expansion of composite usage assisted with the advancement in the low-cost production techniques has helped in decreasing the cost of fibers from $150.00/lb (year 1970) to about $8.00/lb (year 2000). The composites utilization in important industries are discussed below:
2.9.1 The Aerospace Industry
This is the first industry to realize the benefits of composite materials. Glass, carbon, and Kevlar fiber composites are frequently used in designing aerospace parts for airplanes, rockets, and missiles, which all fly higher, faster, and farther with the help of composites. The fin boxes, flaps, horizontal/vertical stabilizers, wing skins and other structural components are being designed with the composites which help in lowering down the weight of the structure [14]. A mass reduction of 20 to 35% can be achieved using composite materials. This weight saving in fighter planes enhances the payload efficiency as well as the missile range. In spacecrafts, the composites help in reducing its weight which assists in maintaining the dimensional stability in low earth orbit, where temperature variate in the range from -100 to +100 °C. Carbon epoxy composite laminates provides zero coefficient of thermal expansion in space structures including tubular truss structures, facesheets for the payload baydoor, antenna reflectors, etc.
2.9.2 The Automotive Industry
Composite materials are used in automotives for their excellent surface finish, styling details, and processing options. Composite materials have been used successfully in the design of small/medium/heavy truck applications and passenger/sports cars due to the tough cost concerns in the automotive market. Such composites mainly uses glass fibers as reinforcements rather than carbon fiber composites due to their higher costs.
2.9.3 The Sporting Goods Industry
In the sports and recreation equipment industries, the structural composite are used in manufacturing racing boats, high-performance sporting tools and other sporting products such as golf shafts, fishing rods, snow skis, tennis rackets, etc. Being manufacturing by composite materials, these products are lighter in handling and gives more comfort to the player and thus deliver good performance.
2.9.4 Marine Applications
Owing to their light weight and corrosion resistance properties, the composite materials are widely used in fabricating marine products e.g. buoys, power boats, passenger ferries, etc. This not only enhances the fuel efficiency but also increases the speed and portability. The glass-reinforced plastics (GRP) with foam and honeycomb as core material constitute about 70% of all recreational boats and off shore pipelines for oil and gas extractions. The GRP material reduces the installation and control costs and simultaneously provides better corrosion resistance and mechanical performance.
2.9.5 Consumer Goods
The composite are used in developing a variety of consumer goods doors, including chairs, computers, printers, sewing machines, tables and bathtubs. The components of these products consists of short fiber composites prepared by using compression molding or injection molding.
2.9.6 Construction and Civil Structures
The composites are mostly utilized in construction and civil industries. The carbon- and glass- reinforced plastics in bridges provides improved corrosion and durability to the structure. This saves a significant amount of time in repairing and installing which is results in minimizing the blockage of traffic. Besides, the columns can be wrapped by aramid/epoxy, carbon/epoxy, and glass/epoxy in creating earthquake proof structures.
2.9.7 Industrial Applications
The composite materials are quickly finding usage in various industrial applications. Composites with the help of filament winding techniques can be used in developing industrial drive shafts for cooling-tower applications and industrial rollers and shafts for the printing industry. Short fiber composites processed using injection molding techniques are used in pistons, pump/roller bearings and bushings. Composites are also used for making robot arms and provide improved stiffness, damping, and response time.
2.10 Special Features of Composites
Composites are generally utilized in applications which demands for light weight and high performance. Following are their advantages over traditional materials:
1 1. Composite materials possesses the part integration capabilities which otherwise not possible in metallic counterparts which can be replaced by a single composite component.
2 2. Composite materials exhibit high specific stiffness due to which they are almost one fifth and one half lighter than the weight of steel and aluminum, respectively.
3 3. Composite structures can act as “smart” materials wherein the embedded sensors can monitor the online processes. Such smart composites are generally used to monitor fatigue damage in aircraft structures.
4 4. The composite material possess high specific strength (strength-to-density ratio), which enables the airplanes and automobiles to move faster and with better fuel efficiency.
5 5. Composite materials offer many options of design flexibility and good dimensional stability due to its lower coefficient of thermal expansion (CTE) than metals. For example, the CTE of composites can tuned to zero by selecting suitable materials and lay-up sequence.
6 6. Unlike metals (iron or aluminium), the composites offer high corrosion resistance and does not require special coatings or alloying.
7 7. The composite materials also exhibit high fatigue strength (endurance limit) e.g. the unidirectional carbon/epoxy composite possesses a fatigue strength of ~90% whereas the steel and aluminum alloys fatigue strength only up to ~50% of their static strength.
8 8. Composite materials can easily produce net-shape components thereby eliminating several machining operations and reducing the process cycle time and cost.
9 9. Composite materials can also be utilized in the facile fabrication of complex parts which does not require process of welding or riveting separate pieces, as needed for metals.
10 10. Composite materials can be easily manufactured and assembled which not only minimizes the number of parts in a product but also reduces the assembly and joining time. This in-turn reduces the overall cost.
11 11. Glass-reinforced and aramid-reinforced phenolic composites are utilized in designing aircraft interior panels due to their low smoke and toxicity.
12 12. Composite materials reduce the vibrations to one order of magnitude better than metals and so utilized in airplane and golf clubs.
13 13. By changing the fiber orientation, fiber type, and/or resin systems, the design of the composites can be easily tailored.
14 14. The processing cost of tooling in composites is much lower than that for metals because of lower pressure and temperature requirements.
2.11 Composites vs Metals
With the similar properties, there is always a choice between metals and reinforced composites. So, a comparison of main characteristics of both is made here:
1 1. Composites are much lighter than metals. Generally, composites based structures, due to their low density, are 25-45% lighter than
