Forming of Composites

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Many modern structures, including primary aerospace structures, high performance sporting goods, and marine and wind turbine structures, are progressively coming to rely on advanced composite materials based on fiber-reinforced thermoset and thermoplastic polymers. Conventional composite manufacturing techniques, such as hand lay-up, are labor-intensive, time consuming, and costly. Increased demand on composite parts, together with an increase in their size and complexity, puts a strain on traditional processing methods and drives the need for fast, adaptive, and cost-effective manufacturing alternatives. The low manufacturing times and costs associated with automated manufacturing processes such as Automated Tape Laying (ATL) and Automated Fiber Placement (AFP) offer great promise to meet the growing need for composite materials in the aerospace and automotive industries. The limiting factor for the viability of these automated processes is their capacity to produce complex geometries. To improve productivity while maintaining the geometrical complexity of components, a three-step process is undertaken. First, flat laminates are laid down by automated machines or hand layup. Then these laminates are subjected to a forming process. This forming step involves the application of heat and pressure to transform flat laminates into the desired shape prior to curing. Finally, the formed parts are cured. To ensure successful composite forming, the mechanisms that cause defects such as wrinkling must be thoroughly understood. The success of composite forming is determined by selection of proper processing conditions which control the material properties and prevent any in-plane and out-of-plane wrinkling.