Composites can be used for a variety of reasons. 9 out of 10 successful composite products combine the multiple benefits of composite materials to reach the desired function(s). For example:
- Naval architecture: Lightweight + corrosion resistance
- Radomes: Radar transparancy + freedom of shape + lightweight
- Architecture: Thermal insulation + aesthetics/freedom of shape + lightweight
The reasons for choosing composite are listed below. While the characteristics may prove advantageous in some projects, they may be a disadvantage in others.
Steel structures typically require periodic maintenance such as conservation and paint systems to prevent corrosion. Composites are not susceptible to corrosion resulting in lower Life-cycle costs.
In general, fiber reinforced plastics outperform metals (e.g. steel and aluminium) in strength.
Composite materials are resistant to a lot of chemical products such as acids, hydroxides, crude oil, etc. Corrosion resistance against salt and seawater is excellent.
High stiffness to weight ratio
The stiffness to weight ratio of a high modulus carbon fiber construction is typically 5 times higher than steel or aluminium.
Though composite materials themselves are slightly more expensive than metals, combining properties such as insulation and weight savings often results in a cost effective product.
Freedom of geometry
Double curved shapes are easily produced in composite materials at almost no extra cost. For production of limited series the relatively low moulding costs are an additional benefit.
The specific weight of composites varies between 1.5 and 2.0 compared to 2.7 to 7.8 for aluminium and steel.
Slender constructions and seamless façades are examples of aesthetics driven design. These type of structures are impossible to construct with traditional materials.
Limited thermal expansion
Thermal expansion of composite materials can be tuned. Depending on the fiber used it can vary between 0 and 30 where steel has an alpha of 12.
Integration of functions
By combining functions such as strength and insulation in one product, a composite solution is often more cost effective than the sum of traditional solutions.
Typical GRP lambda values are 1, compared to 50 for steel and 237 for aluminium, which results in excellent insulation properties.
Composites are very well known for their transparency to radar and low damping properties.
The non-magnetic properties of glassfiber reinforced composites are a major advantage especially in sonar and radar applications.
The fatigue resistance of composites is much better than that of metals. Of course fatigue failure also occurs in GRP and CFRP and has to be analysed in detail.