Graphite Composite Tool Manufacturing at Bell Helicopter Textron

The wide-scale use of Kevlar and graphite . composite structures requires autoclave-worthy long-life tooling. With the inception of large composite structures at Bell Helicopter Textron, many tooling concepts were evaluated. Plastic and metal tools were screened in conjunction with part size and shape. In some cases, such as flat parts and simple contoured parts, metal tooling still has applications regardless of the significant differences in thermal expansion. Compound contoured parts and intricately shaped parts require thermally compatible tools. For these reasons and other considerations, Bell Helicopter Textron initiated a program to evaluate graphite tooling materials and tool manufacturing methods to produce autoclave-worthy bond molds capable of withstanding service temperatures of 400 degrees F, 100 psig pressure for 500 or more production cycles. Preimpregnated graphite fabrics and the wet layup materials and methods were considered and tested. The type of tool construction, such as monolithic and cookie sheet, was evaluated and adapted to particular needs. Additionally, the use and application of tool surface coatings have always been a major concern in the field of plastic tooling. Bell Helicopter Textron has evaluated the standard liquid paste type surface coats and the latest in adhesive film type surface coats.