Composite resin is stiff enough for wind-tunnel tests

Using heavily-filled composite stereolithography resins from DSM Somos, Italian rapid prototyping service bureau Provel is opening up new frontiers in wind-tunnel test applications with the development of a scaled prototype of the new M-346 fighter trainer aircraft for Alenia Aermacchi.

The M-346 is the only new-generation advanced fighter trainer in the world. With a variety of unconventional attributes, advanced technologies and avionics, the M346 delivers superior performance over existing advanced trainers. However, essential to the development process was the creation of an accurate, scaled prototype for effective wind-tunnel testing.

Based on the inherent complexity of the prototype design, Provel chose to produce the model using the DSM Somos composite stereolithography resin ProtoTool 20L, rather than the popular powder sintering technique.

Ceramic-filled resin

Coming from the Somos family of ProtoComposites materials, ProtoTool 20L is a ceramic-filled resin that is capable of producing highly stiff and accurate parts. With a modulus of 10,000MPa, a linear shrinkage of

Francesco Giorgio Buson, Managing Director of Provel, comments: "Somos ProtoComposites materials have the mechanical properties – particularly the dimensional and structural stability – that are essential for these kinds of aerodynamic tests."

The dimensions required for the scaled model of the M-346 were 1000 x 1000 x 200mm. Because some parts were much larger than stereolithography equipment will permit, the model was constructed in several pieces and then assembled. The complex stages of creating the partition lines and reassembling the parts were a delicate and crucial aspect of the project, helped by the accuracy of the Somos composite resin, as well as an adhesive that was specially adapted for the material to ensure an even and high-quality surface finish.

Savings in time and cost

Perhaps the most important advantage provided by the ProtoComposites material during development of the M-346 model was the overall time and cost savings achieved.

Buson says: "The ProtoTool prototype was ready for aerodynamic tests in less than half the time that would have been required using a traditional technique. The entire project could be completed in just over two weeks: one week for production of the models and another for the finish, assembly and dimensional check."

As a result, the final cost analysis on producing the M-346 model with ProtoTool demonstrated a cost savings of more than 30 per cent. Buson adds: "Producing a model of this type using conventional technology would have taken several months for its design and development, costing several hundred thousand euros."

As a result of the shorter implementation time, as well as the functional and aesthetic results produced by the Somos material, Alenia Aermacchi now considers ProtoTool 20L stereolithography resin a standard for creating wind tunnel test parts for their aircraft designs.

About Provel

Provel www.provel.it and its subsidiaries are a leading Italian group engaged in the construction of rapid prototypes and tools for the automotive industry, and have been a strong presence in all the industrial and design sectors for over twenty years.