Microstructure and mechanical properties of epoxy – rice husk ash composite

Project Abstract

<p> </p><p>This study is about the production and characterization of epoxy-rice husk<br>ash composite. Composites were produced at 10%,20%,30%,40% and 50%<br>volume fraction of Rice Husk Ash(RHA) fillers and the epoxy was cast neat at<br>0%RHA which served as the control .The microstructure of the composites were<br>studied with Scanning Electron Microscopy(SEM) and Energy Dispersive X-ray<br>Spectroscopy(EDX).Mechanical properties of the composites such as tensile<br>properties(tensile stress, tensile strain, Young’s modulus, tensile strength and<br>percentage elongation at fracture),compressive strength, toughness, flexural<br>strength and hardness were experimentally determined in the engineering<br>labouratory using hounsfield (monsanto) tensometer, charpy v-notch impact<br>testing machine, flexural testing machine and Rockwell hardness testing machine.<br>The Scanning Electron Microscopy (SEM) analysis showed that interfacial<br>interactions existed between the rice husk ash particles and the epoxy matrix.<br>Energy Dispersive X-ray Spectroscopy (EDX) analysis indicated that interfacial<br>reactions existed between the epoxy matrix and the rice husk ash particles<br>because the composites did not contain homogenous elements. However each of<br>the composites contained C,O,Si and Cl while the cast neat epoxy(control)<br>contained C,O and Cl. Results of the mechanical property tests showed low gain<br>in hardness, toughness, flexural strength and Young’s modulus. The tensile<br>properties showed that at 40%RHA the highest tensile strength of 37.006MPa was<br>obtained, the cast neat epoxy (control 0%RHA) had the best Young’s modulus of<br>356.538MPa and percentage elongation at fracture improved from 1.3% to 2.0%<br>as volume fraction of rice husk ash increased from 0% to 10%,20%,30%,40% and<br>50%.Increasing the volume fraction of rice husk ash from 0% to 10%,<br>20%,30%,40% and 50% led to decrease of these mechanical properties toughness<br>from 2.0J to 0.3J,hardness from 344hardness value to 144 hardness value and<br>flexural strength from 6.0Mpa to 1.50Mpa.There was significant improvement in<br>the compressive strength of the composites from 15.75MPa to 18.75MPa as the<br>volume fraction of rice husk ash increased from 0% to 10%,20%,30%,40% and<br>50%.It was deduced from the study that epoxy-rice husk ash composite is<br>suitable for engineering applications subjected to compression. Surface coating of<br>rice husk ash could be used to improve its adhesion to the epoxy matrix in order<br>to enhance the mechanical properties of the composites for other engineering<br>applications.</p><p>&nbsp;</p> <br><p></p>

Project Overview

<p> INTRODUCTION<br>1.1 Background Information<br>Most times engineers are faced with the task of developing a new material that<br>has light weight, low cost and good mechanical properties. A promising option to<br>this task is to use a low density particulate material like rice husk ash in a polymer<br>matrix to form a polymer composite. Rice husk ash is a by-product of combustion<br>of rice husk at rice mills (Zemke and Woods, 2008). Researchers are currently<br>investigating the use of ash for composite production since ash is an abundant<br>agricultural waste, is renewable and has low bulk density. Rice husk ash had<br>been applied in other areas like manufacturing insulating powder, production of<br>refractory bricks, cement production and sandcrete block production. However<br>there are limited applications of rice husk ash in composite production.<br>A composite material is a microscopic or macroscopic combination of two<br>or more distinct materials with a recognizable interface between them. In a<br>composite material the constituents do not dissolve or merge completely in one<br>another. Normally the components in a composite material can be physically<br>identified and they exhibit interface between one another. A particulate composite<br>consists of a matrix reinforced with a dispersed phase in form of particles. Soft<br>particles like coir dust, rice husk flour, baggase ash, sawdust and rice husk ash can<br>be dispersed in a harder matrix to improve machinability and reduce coefficient of<br>friction (Lake,2002;Jiquao et al, 2010)<br>1<br>2<br>One advantage of a composite is that two or more materials could be combined to<br>take advantage of the good characteristics of each of them.<br>Composites are gaining a wide range of applications in engineering because of the<br>following advantages: weight savings, corrosion resistance, easy manufacturing,<br>low temperature processing, possibility of producing novel shapes, reduced parts<br>and long fatigue life (Nowosielki et al, 2006;Ranganathatiah,2010).