Lightweight, High Performance Composites – How to Account for the Uncertainty in Composite Material Properties


Question: How can I account for the uncertainty in composite material properties?

Answer: You can perform a Stochastic Analysis.

I've quoted a description from Andrew Main's Use of Finite Element Analysis to Create Robust Composite Designs – Going Beyond First Ply Failure.

Stochastic analysis is not a method that was developed for composites but the large scope for variation in a composite structure makes it very interesting to use this technology.  At the most basic level the materials we use have higher variation in stiffness or strength than a metallic material.  This can be handled by using a pure statistical approach to calculate expected worst case values.  However we can compound this problem by considering variations in resin content and fibre angle.  By varying these values as random design changes it is possible to do repeated analyses and get a “cloud” or “anthill” of design responses which can represent the scatter we would expect to see in real life.  Figure 1 shows an example output from this type of analysis.  We can identify from this analysis areas of a design where there is a high sensitivity to variation which may cause problems.

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