This work investigates the dynamic impact response of Kevlar/oil palm empty fruit bunch (EFB) hybrid composite structures with/without gamma radiation under low velocity impact (LVI) and compression after impact (CAI) test. The layering pattern Kevlar/oil palm EFB/Kevlar (K/OP/K) was applied in this work. Irradiation with gamma ray with various doses were applied from 25–150 kGy. LVI results shows that hybrid Kevlar/oil palm EFBs (Kevlar/OPEFB) that were not irradiated have greater impact resistance as compared to irradiated hybrid Kevlar/OPEFB. It was also observed that the hybridization of Kevlar/OPEFB with gamma irradiation helped to improve the compressive residual strength of the composites. It was found that Kevlar/OPEFB hybrid composites with the layering sequence K/OP/K can withstand up to 35 J of impact energy, with the optimum gamma radiation dose at 50 kGy.

Hybrid composites with natural and synthetic fibers have captured the interests of many researchers. In this work, Kevlar/oil palm Empty Fruit Bunch (EFB)/Kevlar and carbon/oil palm EFB hybrid/carbon composites were prepared using hand lay-up technique by keeping the oil palm EFB fiber as the core material. The tensile properties which include tensile strength, tensile modulus and elongation at break were investigated. It is observed that the tensile strength and modulus for carbon/oil palm EFB/carbon hybrid composites were much higher as compared with Kevlar/oil palm EFB/Kevlar hybrid composites. However, the elongation at break for Kevlar/oil palm EFB/Kevlar hybrid composites exhibited higher value as compared to carbon/oil palm EFB/carbon hybrid composites and oil palm EFB/epoxy composites. The tensile strength for carbon/oil palm EFB/carbon hybrid composites is 93.6 MPa and the tensile modulus for carbon/oil palm EFB/carbon hybrid composites is 6.5 GPa. The elongation at break for Kevlar/oil palm EFB/Kevlar hybrid composites is 3.6%.

Glass fiber reinforced geopolymer composites (GFRGCs) materials are widely used in several industry especially in the aerospace industry due to their high strength to weight ratio, tremendous ablative properties, and high thermal stability. In the context of rocket insulation, the ablation properties of GFRGCs have attracted growing research interest. The extreme thermal stresses experienced during rocket launches and atmospheric re-entry demand advanced materials with high ablation resistance. Furthermore, recent studies were reported that incorporation of nanofiller such as nanoclay and multiwall carbon nanotubes (MWCNTs) can improve the ablation properties of GFRFCs. Nevertheless, whereas MWCNTs can increase mechanical strength and thermal conductivity and nanoclay is recognised for its capacity to increase thermal stability, their combined impact on the ablation performance of GFRGCs has not been well investigated. This study aims to elucidate the effect of incorporation of both nanoclay and MWCNT to the ablation properties of GFRGC. A systematic approach, such as Response Surface Methodology (RSM), is utilized to optimize the composite formulation in identifying the optimal combination of these additives and their interaction with the glass fibers and geopolymer matrix. GFRGC samples were fabricated using hand lay-up technique and the ablation properties were evaluated through fire test. Through RSM, both nanoclay and MWCNTs has signifanct effect on the back temperature of the sample. Besides, the experimental result shows that GFRGC has the lowest temperature at the back of the sample with 3% nanoclay and 7% MWCNTs with value of 306.741°C. The thermal conductivity value of this sample also resulted in the lowest value of 0.069 W/mK compared to the other sample. This finding can contribute to the development of promising insulation materials for high thermal application.

This study investigates the effect of reheating on previously deposited layers in material extrusion (MEX) 3D printing, commonly known as Fused Deposition Modeling (FDM), considering the combined effects of deposition sequence (unidirectional and bidirectional) and key process parameters, including printing temperature, printing speed, and layer height. Two temperature measurement methods were used to record changes during printing, and the results from local and global approaches were compared. The temperature of the interface between the first deposited layer and the build platform was measured with thermocouples. The findings show that the reheating effect at the first layer fades with increasing build layer, with no further increase in heating profile after the eighth layer, regardless of the process parameters investigated. The measured minimum temperatures at the investigated location remained above the glass transition temperature, T_g, which is critical for bonding and polymer chain rearrangement to continue taking place. Printing temperature was found to be the strongest observed factor influencing reheating, as it provides the heat for conduction into previous layers. Deposition sequence also played an important role, with bidirectional deposition leading to higher reheating and 25–50% more layers above the crystallization temperature, T_c. Overall, the results confirm that deposited roads undergo cyclic heating, and understanding the influence of process parameters on reheating is important for interpreting bond formation in MEX 3D printing.

Glass fiber reinforced geopolymer composites (GFRGCs) materials are widely used in several industry especially in the aerospace industry due to their high strength to weight ratio, tremendous ablative properties, and high thermal stability. In the context of rocket insulation, the ablation properties of GFRGCs have attracted growing research interest. The extreme thermal stresses experienced during rocket launches and atmospheric re-entry demand advanced materials with high ablation resistance. Furthermore, recent studies were reported that incorporation of nanofiller such as nanoclay and multiwall carbon nanotubes (MWCNTs) can improve the ablation properties of GFRFCs. Nevertheless, whereas MWCNTs can increase mechanical strength and thermal conductivity and nanoclay is recognised for its capacity to increase thermal stability, their combined impact on the ablation performance of GFRGCs has not been well investigated. This study aims to elucidate the effect of incorporation of both nanoclay and MWCNT to the ablation properties of GFRGC. A systematic approach, such as Response Surface Methodology (RSM), is utilized to optimize the composite formulation in identifying the optimal combination of these additives and their interaction with the glass fibers and geopolymer matrix. GFRGC samples were fabricated using hand lay-up technique and the ablation properties were evaluated through fire test. Through RSM, both nanoclay and MWCNTs has signifanct effect on the back temperature of the sample. Besides, the experimental result shows that GFRGC has the lowest temperature at the back of the sample with 3% nanoclay and 7% MWCNTs with value of 306.741°C. The thermal conductivity value of this sample also resulted in the lowest value of 0.069 W/mK compared to the other sample. This finding can contribute to the development of promising insulation materials for high thermal application.