Strength and Stiffness Advantages

One of the most common ways of expressing the effectiveness of strength or stiffness of a material is as a ratio of either of the quantities to the density, i.e., weight per unit volume. Such an index does not include the cost to achieve a certain strength or stiffness, but cost comparisons are probably not valid by themselves because many factors influence cost beyond raw material cost. 

Not all of the strength and stiffness advantages of fiber-reinforced composite materials can be transformed directly into structural advantages. Prominent among the reasons for this statement is the fact that the joints for members made of composite materials are typically more bulky than those for metal parts. These relative inefficiencies are being studied because they obviously affect the cost trade-offs for application of composite materials. Other limitations will be discussed subsequently. 

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