Search

Environmental ageing in composites is a very important issue for the effect induced on material properties. The most common effect is induced by absorption of low molecular weight substances (water or organic solvents), usually controlled by diffusion mechanisms. Some cases of use of hybrid materials, coupling low diffusion plies with "conventional" ones are discussed and potential improvement of composites for structural applications based on such concept is envisaged. Specifically, metal hybrid composites (GLARE), multilayer amorphous-semicrystalline materials and composites modified with layer of nanocharges or nano-reinforcements are considered, and the absorption kinetics are evaluated by a numerical model.

Cooling rate of semicrystalline thermoplastic (PEEK) based composite parts has been assessed by means of a thermal flow model. Cold tool thermoforming was found suitable for thin parts, but the use of a preheated tool is suggested. Cooling rate is critical for automated lay‐up; consequently the optimization of this technique requires the use of a complex apparatus, able to provide both heating of the part during lay‐up and a control of the cooling rate. Alternatively a modified cooling rate vs. crystallinity behavior of the material must be achieved.