Advanced materials are a necessity, but so is a viable industrial base
Declining defence budgets mean the military is no longer the major customer for many sectors of the US industrial base. AFRL's Materials and Manufacturing directorate (ML) is responding to the challenge by finding ways to ensure the industrial base can still supply the Department of Defense's needs.
ML is split into four research divisions, and Manufacturing Technology and Systems Support divisions - the latter described as unique in being dedicated to supporting acquisition offices, logistics centres and the USAF in the field. As a result it provides real-time problem solving to ensure that issues do not have an adverse effect on the USAF's readiness. It provides failure analysis of structures, materials and electronics. Both civilian and military accident investigators use this capability to help determine accident causes.
The function of the Manufacturing Technology division is to derive new processes and practices, particularly for lean manufacturing needs. The research divisions, meanwhile, cover non-metallic materials; metals, ceramics and non-destructive evaluation; survivability and sensor materials; and airbase and environmental technology.
ML Integration and Operations division chief George Schmit says with smaller numbers of weapon systems being acquired, and remaining in service for longer, the DoD is no longer the major customer for some industries. Furthermore, it is the only customer for some materials, but does not acquire sufficient quantities to sustain the industrial base. To counter this ML has developed lean manufacturing techniques and is finding ways to ensure that the industrial base can supply the DoD's needs. For instance, an area of concern is advanced composites. ML has developed a method for repairing damaged wings using carbonfibre epoxy patches, and has also adapted the material to civil engineering applications - such as refurbishing bridges or earthquake-proofing bridge supports in California. This has involved educating civil engineers who have traditionally dealt with only concrete and steel, says Schmitt.
A practical example is the replacement of a bridge's horizontal deck. Previously this would be a major job that would require roads to be closed for long periods and much of the support structure to be rebuilt as well as the deck. ML developed a composite deck that simply drops into place on the existing supports. An AFRL engineer also helped the US National Composites Center develop a health and usage monitoring system that allows real-time condition monitoring of composite structures.
Highly conductive polymers
Schmitt says ML's polymer development work includes investigating the use of highly conductive polymers to replace copper in aircraft wiring, which should save weight, improve payload and reduce fuel consumption. Introduction of these polymers is some way off, as they have to remain conductive through an aircraft's life in an environment that is not conducive to the material retaining its properties.
Polymers could also be used for lightweight deployable structures on satellites. ML is working to derive materials capable of withstanding the space environment and which have the structural integrity to form high-pointing-accuracy antennas. Schmitt says there is also interest in replacing the glass or organic-material substrates used in solar cells with polymers to significantly reduce weight.
"We're still working on composite structural materials. There is a never-ending emphasis on making them affordable," says Schmitt. ML is studying a range of initiatives to reduce manufacturing costs, including curing with ultraviolet light or electron beam welding instead of using autoclaves.
Embryonic work with Defense Advanced Research Projects Agency is investigating the potential of amorphous aluminium, says Schmitt. The aim is to create aluminium with a non-crystalline structure, to provide better crack resistance. In traditional metals, cracks are initiated at, and travel along, crystal edges.
Perhaps ML's most pervasive issue is material affordability. The time taken to develop a new material from "a gleam in someone's eye to being used in systems", typically around 15 years, makes development expensive. ML is aiming to change this, says Schmitt, by integrating the end-user into the whole process to ensure the customer receives what it wants, and by using computer modelling and simulation to reduce the thousands of tests that were once required to develop a database of a material's properties.
Source: Flight International
