Rapid-prototyping resin good enough for wind-tunnel tests

A heavily filled composite stereo-lithography (SL) resin from DSM Somos, Elgin, Ill., let the Italian rapid-prototyping service bureau Provel s.r.l. test a scaled prototype of the M346 trainer aircraft in a wind tunnel. A scale model of the Alenia Aermacchi M-346 trainer was built in several sections and assembled using an adhesive specially designed for the ceramic-filled ProtoToolT 20L stereo-lithography resin. M-346 is the most advanced fighter trainer in the world. It features a variety of unconventional attributes along with advanced technologies and avionics that reportedly let it perform better than existing trainers. The creation of an accurate, scaled prototype for wind-tunnel testing was essential to the development process. The inherent complexity of the M-346 prototype made Provel decide to produce the model using SL rather than a powder-sintering technique. ProtoToolT 20L is a ceramic-filled resin that forms highly stiff and dimensionally accurate parts. It has a modulus of 10,000 MPa, a linear shrinkage of under 0.025 mm (0.00098 in.), and a heat-deflection temperature of 279°C (534°F). The dimensions for the scaled model of the M-346 aircraft are 1 × 1 × 0.2 m (3.3 × 3.3 × 0.66 ft). Some parts were much larger than SL equipment permits, so the model was built in several pieces and assembled. The complex stages of creating the partition lines and reassembling the parts were a delicate and crucial aspect of the project, says Francesco Giorgio Buson, managing director of Provel. The accuracy of the Somos composite resin, as well as an adhesive that was adapted for the material, helped ensure an even, high-quality surface finish. "The prototype was ready for tests in less than half the time needed for traditional techniques," says Buson. "The entire project spanned just over two weeks — one week for making the models, another for the finish, assembly,