Material Selection

Composite materials possess many properties that differ significantly from those of conventional metallic materials such as steel and aluminium and as a result require design and analysis methods tailored to their unique characteristics. Composites materials are a rapidly developing technology and in order for a designer to make a well-reasoned choice of material for any given component or product, a range of candidate composite materials must be evaluated, characterized and confirmed as appropriate for use in the application.

In many scenarios, the composite will be composed of various layers (plies) of different materials in different orientations which require detailed analysis techniques to cope with the complex calculations involved in analyzing the lay-up on a ply-by-ply basis. Properties of the individual composite plies can be affected by many factors including the fibre type, matrix type, percentages of constituent materials, cure process and environmental conditioning. Determining the level of reliable working properties and "allowables" is prerequisite for any quality analysis.

Low cost composite solutions now utilize random chopped or random continuous materials in their construction. The chopped material is often robotically sprayed or placed to create a dry preform which gives the added advantage of being able to work easily and quickly with variable thickness material. Properties for this type of material can in some processes be tuned to give biased properties in different directions with local material content.

Early in the design, composite materials properties can be drawn from a reputable database or manufacturer’s datasheets. However, as the design develops the materials should be tested in conditions close to the manufacturing process that is going to be employed in the final component.