Use of composite materials in mass production Essay Example

COMPOSITE MATERIALS 11

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USE OF COMPOSITE MATERIALS IN MASS PRODUCTION

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Abstract

Composite materials are rapidly expanding the horizon of material scientists and product designers in all engineering disciplines. The optimization process achieved in the manufacture of these materials is literally freeing the designer from the constraints related to the manufacture and selection of convectional natural materials. For instance, it is difficult to find a tough, strong and yet lighter material. Generally a composite material consists of a reinforcement fibre material and matrix media that binds the former.

Contents

Abstract 2

Introduction 4

How composites are made 6

Reinforcement Fibers 7

The scope of reinforcing in composite material 7

Function of the matrix 8

Moulding Methods 9

Tooling 9

Application of Composite Materials 9

Conclusion 10

References 11

Introduction

Composite materials refers to composition materials either naturally occurring or engineered materials comprising of one or more constituent dissimilar materials with varying physical and chemical properties that remain distinct and separate at either microscopic or macroscopic scale within the structure of the final material (Bullen, 2010). An example of commonly used composite material is the brake pads in automobiles, which are a composite of hard ceramic rooted in a metal matrix, bathtubs and toilet bawls are made of cultured marble with granite. According to (Pop, 2010), composites are widely used in more demanding fields such as aero plane and spacecraft manufacture. Concrete is also classified as a composite and it is widely applied as an engineering material more than any other naturally occurring material.

Composite materials are rapidly expanding the horizon of material scientists and product designers in all engineering disciplines. These products are offering quite exiting radical solutions to the difficult engineering scenarios and problems. The materials are being produced in formats that all better use of their high merit while reducing to some extent the undesirable deficiencies associated with natural materials (Strong, 2008). This optimization process is literally freeing the designer from the constraints related to the manufacture and selection of convectional natural materials. For instance, it is difficult to find a tough, strong and yet lighter material. However with composites such tailor – made materials can be produced such allowing the designer to come up with entire rethinking of a design technical hitch and thus offering cheaper and superior engineering solutions (Rufe, 2002).

The concept of ‘composite’ is not an invention of man. Wood is a natural composite that is composed of cellulose fibers amalgamated in lignin matrix. Wood is composed of cellulose reinforcement fibres – for material stiffness and strength, in a resin matrix of lignin. The earliest known artificial composite material may have been the building blocks that were used by Egyptian in the construction industry. (Rufe, 2002) The bricks were made up of straw and mud.

Advantages of composite materials over metal materials are:

  • Low weight per unit volume

  • High specific strength and stiffness indices

  • Flexible mould ability into intricate shapes

  • Low thermal expansion coefficient and electrical conductivity

  • Improved toughness and resistance to fatigue

  • Reduced radar visibility- especially in making military hardware

However, these materials do have some drawbacks and limitations as follows;

  • High production cost and hence end product

  • Difficulty in product manufacturing

  • Difficulty in joining and fastening

  • Solvent, heat and moisture attack

  • Susceptibility to hidden damage risks

How composites are made

Generally composite materials comprises of two categories of material; reinforcement material and matrix material. In the final composite material, the matrix material surrounds the reinforcement thus maintain their relative structure position. The reinforcement material introduces their superior physical and mechanical properties thus enhancing the quality of the final constituent composite material (Morey, 2009). The synergism releases superior material quality and properties that were previously absent in the individual ingredient materials. This increased variety of matrix and the resulting strengthening allows a product designer to choose optimum possible blend and combination (Strong, 2008).

Basically composites are formed from their constituent element material through a moulding process. The matrix material can be introduced to the reinforcement material prior or after placement into the mould cavity or moulding surface. The matrix material undergoes a melding process before finally setting to the desired shape and structure. A typical melding process is polymerization process used in making polymer materials (Morey, 2009).

There are a variety of moulding processes and the choice of any of the them depends on the following; design requirements of the final product material, the selected matrix and reinforcement material, and finally the gross quantity of the material to be involved in making the composite (Morey, 2009). Larger composite quantities can make rapid and automated production and melding procedures to be economically viable. Needless to say, lower material quantities demands reduced capital investment but include higher labour and tooling expenses.

Resin solutions are most widely used polymer matrix material in most commercially manufactured composite material. However there are numerous polymer materials based on the initial basic ingredients (Rufe, 2002). The most widely known polymers include, Vinyl ester, epoxy, polyester, polypropylene, and others. In majority of this composite material, ground minerals are the commonly used reinforcement materials.

Reinforcement Fibers

These materials offer the expected superior mechanical and physical qualities of the final composite material. These fiber reinforced material can be divided into two categories i.e. continuous fiber material, and short discontinuous materials. Continuous materials often comprise of either laminated or layered structure (Pop, Ungur, & Lopez- Martinez, 2008). They are available as dry, pre-impregnated in desired matrix (resin) or, in single unidirectional tapes of different lengths, width, shapes, and so on. Most continuous fibres are expensive initial composite materials (Kaw, 2005).