<br>Composites can be made of two or more components, the matrix and the<br>dispersed phase. The properties of a composite material depend on the following :<br>properties of the matrix; properties and distribution of reinforcement, nature of<br>bonding at the interface and volume fractions occupied by the constituents (Lake,<br>2002).<br>A matrix is a material in which the reinforcements or other components of a<br>composite system are embedded. It can be made of metal, ceramic or polymer<br>(Askeland, 1994). The purpose of the matrix is to bind the reinforcements together<br>by virtue of its cohesive and adhesive characteristics, to transfer load to and<br>between the reinforcements and to protect the reinforcements from environment<br>and handling. The matrix is often the weak link in a composite when viewed from<br>a structural perspective. Chemical treatment of reinforcement materials or filler<br>increase interfacial adhesion between the matrix and fillers leading to better<br>mechanical properties of the composites (Gauthier et al, 1998). It is in view of<br>these expected roles of matrix materials that epoxy resin was used in this study.<br>3<br>A polymer matrix composite is a composite formed by the combination of a<br>polymer (resin) matrix and a fibrous reinforcing phase (Ezuanmustapha et al,<br>2005). Polymer composites are gaining importance as substitute for metals in<br>applications in the aerospace, automotive, marine, sporting goods and electronics<br>industries due to their light weight and corrosion resistance. Polymer matrix can<br>be classified as thermoplastics and thermo set. Thermoplastics include low density<br>polyethylene, high density polyethylene, nylon, polypropylene and polyester while<br>epoxy resin is an example of a thermo set.<br>Epoxy resin is currently of much research interest due to its superior properties<br>over polyester resin. Some of the properties of the epoxy resin identified by<br>researchers are low cure shrinkage, better resistance to moisture, better<br>mechanical properties, processing flexibility and better handling.<br>Epoxy resins are presently used more than all other matrices in advanced<br>composite materials for structural applications in the United States of<br>America(USA) Air Force and Navy. The dispersed phase of a composite refers to<br>the reinforcement or fillers added in the matrix and the role of reinforcement in<br>a composite material is to increase the mechanical properties of the neat resin<br>system (Askeland, 1994).<br>Filler materials are generally the inert materials which are used in composite<br>materials to reduce cost, absorb thermal stresses, improve mechanical properties<br>to some extent and in some cases to improve processing (Singla and Chawla,<br>2010). Fillers which increase bulk volume and hence reduce cost are known as<br>4<br>extender fillers while those that improve mechanical properties particularly tensile<br>strength are termed reinforcing fillers (Igwe and Onuegbu, 2010).<br>Many researchers like Suwanprateeb and Hathapamit(2002), Zemke and<br>Woods(2009) are optimistic to find out whether rice husk ash is a reinforcing<br>filler or an extender filler. The current challenge is to make composite production<br>cost effective and this has resulted to high filler loadings. An interface is the<br>boundary between the individual, physically distinguishable constituents of a<br>composite. It is the bonding surface or zone where discontinuity occurs. Interface<br>must be large and exhibit strong adhesion between the fibers and the matrix.<br>Wetting occurs at the interface and its failure at the interface is called debonding<br>which may or may not be desirable. Interfacial bonding is a bonding type in<br>which the surfaces of two bodies in contact with one another are held together by<br>intermolecular forces like covalent, ionic, vanderwaals and hydrogen bonds.<br>Interfaces have been identified as zones where compositional, structural and<br>mechanical properties are altered in composites. Mechanical properties are<br>properties of a material that are associated with elastic and inelastic reaction when<br>force is applied or the properties involving relationship between stress and<br>strain(Royalance, 2008).<br>Microstructure is the microscopic description of individual constituents of<br>a material. Microstructure studies of composites show what happens at the atomic<br>and microscopic levels of the interface.<br>5<br>Electron microscopy analysis is used to characterize the microstructure of<br>composites. Scanning electron microscopy shows the morphology and topography<br>of the composites while compositional analysis is conducted using energy<br>dispersive x-ray spectroscopy. Energy dispersive x-ray spectroscopy is a chemical<br>microanalytical technique used in conjunction with scanning electron microscopy<br>to determine the elements in the microstructure of a material.