Confidence with composites

When they first arrived, composites were seen as an exciting step forward in materials technology because they could be tailored to meet performance requirements which were beyond the reach of conventional materials. They came at a price, but that was arguably not the most formidable barrier to their general use. Their great advantage, versatility, was also their greatest drawback. It is difficult for the busy engineer to come to grips with the diversity that give composites such a large window of properties and opportunities.

Now, researchers at the National Physical Laboratory (NPL), funded by the DTI, have developed a solution called CoDA. This is a software package capable of dealing with material anisotropy and structural form to help designers with preliminary design stages of engineering composites components. It integrates the generation of composite materials properties with structural element design, just like engineers do in practice.

Predictive models take the properties of the fibres and the matrix and predict the properties of the resulting composite. The use of correlation factors obtained during experimental validation ensures these predictions are realistic. This approach can also use knowledge of the properties of individual plies to predict the properties of laminates.

The properties can then be used in integrated design modules based on representative panel and beam components and sub-components for a broad range of geometries and loading conditions.

The engineer can immediately see the effect on the deflections of a panel or beam while changing any of the input data, eg fibre properties, matrix properties or laminate lay-up. Computer screening can weed out the doubtful materials and designs and therefore help save on development costs.

The software can be used for materials formed by all process routes from hand lay-up to injection moulding, including pultrusion, resin injection and autoclaved pre-pregs.