Cost Effective Advanced Structures By Braiding

As the technology of composite materials matures, and the applications become quite wide-spread throughout the aerospace industry, the demand for lower cost has become a major driver in all production programs involving composite materials. The history of rapidly escalating costs for the sake of performance gains is no longer an acceptable tenant. Production techniques that reduce component costs by both automated production and lower material costs are absolutely essential to the achievement of advanced structures that are affordable. One technique that offers great promise in this area is automated braiding. While basic braiding technology has been used in the textile industry for many years, computer control of the process and its application to advanced structures is a new thrust that promises significant advantages. Braiding of complex shapes with abrupt tapers, flanges and shape changes are possible. The flexibility of the process permits braiding of prepreg roving or using dry fibers followed by resin transfer molding or other impregnation methods. The choice of materials is influenced by material cost and labor manhour content, as they affect the total price and structural integrity of the end product. For many composite structures, the acquisition cost is the combination of the labor hours to cut, laydown, bag and cure the many detailed structural elements, which are necessary to make a complete weight efficient structure. Automation of these processes by various tape laying machines has been attempted with some success. Complex shapes with high curvature is a class of structures not readily amenable to automated tape laying. The braiding machine has the capability to fabricate high curvature complex shapes with minimal labor content. The braiding of non-circular cross-sections is readily accmplished and many other structural components are excellent candidates for cost effective production for the braiding process. Helicopter rotor blades and rotor blade spars are examples of such structures. It is concluded that certain classes of advanced composite structures are readily produced by a very cost effective means, using automated braiding. Acquisition costs of such elements can be significantly less than that demonstrated by other composite production techniques for the same components, without sacrifice of structural material properties or performance.