The aim of this work was to study the effects of natural fiber type and loading content on the sound absorption efficiency of natural rubber (NR)/treated natural fiber composite foams. This was investigated by measuring the cell characteristics of composite foam, sound absorption coefficient (SAC), and viscoelastic behavior. Bagasse (BF) and Oil Palm (OPF) fibers were treated with sodium hydroxide (NaOH) solution and the optimal treatment conditions for BF and OPF were determined by varying treatment times and NaOH concentrations. Potassium oleate (K-oleate) was used as a blowing agent to create open-cell NR foam. The results indicated that the most suitable NaOH concentration for both BF and OPF was 10%wt. and optimal treatment times were 30 and 10 min, respectively. At low fiber loadings, the addition of treated BF and OPF resulted in a decrease in the average cell size and an increase in the number of foam cells. As loading increased above 5%wt., cell size and cell number exhibited the opposite trends. Both treated BF and OPF enhanced the sound absorption efficiency of NR foams, especially at medium and high frequencies. NaOH treatment improved the interfacial bonding between the matrix and natural fibers, and increased the roughness on the surface of BF and OPF, leading to an enhanced ability for BF and OPF to absorb sound waves. The results indicated that treated BF was more effective than treated OPF for increasing SAC values. Type and dispersion of fiber and viscoelastic behavior were important factors on SAC of composite foams more than cell characteristic.

This paper shows the feasibility of replacing the SPCC steel with glass fiber reinforced Nylon composites for the manufacturing of tensioner pulley. Three series of Nylon (Nylon 66, Nylon 46 and Nylon 46 with PTFE) reinforced with 30wt% of glass fiber were investigated. Finite Element Analysis (FEA) was carried out to simulate the stress distribution and to predict the maximum stress located on the pulley component. It was found that all Nylon composites had higher tensile modulus than SPCC steel, while the SPCC steel exhibited higher tensile strength. FEA demonstrated that the maximum stress on Nylon composite pulley was lower than the SPCC steel pulley, however these stresses were higher than yield stress of materials. The addition of supporting rib can reduce the stress concentration to lower the yield stress of materials. Finally the performance of Nylon composite pulley was considered. Pulley with plain-surface bearing was meet the criteria for endurance test, however, the interfacial adhesion between bearing and Nylon composite pulley can be improved by glued and gouged surface. According to the experimental results, glass fiber reinforced Nylon composites can be the representative materials of replacing SPCC steel for tensioner pulley.