Out-of-Autoclave Method Cures Materials and Cost Concerns Alike

  • Published
  • By Heyward Burnett
  • Materials and Manufacturing
WRIGHT-PATTERSON AIR FORCE BASE, Ohio --  Air Force Research Laboratory Manufacturing Technology engineers expect a recent breakthrough in bismaleimide resin technology to generate significant improvements in the cost and fabrication of high-performance composite aerospace structures. The discovery eliminates the need for BMI composites to be cured in an autoclave; this out-of-autoclave processing capability expands the resin's use for much larger components, as well as for field- and depot-level repairs that are currently very difficult to perform. The new technology also dramatically lowers costs, both in terms of the enormous capital investment needed for acquiring new autoclaves and with respect to the price tag of components and their constituent materials.

The BMI advance stems from a collaborative effort between ManTech, the Defense-Wide Manufacturing Science and Technology program, and Stratton Composite Solutions to reduce the weight and increase the structural performance of aerospace components. The same parties are now focused on further reducing the costs related to their groundbreaking capability, which could feasibly reduce the cost of BMI-based materials and composite component manufacturing by 40% and 30%, respectively.

BMI resins presently require autoclave curing to achieve aerospace quality; however, the many large autoclaves owned by the Air Force are already in use for existing systems and therefore inaccessible to new demand. Unfortunately, purchasing new autoclaves is extremely expensive, and there are also limits to the size of units that can be safely built and operated. Accordingly, the availability of a new processing capability--one that avoids autoclave curing altogether--is a positive force in decreasing capital expenditures. In addition to lowering equipment-related expenses, the out-of-autoclave technology increases the materials supplier base and, consequently, lowers direct materials costs. The method nets indirect savings, too. Specifically, the replacement of epoxy resins with BMIs enables bigger components to be fabricated, which significantly reduces the number of subassemblies required and drives the price of aerospace structures even lower. The new processing approach addresses other shortcomings as well, not the least of which has been the lack of a viable technique for repairing BMI components on the flight line and in the many forward depots where autoclave processing is not a possibility.

The government/industry team's initial composite processing and mechanical testing demonstrates promising results for the technology. Fabrication of a part built with existing tooling is currently under way, with AFRL and Stratton Composite Solutions slated to complete this process in May 2011.