Estimation of Mechanical and Tribological Properties of Epoxy-Based Green Composites

Introduction

Composites constitutes of two main constituent materials: matrix and reinforcement. The matrix material surrounds and supports the reinforcement materials by maintaining their relative positions. The reinforcements impart their special mechanical and physical properties to enhance the matrix properties. A synergism produces material properties unavailable from the individual constituent materials, while the wide variety of matrix and strengthening materials allows the designer of the product or structure to choose an optimum combination. The reinforcing material can be of the form of particle (usually called filler) or fibre. In a particle reinforced composites, the reinforcement can be with large particle or small particle. It is not strictly the physical dimensions of the particles by which the materials are classified; rather it is the mechanism of reinforcement. In a small particle reinforced material the mechanism is on a molecular level whereas in case of large particle it is at macro level. The particles may be dispersed into or precipitated from the matrix; hence the properties can be varied with the amount and type of dispersion.

In the recent years, rising concern towards environmental problem and the need for more multifarious polymer-based materials has led to increasing interest about polymer composites reinforced with Green reinforcement, i.e., materials derived from natural resources like trees etc. The natural composites, or green composites, have shown a growth of interest because of their recyclability, biodegradability and abundant availability (Thakur et al., 2012).

Specific properties of natural composite such as light weight, low cost, renewable in nature, high specific strength and modulus have extended their usage and allow a considerable reduction in the use of non-biodegradable polymers and non-renewable resources (Bhowmick et al., 2012). Also in automobile industry the use of wood based natural composites enhance the mechanical strength and acoustic performance, reduce material weight and fuel consumption, improve biodegradability and production cost for the auto interior parts (Herrera-Franco and Valadez-González, 2004). They are also much less abrasive than inorganic-mineral counterparts to process machinery, less dangerous for the production employees in case of inhalation, easy to be scorched, and leads to final composites with lower specific weight (in comparison to mineral-filled counterparts) and allows obtaining interesting properties in terms of thermal and acoustic insulation. Also natural composite can be easily disposed at the end of their life cycle by compositing or by recovery of their calorific value in a furnace which is not possible in synthetic composite with reinforcement such as glass.

The woven banana fibre reinforced epoxy composites showed a very stable mechanical behaviour under different loading and speed condition (Sapuan et al., 2006). The epoxy based pissava fibres composite has rich silicon content on the surface and large dispersion in their mechanical properties (Nascimento et al., 2012). The flexural modulus of coconut fiber polypropylene matrix composite can be improved by using adequate fiber granulometry and extruder screw speed and that of agave fibre reinforced epoxy composite were significantly high due to alkali treatment of the fibre (Ishizaki et al., 2008; Mylsamy and Rajendran, 2011).

Almost all of the commonly available natural plant fibres are being used for reinforcement in combination with non-biodegradable matrix materials such as unsaturated polyester, epoxy resin, polyethylene and polypropylene (Ashori, 2008). Among these, epoxy resins are very versatile in nature. They are one of the most important classes of thermosetting polymers which are widely used as matrices for composite materials and as structural adhesives. They are amorphous, highly cross-linked polymers and this structure results in these materials possessing various desirable properties such as greater tensile strength and modulus, uncomplicated processing, fine thermal and chemical resistance, and dimensional stability (Song et al., 2000).