Manufacturing of three dimensional sandwich parts by direct thermoforming

Sandwich panels have been used extensively in the transportation industry. However, as geometric complexities increase, the manufacturing techniques r equire longer cycle times and significantly increased tabour. Press forming of initially flat thermoplastic sandwich panels is a new cost-effective wa y of obtaining a complex part in a one-step process. Nonetheless, the heter ogeneous nature of the sandwich panels requires accurate control of the pro cessing stage, and the complex geometry of the final part can lead to wrink ling of the faces and local collapse of the core during forming. Therefore, the potential for complex shape forming of thermoplastic sandwiches. based on a polyetherimide (PEI) foam core combined with PEI warp-knitted reinfor ced skins, has been investigated. An experimental approach associated with numerical simulations was used to define appropriate processing windows. Se lective heating of the face sheets and the foam core was achieved, and part s were successfully thermoformed. The developed materials and process have open up new perspectives for use within the transportation industry. (C) 20 01 Elsevier Science Ltd. All rights reserved.