1793. Graphite Phenolic Wing for Medium Range Missiles

Paper

Abstract

Two graphite/phenolic clipped delta wings with a span of 16 in. and root chord of 17.7 in. were fabricated to a typical air-launched medium range missile geometry for the purpose of reducing the weight and increasing specific stiffness of the present solid titanium wing. A longer term objective of establishing production feasibility at comparative or reduced cost was also a concern of the present program. Although no reliable conclusion can yet be reached regarding final production costs of the graphite/phenolic wing, it appears that the graphite/high temperature polymeric wing can be produced at costs competitive with or lower than the titanium wing T300/MX-4961 graphite/phenolic in both fabric and unidirectional form was hand laid over a solid titanium buttress and cured at 325?F in a set of precision steel dies to form the wing. The composite wing weighted 5.7 pounds, including a solid steel shaft, modified from the production wing shaft in order to mate with high temperature static test and wind tunnel test holding fixtures. The weight of the composite wing is 44 percent less than the present titanium wing. Detailed finite element thermal and structural analyses of the laminated composite wing predicted that margins of safety, based on ultimate load and concurrent worst case temperatures, were positive everywhere except at two locations: half span at the forward edge of the titanium insert where fiber tensions and transverse matrix tension strain would be exceeded. However, this result is quite conservative, since linear elastic theory and maximum strains in fiber and matrix at room temperature were used. Negative margins at this location were -0.03 in fiber tension and -0.59 in interlaminar tension. Sub-element tasks were successfully performed on two titanium hub-to-composite designs to help establish the best way to transfer resultant aerodynamic and inertial wing loads through the mid root chord stud-to-missile actuator. Finally, coupon tests in tension, compression, interlaminar and in-lane shear, and flexure were performed to confirm properties used early in the design effort. The coupon test results confirmed that, in general, conservative stresses and moduli were used to develop strain allowable data for use in failure analysis.