LAYER-BY-LAYER E-BEAM CURING OF FILAMENT-WOUND COMPOSITE-MATERIALS WITH LOW-ENERGY-ELECTRON BEAM ACCELERATORS

In recent years, both in Europe and in the USA, the most important aer ospace companies have significantly increased their interests on new c uring processes, based on the electron irradiation, for the manufactur ing of composite materials. The reason of these interests can be found in the potential advantages associated to the electron beam curing, b oth in terms of cost-effectiveness of the manufacturing process and of ''added value'' in the obtained products. Currently, the electron bea m curing associated to the filament winding manufacturing process has been applied to polymerize the composite after the completion of the w inding process, i.e., after the structure wound around the mandrel has reached its final thickness. In this approach, the polymerization of the product throughout all its thickness can only be achieved using hi gh energy electrons (> 5 MeV), in this case, the thickness to be penet rated is significant (some cm). X-rays generated by the interaction of an energetic electron beam (in the range of 10 MeV) with a target mad e of material with a high atomic number (ref. Aerospatiale process) ar e required. Proel Tecnologie, now a Division of Laben SpA (a Finmeccan ica Company), has proposed a totally new method for the electron beam curing of filament wound composites. This method uses a low energy (le ss than or equal to 500 KeV) electron beam to achieve the curing of th e product during the phase of deposition, around the mandrel of the re sin impregnated fibers. In this way the composite is polymerized and g rown layer-after-layer which the desired thickness is achieved. As the thickness of a single (or eventually few) layer(s) penetrated by the electron beam is of the order of some hundreds microns, the correspond ing electron energy can be in the range of hundreds of KeV. In the fra mework of the research and development activities carried out by Laben Proel Tecnologie Division on this new process (patented) called ''lay er by layer E-beam curing,'' new proprietary resin formulations, suita ble for the cationic polymerization mechanism, and composite sample ha ve been prepared and characterized. In the paper, both the technical a spects relevant to the layer by layer polymerization process with prop rietary formulations and the cost effectiveness advantages intrinsical ly associated to the new process are addressed and are discussed in de tail.