An Introduction to the Concept of Distortion and Shrinkage in Composites

High performance composites usually consist of continuous fibers and a thermoset matrix. A well-known example is carbon fiber/epoxy composites. When this kind of material is cured، residual stresses and/or shape distortions are produced owing to thermally and chemically induced volumetric strains. The cure implies a stage where a thermoset matrix is transformed from a liquid to a solid state. It is a quite complex thermo-mechanochemical process that in addition to volumetric strains، involves heat generation and dramatic changes in mechanical properties. For manufacturing of parts with high shape tolerances، such as aircraft components، the geometry of the mould is compensated to accommodate for shape distortions. Today، this is based on thumb rules and tests are followed by trials، which are time consuming and expensive. Development of a tool for prediction of shape distortions and residual stresses is therefore an important step toward more optimized processes for manufacturing of composites. In this paper، we examine the factors affecting distortion and thermal contraction in each application. These guidelines are considered useful to reduce shrinkage and thermal distortion.