Friday, September 1, 2006
TOOL CRIB SPECIAL REPORT: Composite Tooling
Name of the Game: Right Selection of Rapid Repair Tooling
Formglas CNC Patterns Division's Kevin MacMillan, manager of business development, believes the most commonly misunderstood aspects of rapid composite repair tooling are tool system selection, determining part yield, and achieving reasonable tolerances. In his view, having the right tools for the job is the name of the game. Formglas offers several rapid tooling products, including the low cost tooling for composites (LCTC) method for creating "soft" layup molds from compounded patties. LCTC was originally developed by Boeing (AM, March 2002), and Formglas CNC cut some of the first direct molds from the material. MacMillan reports that Formglas has improved upon the Boeing tooling system through enhanced oven airflow, patty distribution techniques and allowances for base construction and machining.
Composite Tooling Takes Shape
Rapid tooling options for composite repair from Airtech International's Advanced Materials Group include Impression-Master, a reusable rubber tooling membrane that takes and holds any shape under vacuum, and then returns to original shape for hundreds of repeated tooling uses if handled correctly. Originally developed by Lockheed and the Air Force Materiels Research Lab for battle damage repair, this tooling method is now available for composite laminate patch repair in both commercial and military aircraft. With room-temperature initial cure and resin infusion, another Airtech product, Toolfusion, beats the cost of composite prepreg tooling by 40% by eliminating freezer storage and out-life issues. The company also offers its Toolmaster line of wet lay-up epoxies for rapid repair tooling construction.
Water-Soluble Composite Tooling on Tap
Advanced Ceramics Research (ACR) has developed water-soluble materials for production or repair tooling in its AquaPour, AquaCore and AquaSeal products. Castable, non-corrosive AquaPour, a powder mixed with water that becomes pourable and injectable, can be autoclave cured at up to 380?F and pressure of 125 psi, or cured in a convection oven. The material then washes out readily with tap water. For making mandrels and tooling molds for filament wound or resin transfer molded composite parts, AquaPour has demonstrated compatibility with all commercial resins and prepreg compounds. The company reports improving tool dry time by 10%, and development of tooling formulations to accommodate resins such as bismaleimide (BMI) in composite parts that must withstand high compressive strength and high performance temperatures. Boeing is testing the water-soluble tooling materials strictly for composite repair; another major OEM is using AquaPour for large-part repair, such as total core delamination on body fairings. Jeff Campbell, composites engineer for ACR, has no doubt that this repair technology developed by the military will find its way to commercial operators and OEMs, especially for thicker composite cross-sections now being designed into new commercial airliners.
2Phase Expects Tech Transfer from Military
2Phase Technologies, Inc., is in its third year of a U.S. Army Advanced Aviation Technology Directorate contract. The company has developed single-sided reconfigurable tooling for depot-level composite repair, as well as for replication of composite parts on legacy aircraft. The tooling material undergoes multiple state changes: from a liquid-like state to a solid at room temperature, at which stage it can be used to form fixture tools for part repair, or to form full part templates. If needed, a hard ceramic-state tool can be formed via heat cure of 250?F over two to four hours, that offers permanent maintainability and multiple autoclave cycles at up to 350?F. When the tool is no longer needed, it can be returned to the initial formable liquid state in a matter of minutes at room temperature. This reversibility makes the tooling material especially useful for mandrels or trapped tools.
Reconfigurable Tooling for Composites
U.S. Army, Navy and Air Force repair depots are testing the 2Phase tooling system on non-structural composite parts such as hatch covers, radomes, and panels. Without altering currently approved repair procedures, the 2Phase reconfigurable tooling material can be substituted in repair fixtures to provide depots with flexible, low-cost repair solutions and to reduce tool inventories. 2Phase has also developed a portable splash tool that can accurately capture damage on an aircraft, and then be cured in order to create a single-sided, negative image template for a composite patch that matches the contour of the damage. Current single-sided 2Phase toolbeds range in size from 1.5 by 2 ft to 6 ft by 9 ft, for forming either a male or female mold with 2 ft depth of draw. John Crowley, president and CEO of 2Phase, believes this technology will be used in commercial aircraft repair once development and implementation by the military has taken place.
Technology for Composite Patches That "Self Repair"
Dr. Carolyn Dry, president of Natural Process Design, Inc., developed patents in the 1990s for self repair materials, and is now embedding small tubes of adhesives in composite laminates that, upon impact, can seal a delamination, hole, or crack while an aircraft is in flight. The process is suitable for a small repair patch in composite skin areas that may see frequent damage. After Phase II of an Air Force Small Business Innovative Research (SBIR) contract in the next several years, Dry expects to begin technology licensing of the process. Richard Holzwarth and Edwin Forster are the project monitors at the Wright Patterson Air Vehicles Directorate. Refinements to the technology include selecting an adhesive or repair chemistry to withstand processing temperatures between 300?F and 350?F, decreasing embedded tube size so as to reduce effects upon laminate properties, and improving adhesive set-up time to 30 seconds or less. Dry also reports that when damage is relatively small, the tubes demonstrate recognition of the amount of adhesive to release, and can actually provide "self repair" more than once in a damaged area of a composite part. email@example.com.