This paper describes the analysis on the sound absorption characteristics of perforated membrane absorber. This study aimed to investigate the effect of perforation sizes and percentage of perforation areas on the membrane sound absorption characteristic. The effects of physical and material properties of the membranes such as thickness, Young's modulus and density were also investigated. The characteristics of the perforated membrane absorber were measured experimentally in terms of Sound Absorption Coefficient, α and Noise Reduction Coefficient, NRC by utilizing impedance tube method in compliance with ISO 10534-2 standard. The results showed that the peak value of absorption coefficient is determined by the density and thickness of the membranes. The perforation sizes also have a significant effect on the sound absorption coefficient and frequency range width. Optimal perforation size enhances the sound absorption performance of the membrane. Overall, the perforated membranes give better sound absorption coefficient and wider frequency range compared to the unperforated membranes

Abstract. This research focuses on the study of oblique impact on kenaf reinforced composite plate. This study summarizes modeling analysis of targets subjected to certain angle of collisions which ranging from 0"-45". Due to the low density, natural fiber such as kenaf fiber provides relatively good mechanical properties than glass fiber. Thus, natwal fibers have high potential for better reinforcement in light weight structures such as aircraft, automobile. In this research, the velocity impact analysis is conducted by using the commercial finite element analysis software, ANSYS. A few finite element models of the nonwoven composite panel and a rigid impactor is developed using ANSYS software. Experimental investigations in determining mechanical properties and validating purposes are conducted in earlier study by using Universal Testing Machine and High Speed Impact Puncher. Total force, total energy, deformation, and energy absorption of kenaf reinforced composite for oblique impact are analyzed and discussed. The rise of oblique angle will increase the energy absorption of the composite. IntroductionOver the past few decades, there has been a growing interest in the use of natural fibers in composite applications. These types of composites present many advantages compared to synthetic fibers, such as low tool wear, low density, cheaper cost, availability, and biodegradability [I-21. The response of composite materials to ballistic impact has been investigated by many researchers [3-61. It is obvious from the open literature that research on ballistic impact has been focused on the high performance fibres, metals and ceramics. In replacing metals and ceramics, syntactic fiber such as aramid fiber was used to produce more lightweight composites. But, it's consumes to increasing cost of composite to be produced. Therefore, many researches had been done on natural fiber based composite [4-71. Producing composite samples and performing the experimental will consume much time and cost. By using finite element analysis software, the natural composite model can be numerically created in short time and many tests can be virtually performed. But, it is important to do a validation process by comparing the experimental and numerical results obtained before any hither work conducted. Natural impacts in which the projectile strikes the target vertically (90" towards plane) are virtually nonexistent. Its normally occurs in oblique impact by which the impacting occurs in a certain angle of collision.

Natural fibres have the potential aspect to replace glass fibre reinforced composites. One of these fibers is kenaf. It is also one of the selected natural fibres that have bio resource profit regarding on their capability to absorb energy absorption especially. In order to prove the application of this fiber for the load-bearing application, the fiber in the form of yarn is weaved into fiber mat and reinforced with the plastic resin. This study focused on the twill yarn kenaf woven composite structure. Composites were prepared using the hand lay-up method with different type of orientation where the orientation is designed using Taguchi method. The hardened composites were cured for 24 hours in an ambient temperature before it was shaped according to ASTM D3039. The samples were then stressed uni-axially to obtain the stress-strain curves. The result shows the fiber orientations were significant factor in determining the performance of tensile strength. In this work, fiber mats are then optimized and the results showed that the values of tensile and modulus strength were 55.738 MPa and 5761.704 Joule, which is increased 3.77% and 4.23% for tensile strength and Young modulus, respectively. By comparing fracture mechanism before and after optimizations, there was clear decreasing fracture surface. It indicated that, the mechanical behavior performances of the twill woven kenaf reinforced composites can be effectively improved by this method.

is present project investigated the impact penetration response of woven jute fiber reinforced composites subjected to wide range of low impact velocities. Hand layout woven jute fibers are thermally compressed to ensure no internal defects formed in the composites. Six layers of woven jutes are stacked together using different fiber orientations [0/q/0]s. Low impact velocities are used ranging between 5 – 20 m/s. Force-time, force-displacement and energy-time curves are obtained automatically during the impact tests. The results are then discussed with considering the composite fragmentations and failure mechanisms. It is found that 00composite orientations capable to absorb sufficiently impact energy for 5 m/s but not for velocity greater than 10 m/s. When fiber orientations used between 15 – 450, the composite impact resistance increased indicating two significant peak forces. These peak forces represent different type of failure mechanisms occurred during the striker progresses.

This paper presents the combination technique in developing the woven kenaf fiber that is used as a new method to improve energy absorption performance. This method focuses on the effect energy absorption of angle orientation. Due to the low density, natural fiber such as kenaf fiber provides comparatively good mechanical properties. Thus, natural fibers have high potential for better reinforcement in light weight structures on automotive applications. Total force, total energy, and energy absorption of natural fibre reinforced composite for different type’s natural fibre and angle orientation are discussed and reviewed.