<br>1.2 Statement of the Problem<br>Most developing countries like Nigeria are not yet properly utilizing<br>agricultural wastes such as rice husk ash for gainful engineering production. Rice<br>husk ash constitutes environmental pollution and causes health hazards like<br>silicosis, cancer, tuberculosis, chronic cough and sight disorder in areas where it is<br>dumped. Therefore there is need to develop more ways of reducing the amount of<br>the waste in the environment. One of the easiest ways of solving the problem is to<br>rice husk ash as filler in epoxy matrix to form epoxy-rice husk ash composite.<br>Epoxy based composites can be used in producing sole of shoes, side stools ,slabs,<br>industrial flooring and other components for electrical and industrial engineering.<br>Material engineers are facing the problem of developing materials that have<br>low cost, light weight and enhanced mechanical properties for executing<br>construction works. Metals which have good strength are insidiously affected by<br>corrosion and heavy weight making the search for alternative materials like epoxy<br>based composites that can be substituted for metals in some engineering<br>6<br>applications inevitable. Particle filled composites are gaining wide research<br>interest due to the problem of delamination and fiber pullout associated with<br>fibrous composites. The behavior of epoxy resins have not been fully understood<br>by researchers especially its slow curing character. Microstructural study of the<br>effect of interfacial adhesions between particle and matrix is fundamental in<br>understanding mechanical behavior of polymer composites.<br>1.3 Objectives of the Study<br>The general objective of this project is to characterize composite materials<br>produced from different compositions of epoxy and rice husk ash. The specific<br>objectives of the study are:<br>1. To produce epoxy-rice husk ash composite using rice husk ash considered as<br>an agricultural waste as a filler.<br>2. To conduct scanning electron microscopy and energy dispersive x-ray<br>spectroscopy analysis on epoxy –rice husk ash composite and study the<br>effect of variation of rice husk ash volume fractions on the microstructure.<br>3. To carry out scanning electron microscopy on Adani Rice husk ash.<br>4. To examine the effect of rice husk ash volume fraction on some mechanical<br>properties of epoxy- rice husk ash composite and ascertain the suitability of<br>the composite for engineering applications.<br>1.4 Justification of the Study<br>7<br>This study is valuable in understanding the potentials of rice husk ash as<br>filler in composite production and the behavior of Epoxy resins. The study is<br>useful to engineers and researchers in the composite industry because it will help<br>to suggest ways of improving the mechanical properties of the epoxy-rice husk ash<br>composite. Composite production can offer employment opportunity to<br>unemployed youths due to low energy and machinery requirements for<br>production. The knowledge of microstructure and mechanical properties of<br>particle filled composites is vital in describing the behaviours at the interface and<br>the effect of forces on the composites. Proper understanding of the microstructure<br>and mechanical properties of composites will help to ascertain the engineering<br>application of composite in structures, industries, electronics, oil and gas, and<br>other industrial production.<br>1.5 Scope and Limitations of the Study<br>Experimental approach was used in this study involving composite<br>production, microstructural analysis using scanning electron microscopy and<br>energy dispersive x-ray spectroscopy as well as the determination of the<br>mechanical properties of the composite material. The composites were produced at<br>0%, 10%, 20%, 30% 40% and 50% volume fraction of rice husk ash fillers. The<br>rice husk used in the study was sourced from Adani rice mill, Enugu State,<br>Nigeria. Apart from production of the amorphous rice husk ash at 550oC all other<br>experiments were done at room temperature. In order to adequately view the<br>8<br>particle and matrix interfacial interactions two magnifications of 200x and 2000x<br>were used for the scanning electron microscopy analysis. Lack of accessibility to<br>transmission electron microscope hindered possibility of investigating other<br>microstructural features. Other limitations faced in the research were sourcing the<br>epoxy resin and getting the characterization equipment <br></p>