Thesis Abstract

The abstract of the research project is as follows Natural fiber composites have gained significant attention in recent years due to their potential as sustainable and environmentally friendly alternatives to traditional synthetic fiber composites. In this study, the effect of polymer composition, specifically the ratio of high-density polyethylene (HDPE) in the composite, on the mechanical properties of natural fiber composites was investigated. Different ratios of HDPE and natural fibers were compounded using a twin-screw extruder and compression molded into test specimens. Tensile, flexural, and impact tests were conducted to evaluate the mechanical properties of the composites. The results showed that the mechanical properties of the composites were significantly influenced by the polymer composition. Increasing the ratio of HDPE in the composite led to improvements in tensile strength and modulus due to the higher stiffness and strength of the polymer matrix. However, excessive HDPE content resulted in a decrease in tensile strength, which could be attributed to poor interfacial adhesion between the hydrophobic polymer and hydrophilic natural fibers. In terms of flexural properties, increasing the HDPE content also improved the flexural strength and modulus of the composites. This enhancement can be attributed to the better load transfer between the fibers and the polymer matrix. However, a higher HDPE ratio led to reduced flexural strength, indicating a decrease in the composite's ability to withstand bending loads. Impact strength tests showed that the impact resistance of the composites decreased with increasing HDPE content. This reduction in impact strength can be attributed to the brittleness of the polymer matrix at higher ratios, resulting in lower energy absorption capacity. Overall, the results of this study indicate that the mechanical properties of natural fiber composites are strongly influenced by the polymer composition, specifically the ratio of HDPE in the composite. Balancing the amount of HDPE in the composite is crucial to achieving the desired mechanical properties for specific applications. This research provides valuable insights into optimizing the polymer composition of natural fiber composites to enhance their mechanical performance and expand their potential applications in various industries.

Thesis Overview

1.INTRODUCTION

Research and development of natural fibers as reinforcement for many different sectors is growing interest to scientists and engineers. Cellulosic fibers like henequen, sisal, coconut fiber, jute, palm, bamboo, wood, paper in their natural condition as well as, several waste cellulosic products such as shell flour, wood flour and pulp have been used as reinforcement agents of different thermosetting and thermoplastic resins (Ahlblad et al., 1994).

Fiber reinforced composites with thermoplastic matrices have successfully proven their high qualities in various fields of engineering application. However Natural fibers generally have poor mechanical properties compared with synthetic fibre but this composite were used as a source of energy to make shelters, clothes, construction of weapon (Benjamin and Tobias, 1990).

Since the beginning of human existence, people have developed plant fiber composites. Brahmakumar et al. (2005) reported that these composites were used for human purposes. The use of fibers as cloth was centered largely in the country side, with higher quality, textile being available in the towns. In late medieral Germany and Italy, fibers were employed  in cooked dishes, as fillers in pies and boiled soup.

A composite may be defined as a physical mixture of two or more different materials. The mixture has properties which are generally better than those of any of the material. It is necessary to use any one of materials to solve problem because acceptable cost or performance. These composites were produced in simple shapes and easy design structure by positioning the structure elements on top of each other to create the desired designs.

Natural fiber-reinforced composites have been increasingly utilized in quite widespread applications.

Natural fibers are obtained from different parts of the plants. For example hemp, jute, flax and sisal fibers are already used in automotive industry (Jacob et al., 2014).

In polymeric composite terms, natural fiber reinforcement is a manufacture assembly of long or short bundles of natural fibers to produce a flat sheet or mat of one or more layers of fibers. These layers are held together either by mechanical interlocking of the fibers themselves or with a binder to hold these materials together giving the assembling sufficient integrity to be handled. The un-reinforced plastics have low density are relatively easy to process, resistant to weathering and do not require a surface finish.

The components of natural fibers are cellulose, hemicelluloses, lignin, pectin, waxes and water soluble substances. The cellulose, hemicelluloses and lignin are the basic components of natural fibers, governing the physical properties of the fibers (Pelet et al., 2006). In order to fully utilize the natural fibers, understanding their properties vital. A unique characteristic of natural fibers is depended upon the variation in the characteristics and amount of these components, as well as difference in its cellular structure. Therefore, to use natural fibers to its best advantages and most effectively in automotive and industrial application, physical and mechanical properties of natural fibers must be considered. Many studies have investigated the properties of natural fibers. Numerous researchers have studied mechanical properties of varied natural fibers (Khalil and Rozman, 2007). However the fibers modification is required and needed to improve mechanical properties for composites products. Efficiency of the fiber-reinforced composites also depends on the manufacturing process that the ability to transfer stress from the matrix to fiber (Shibata and Fukumoto, 2005).