Short and discontinuous fibres are often applied in situation where the composite will undergo sheet molding or compression molding during the melding process. These short fibres often appear in form of flakes, chips, and ply laminate of random shape. These short ‘prepreg’ sheets comprises of single laminate layers of fibres which are impregnated with the desired resin and flattened between the paper carrier sheets (Strong, 2008).

Use of composite materials in mass production

Source: (Strong, 2008)

The scope of reinforcing in composite material

It is worth noting that, composite materials are expected to satisfy the desired main purpose of designing the products, majority of which are crucial in the performance of the final material. Bundles of reinforcing fibres add little value to the material engineer, and it is only the use of matrix that enables the material engineer to make the fibres into a useful form. The role of these particulate fiber elements and the reinforcing matrix are different, however they are interdependent. In the composite material the fibre retains the composite particulate matter mass in a solid form mass. The matrix or binder performs a variety of functions which can be well understood in analyzing the proper composition action and hence the physical and mechanical properties of the composite material (Pop etal, 2008).

Function of the matrix

  • The matrix acts as a binder joining the particulate fibres together, keeping them in position against the stressed forces directions. When a composite is loaded, the forces are transferred to the fibres- the chief load-bearing segment. However, it is the matrix that ensures that the composite withstands such loads be it compression, shear of flexural loads. The matrix therefore acts as a load transfer medium, and therefore the load transfer efficiency is a factor of quality of the bond between the matrix and fibre material (Morey, 2009).

  • The binder or matrix separates the individual fibres thus enabling them to act as separate independent entities. Most of the fibre material are possesses variable strength levels and are often brittle solids. Matrix material helps to keep them apart thus avoiding them from failing catastrophically. If a crack develops, the matrix helps to control it from spreading though the fibre sequences in direct contact (Kaw, 2005)t.

  • The matrix material should provide protection to the fibre material against physical damage such as surface abrasion and adverse weather attack. For instance, matrices used in glass fibres allow for diffusion of water.

  • Matrices used in ductile material show offer the necessary means of stopping cracks that emanates from broken edges.

Moulding Methods

Ideally in making composite materials, the matrix and reinforcing fibres are combined, pressed, processes to go through a melding process. In thermosetic polymer matrix, this process is a curing reaction which is set off by application of heat or through a chemical activity. In a thermoplastic matrix, the melding process is represented as solidification processes from the molten state. The various moulding type include; autoclave moulding vacuum bag moulding, resin transfer moulding (Strong, 2008).

Tooling

A number to tool materials are used in the manufacture of composite materials and structures. These include aluminum, reinforced silicon, rubber, carbon fiber and so on. (Kaw, 2005) The choice of materials depends on:

  • Expected cycles of tool use

  • End product surface finish and tolerance

  • Coefficient of thermal expansion of the composite material machined

  • Curing method used

  • Moulding method and matrix material uses

  • And cost consideration of the machining process

Application of Composite Materials

Concrete is generally the widely used artificial composite material. Basically concrete is composed of loge aggregate material which is held together by cement binder or matrix material. Concrete does not withstand tensile loading, thus metal bars are often added into it to boost its resistance and hence reinforced concrete (Bullen, 2010).

Fibre reinforced composite materials, although costly to produce, have gained reputation in aerospace industry due to their high performance and light weight. They are now widely used in the manufacture of tails, propellers, fuselages and making racing cares in high performance automobile racing cars. Due to its superior heat resistance characteristics, carbon composites material have been used in the manufacture of military armored vehicles and space craft entry vehicles (Morey, 2009).

Graphite reinforced fibers are applying in situations where high thermal conductivity and high strength is required. The material also possesses good abrasion qualities that metal elements (Strong, 2008).

Conclusion

This technical paper has presented the various types, production method and applications of composite materials. The choice and selection of type of material is given by final products required, quantity to be produced, applications and eventual cost of production.

References

Bullen. (2010, March 3). “Unified Composite Structures”. Manufacturing Engineering Magazine, SME Editor, pp. 47-55.

Kaw, A. K. (2005). Mechanics of Composite Materials . CRC: Woodhead Publishing.

MOREY, B. (2009, March 3). “Innovation Drives Composite Production”. Manufacturing Engineering Magazine, Society of Manufacturing Engineer Editor, pp. 49-60.

POP, P. A., UNGUR, P., & LOPEZ-MARTINEZ, L. (2008). C.:”Rheological Aspects to Horizontal Rotational Forming of Thermoplastic Materials”. ASME Conference MSEC & ICMP2008 (pp. 1-7). Evanston, IL, USA: Proceedings of MSEC2008/ICMP2008.

POP, P., & BEJINARU, P. (2010). Manufacturing process and applications of composite materials. Fascicle of Management and Technological Engineering, Volume IX (XIX),, 2-4.

RUFE, P. (2002). Fundamentals of Manufacturing. Dearborn, MI, USA,: Society of Manufacturing Engineer Editor,.

STRONG, A. (2008). Fundamentals of Composite Manufacturing. Materials, Methods and Applications. Dearborn, MI, USA: SME Editor.