The aim of this research is to investigate the effect of alkali treatment and steaming on mechanical properties of Snake Fruit frond fiber. The presence of surface impurities and a lot of hydroxyl groups makes natural fiber less compatible for composite materials reinforcement. Efforts to remove the impurities can be done by physical, chemical and mechanical treatments. This paper reports the treatment of Snake Fruit frond single fiber by subjecting it to alkali treatments with 2%- 8% NaOH for 2 - 6 hours at room temperature. The treatment is then followed by steaming at a pressure of 2 bars in 1 hour. Results show that the treatment of alkali and the alkali-steaming combination can increase cellulose percentage. The tensile tests show that this type of treatment in combination resulted in the higher tensile strength compared to untreated fiber. There is a significant increase in tensile strength with increasing alkali percentage. However, the further increase in the percentage of alkali solution will result in decreasing tensile strength. The highest value of tensile strength after treatment was 275 MPa with 6 hours treatment at alkali percentage of 2 %.

Weight plays a significant role in the automotive and aerospace fields due to the demand of lightweight material structures. A lighter body in weight (BIW) and in structure can reduce fuel consumption, lessen emissions, and support the SDGs 9, 11, 12, and 13. Therefore, polyurethane (PU) foam is suitable for applications that require low weight. The characteristics of hybrid polyurethane-graphite micro were successfully evaluated in this study. Several tests have been used to characterize these structures, such as, compression, hardness, density, surface evaluation, and FTIR analysis. The results showed that the expansion and shrinkage variations lead to different shapes at specific ratios. Compression tests show that the highest value occurred at 0.84 kN, with a 4:1 ratio found in pure PU foam without any reinforcement. PU foam with 2% graphite filler showed the highest results at the 4:1 ratio with a value of 0.45 kN. Furthermore, the highest hardness test result was 37.7 SHD. Density testing indicates that the highest value is obtained from specimens with a 4:1 ratio of 0.077 g/cm³. FTIR testing reveals that adding graphite as a filler alters the chemical bonds during the formation of solid PU foam. Surface observations show that adding graphite as a filler influences the variation in material structure formation. All the evaluation has tended to conclude the present combination as suitable for lightweight structures applications.

The growing demand for complex structures, energy absorption, and mechanically strong materials has led to the exploration of innovative composites. This study focuses on the manufacture, characterization, and evaluation of PLA+ reinforced with woven glass fiber. Using Fused Filament Fabrication (FFF) 3D Printer technology, the effects of adding woven glass fiber were examined through a tensile test with Digital Image Correlation (DIC)-induced, flexural, Charpy impact resistance, Shore D hardness, Differential Scanning Calorimetry (DSC) thermal tester, and SEM morphological tests. Results showed that adding four layers of glass fiber significantly improved mechanical properties: tensile strength increased by 85% to 95.44 MPa, flexural strength by 13% to 91.51 MPa, and impact resistance by 450% to 15.12 kJ/m². However, a reduction in hardness and thermal resistance was noted due to chemical interactions. These findings suggest potential applications of PLA+ composites in high-strength products for vehicle bumpers in the automotive industry and shin pads in the sports industry.

Plug welding was used on the parts of the structure in which spot welding cannot be implemented, such as the complex structure and the construction with the profile stiffener. The objective of the present work is to define the static and fatigue behaviors of the plug-welded dissimilar metal welds between carbon steel and austenitic stainless steel with different thicknesses because the detailed recommendations on it were limited. Carbon steel SS400 with a thickness of 3.0 mm and 1.0-mm-thick austenitic stainless steel SUS304 were plug welded using varied hole diameter in a range of 7 to 13 mm where the welding current and the diameter of welding wire were kept constant at 80 A and 1.0 mm, respectively. The welding joints were exposed to tensile shear tests, and the transition of interfacial fractures to tearing fractures was defined as the optimum condition. Tensile peel, fatigue, and corrosion fatigue tests were carried out on the optimum specimens. The optimum plug welding joints were obtained at the hole diameter of 8 mm where the tensile peel and tensile shear load bearing capacity were 8.6 and 17.2 kN respectively. The endurance limit of fatigue conducted in air was 2 kN, whereas corrosion fatigue samples at this load fail at about 1,000,000 cycles. AWS's formula for plug weld can be applied to the plug-welded dissimilar metal welds between carbon steel and austenitic stainless steel with different thicknesses. Endurance limit of this joint in corrosive environments is about half of the endurance limit in normal environments.

Aluminum alloys emerged as one of the materials used in manufacturing automotive car bodies due to their advantageous properties such as high strength-to-weight ratio, relatively low cost, high ductility, and high corrosion resistance. However, joining aluminum alloys using fusion welding poses serious problems due to the high solubility of hydrogen gas, which causes porosity in welding metal. Subsequently, solid-state welding, such as friction stir welding (FSW), has been considered a porosity-free aluminum joining method. However, the method has limitations, such as low flexibility and the need for a complex clamping system. It is particularly problematic when welding plates. It causes the welding process to be carried out twice on opposite sides, resulting in longer production times. This study designed and assembled a one-step double-side FSW apparatus to address this challenge and conducted welding trials with various welding parameters. During the welding trial, the upper and lower tool rotation varied at 900/900 rpm and 1500/1500 rpm. As a result, one-step double-side FSW was successfully used for welding 6 mm aluminum without any porosity defects. Faster tool rotation results in a wider heat-affected area and higher tensile strength. In addition, the hard test showed that the one-step double-side FSW process had a lower hardness compared to the hardness of the base metal.

This research aims to investigate the performance of crashworthiness parameters and behavior of bamboo fibers reinforced epoxy matrix composite tube with chamfering angle 45° at one end. The quasi-static compression testing was applied axially on the specimen to investigate the response of force-displacement during progressive collapses. The machine used in this experimental testing was the Shimadzu concrete compression testing machine with capacity 2000 KN. The load-displacement curve and the history of the crushing mechanism are presented and discussed. The result shows that bamboo fibres reinforced epoxy matrix composite tube with chamfering angle 45^o at one and can absorb energy amount 6.03 KJ for 50 mm displacement of cross-head. The others parameters, such as peak load, average load, crush force efficiency, and specific energy absorption was with values 170 KN, 117.43 KN, 0.69, and 21.91 KJ/kg, respectively. Besides those findings, the failure mechanisms show the combination modes, i.e. progressive failure and catastrophic failure modes.