Shaping fibrous reinforcements in composites

he production of a part using composite materials differs significantly from that using more conventional materials such as metals or solid polymers. The final material and part geometry are often obtained simultaneously, and the properties and qualities of the final composite structure depend on both the components (fibers and matrix) and the way in which they have been processed. Composite manufacturing processes are generally of the forming type. They are specific in that they use the absence of matrix (or its uncured state) to allow deformations of continuous reinforcements made possible by their fibrous nature.

As a result, these particular mechanisms, which are based on the mechanics of fibrous media, usually woven, require specific analyses and models, and in particular the development of shaping simulation tools specific to composite materials.

In this article, after describing the specifics of composite forming, we analyze the various deformation modes and mechanical behavior of a woven reinforcement. In particular, biaxial tension and planar shear tests are described. The final section deals with the simulation of fiber reinforcement forming (draping or preforming) and presents :

• the net method, based on highly simplifying assumptions;

• the use, within the framework of the finite element method, of approaches specific to woven fabrics, which take into account the mechanical behavior of the reinforcement and the stress boundary conditions.