Tool Wear in the Machining of Aramid Honeycomb
Aramid honeycomb is an important material because of its low density, high strength, high combustion temperature, and ability to absorb energy, both kinetic and acoustic. Because of these properties, it is used in the aerospace and marine industries – primarily in high performance applications. With the transportation economy moving toward electric vehicles for terrestrial, aquatic, and aerospace, it is likely that aramid honeycomb will become even more important. However, these structures are currently quite expensive to produce, especially when they contain complex shapes that require machining of the honeycomb. One reason is that the tools suffer a very high rate of tool wear which is surprising since the tools are carbide and the honeycomb is somewhat like cutting paper – and even mostly cutting air. Our research focus is to determine the cause of the high rate of tool wear and to develop methods and tools that will reduce the cost of honeycomb machining.
Additive Manufacturing
The group has studied many aspects of additive manufacturing including FEA modeling of 3D printed parts using the modified Classical Lamination Theory, methods of sectioning parts without damaging the as-deposited internal structure. One area that has received considerable interest is the use of Co-Printed Test Specimens as surrogates for complex part characterization. The development of co-printed specimens that adequately match part performance but do not adversely affect the build of the part is quite challenging and requires careful thought and may require different part models and strategies for different applications.
Direct Rapid Tooling by Foam (DRT-Foam) Extrusion
Large scale plug and mold fabrication for low production quantity composite layups is often done through a tedious and manual process in which large blocks of foam are glued together and then machined to the final shape needed for the mold. This process requires adhesive between the foam blocks, cutting of foam blocks to mimic the final shape, and then significant machining time to achieve the final shape from the blocks. The foams used are often polyurethane foams because of their strength and high temperature capability for the autoclave. Because polyurethane foams are not biodegradable, the waste from the block process is landfill material and will be around for a long time. To reduce the amount of waste and the production time, the DRT-Foam process seeks to make a near-net shape mold out of foam. While still requiring final machining, the near net-shape will require minimal machining time and will also produce much less waste. The foam machine deposits the foam in “roads” like other 3D printing or additive manufacturing techniques and creates the mold line by line and layer by layer.