Low energy electron beam curing for thick composite production

The need for high quality composite materials has led aerospace and defence companies to develop new curing processes using Electron Beam (EB) or X-rays. For industrial purposes, the maximum electron energy which can be used without inducing radioactive phenomena is 10 MeV; with such an energy it is possible to cure composite materials (density 1.6 x 103 kg/m3) with maximum thickness of 25-30 mm and curing times one-two orders of magnitude less than for autoclave processes. With X-rays the maximum curable composite thickness is about 200 mm, but curing times become comparable to those of autoclave processes. These technologies, developed for specific aerospace composite items, require high investment costs for the electron accelerator and for the radiation shielding containing the whole process area. For the production of large composite items, investments strongly affect the cost of the product (i.e. a 10 MeV, 10 kW electron accelerator requires a concrete shield with a thickness of about 2-3 m). An alternative is to cure a composite item during the winding phase with a low energy electron accelerator (less than 500 keV). Proel Tecnologie (a space R and D company, now a Division of LABEN S.p.A. of Finmeccanica Group) developed a cost-effective process suitable for a wide range of applications. In this paper, the process is described with its main advantages; some characteristics of composites obtained by such a process are presented. (author)