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1 * Corresponding author: [email protected]
2
Introduction to Nanocomposites
Ritu Malik1, Vijay K. Tomer2*, Vandna Chaudhary3, Nirav Joshi4 and Surender Duhan1,2†
1Department of Physics, D.C.R. University of Science & Technology, Murthal (Sonepat) Haryana, India
2Department of Materials Science & Nanotechnology, D.C.R. University of Science & Technology, Murthal (Sonepat) Haryana, India
3Center of Excellence for Energy and Environment Studies, D.C.R. University of Science & Technology, Murthal (Sonepat) Haryana, India
4São Carlos Institute of Physics, University of São Paulo, São Carlos, São Paulo, Brazil
Abstract
Nanocomposite is a special class of material that has emerged as potential candidate to solve technological problems in the engineering domain since long. These materials started to capture the industrial attention with the introduction of their special class of polymeric-based composites. From that point forward, composite materials have turned out to be basic building materials and are outlined and made for different applications including car segments, sporting products, aviation parts, buyer merchandise, and in the marine and oil ventures. The growth in composite usage was attributed to the enhanced product performance and global competition for lightweight components. Interestingly, composite materials could possibly replace steel and aluminum, in fabricating industrial products with their better performance. This replacement of steel and aluminium components with composite materials can fabricate goods which are 60-80% and 20-50% of original weight, respectively. In current scenario, the composites are obviously materials of choice for almost every engineering application. In this chapter, a detailed discussion regarding the types, properties, processing, applications and advantages/disadvantages of composites has been presented in great depth and broadness.
Keywords: Composites, fillers, fibers, reinforcements, matrix
2.1 Composites: An Introduction
A composite material is obtained by merging two or more materials (wood, minerals, plastic co-polymers and/or metals alloys,) to give a unique blend of physico-chemical properties. The concept of composites was mimic from the Mother Nature. The naturally available, wood, is a composite material which is composed of cellulose fibers in a matrix of lignin which is also called as natural glue. Also, the shell of snails and oysters are also a composite material. Recently, the studies have revealed that the strength of spider’s web fibers is many-folds better than man-made processed fibers. The concept was also used in ancient civilizations wherein clay consisting of husks or straws was widely utilized to build houses that withstand for hundreds of years [1].
The composite consist of matrix materials (metals, plastics, or ceramics) which are formed by reinforcing materials (fibers, particulates, or whiskers) in a matrix resin (Figure 2.1(a)). The fibers can be of any dimension i.e. continuous, long, or short. The function of reinforcing material in a composite is to provide stiffness and mechanical strength, while matrix induces the rigidity and resistance to environmental effects [2]. The reinforcing materials can be of any type such as mat, short chopped fibers and a woven fabric. The style by which the fibers are fitted in the composites can induce different properties in the composite [3]. The composite materials composed of polymer matrix are easily processable and readily available and therefore widely used in various industries. In composite materials, the fiber acts as load carrier wherein its strength is most along the axis of the fiber. The fibers which are long and continuous can be aligned in the direction of the load thereby leading to the formation of composite with much enhanced properties than the pure matrix material. Figure 2.1(b) shows that the chopped fiber with continuous fibers shows better properties than short lengths fibers. Therefore, the targeted application together with the manufacturing method leads to the selection of the continuous fibers or long fibers (structural applications) and short fibers (nonstructural applications) [4]. The short fibers are needed in the process of injection and compression molding, whereas continuous fibers are required in the process of roll wrapping, pultrusion and filament winding.
2.2 Functions of Fibers and Matrix
A composite material consists of fiber and matrix material. A great estimation of the respective parts of these two components is highly necessary to estimate the composite behavior. The primary functions of the two components in a composite are:
1 a) The fibers in composite carries ~90% load.
2 b) They provide thermal stability, strength and stiffness in the composites.
3 c) Fibers are also responsible for the insulation and electrical conductivity in the composite.
4 d) The matrix material provides rigidity and shape to the composite materials by binding the fibers together and simultaneously transfers the load to the fibers.
5 e) The matrix acts as crack inhibitor by isolating the individual fibers.
6 f) The matrix is responsible for good surface finish.
7 g) The matrix protects reinforcing fibers against mechanical damage and chemical attack.
8 h) The failure of composite material directly depends upon the compatibility between the matrix material and the reinforcing fiber.
9 i) The matrix materials greatly influence the composite properties such as ductility, impact strength etc.
Figure 2.1 (a) Formation of a composite material using fibers and resin and (b) Continuous fiber and short fiber composites.
2.3 Classification of Composites
Composite materials are commonly classified according to matrix and fiber constituent as follows:
1 1. The matrix classes includes:(a) Organic Matrix Composites (OMCs):• Polymer Matrix Composites (PMCs)• Carbon matrix composites (carbon-carbon composites)(b) Metal Matrix Composites (MMCs)(c) Ceramic Matrix Composites (CMCs)
2 2. The fibers can be distributed under three categories:(a) Fiber Reinforced Composites: these are composed of fibers (discontinuous or continuous) embedded in matrix material. The properties of a discontinuous fiber composite vary with the fiber length.(b) Laminar Composites (e.g. sandwich structures): these are composed of layers of materials held together