The use of polymer-matrix composite (PMC) materials by the Department of Defense (DoD) and Department of Energy is on the verge of an unprecedented increase. Current and recently completed Advanced Technology Demonstrator programs could be in production within the next 5-15 years, consuming thousands of tons of PMC raw materials per year and, in the process, creating hundreds of tons of waste materials. Some of the PMC components in these programs were designed, or are currently being designed, using existing technologies that fail to provide for practical and affordable component repair.
The objective of this project was to research, develop, and demonstrate unique, affordable, and environmentally friendly families of PMC manufacturing and repair technologies for stand-alone repair of current, soon-to-befielded, and future DoD structures.
The primary technologies matured during this project included induction processing of carbon fiber/thermoplastic resin laminates, induction heating and curing of adhesives for composite repair, and electron beam (EB) processing for low-cost remanufacturing and repair of composite structures. Induction and EB processing focused on materials substitution as a means of eliminating hazardous materials from composite manufacturing at the raw materials level. Induction processing allowed a high temperature thermoplastic replacement for traditionally thermoset resins to be achieved with improved product performance. Because thermoplastics logistically are more difficult to process, heating models for thermoplastic impregnated carbon fiber laminates were developed that allowed through-thickness heating in the thermoplastic processing zone. Consequently, induction-processed products resulted in lower cycle times and decreased scrap rates. High performance composite precursor materials (e.g., adhesives, vacuum infusion resins and prepregs) then were formulated for processing by EB irradiation. These new thermoset materials possess near infinite room temperature stability, facilitating reduced wastes due to spoilage. EB cure methods and mechanisms also were explored, and demonstration products validated EB processing potentials. EB repair and remanufacturing methods were established for selected ground and air vehicle applications.
This project succeeded in providing potential solutions for both EB curing and induction processing of composites. Many of the formulated material solutions are now available commercially through Applied Poleramic, Inc. in Benicia, CA. Induction-based processing of thermoplastic carbon fiber laminates was accomplished by commercial partners at Alliant Tech Systems, where induction processing is now actively used in the manufacture of Army composite structures. This project was completed in FY 2001.
This project represents a potential annual savings for the DoD of $15B by the year 2028, based on current composite platforms. However, with the increasing implementation of structural composites in DoD combat platforms, the magnitude of impact could become ten times as significant. Additional project benefits include the following: (1) unlimited resin shelf life and elimination of associated waste; (2) reduced pollutant manufacturing and increased repair technologies resulting from new materials and curing methods; (3) a significant reduction in manufacturing waste and emissions for multifunctional composite structures; and (4) compliance with increasingly stringent processing emissions standards for composite facilities.