plastic tubes, single polylactic acid and hybrid carbon fiber-reinforced plastic/ polylactic acid tubes under quasi-static axial compression condition, which were fabricated using filament winding and additive manufacturing techniques. Five infill pattern structures of single polylactic acid tubes and hybrid tubes were studied and compared on their energy-absorbing characteristics, which referred to normal, triangle, square, hexagonal and tetrahedral patterns. It concluded that the effect of the infill pattern structure had a significant influence on energy-absorbing characteristics of single polylactic acid and hybrid carbon fiber-reinforced plastic/polylactic acid tubes. For pure polylactic acid tubes, the triangle infill pattern tube represented the highest values of energy absorption (EA) of 0.75 kJ, specific energy absorption (SEA) of 28.50 J/g, compressive strength and modulus of 69.72 MPa and 1.40 GPa, yield strength of 27.80 MPa, peak crushing force (Fpeak) of 23.13 kN and mean crushing force (Fmean) of 18.82 kN. For the hybrid carbon fiber-reinforced plastic/polylactic acid tube, tetrahedral infill pattern tube showed the highest values of EA with 0.99 kJ, SEA with 29.66 J/g, Fpeak with 22.68 MPa and yield strength with 29.91 MPa. Energy absorption interaction (EAinteraction) and interaction ratio (φe) of all specimens were evaluated, which showed that the tetrahedral infill pattern tube recorded the highest of all hybrid tubes with 259.92 J and 35.72 %. The result revealed that the tetrahedral pattern displayed better crashworthiness in terms of crushing force efficiency (CFE), EA and SEA in the hybrid structure, which had greater potential to apply as energy absorbers. Moreover, triangle and square infill patterns of hybrid tubes provided the negative interaction effect results, which conducted lower energy-absorbing characteristics compared to individual tubes, respectively.

Fibre-metal laminates (FMLs) offer advanced improvements over current available structural materials due to the excellent mechanical properties. In this work, the dynamic behaviour of the carbon fibre/epoxy, glass fibre/epoxy, aluminium 2024-T0, and fibre metal laminates were carried out. Furthermore, the different type of reinforced composites in FMLs and the effect of the layer sequence of metal layers were investigated. The composite laminates have been manufactured by a hot press machine. The free vibration tests were conducted to determine the dynamic characteristics of the samples. The accuracy of the experimental results was verified by comparing the numerical analysis results. The results indicate that the effect of thickness and the layer sequences of metal layers have a significant effect on the natural frequency of the FMLs.

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