Fabrication of radar absorbing structure (RAS) using GFR-nano composite and spring-back compensation of hybrid composite RAS shells

The fiber-reinforced composite materials have been advanced to provide excellent mechanical and electromagnetic properties. The radar absorbing structure (RAS) is such an example that satisfies both radar absorbing property and structural characteristics. The absorbing efficiency of RAS can be obtained from selected materials having special absorptive properties and structural characteristics such as multi-layer and stacking sequence. In this research, to develop a RAS, three-phase composites consisted of {glass fiber}/{epoxy}/{nano size carbon materials} were fabricated, and their radar absorbing efficiency was measured on the X-band frequency range (8-12 GHz). Although some of GFR (Glass Fiber-Reinforced)-nano composites showed outstanding absorbing efficiency, during their manufacturing process, undesired thermal deformation (so called spring-back) was produced. The main cause of spring-back is thought to be temperature drop from the cure temperature to the room temperature. In order to reduce spring-back, two types of hybrid composite shells were fabricated with {carbon/epoxy} and {glass/epoxy} composites. Their spring-back was measured by experiment and predicted by finite element analysis (ANSYS). To fabricate desired final geometry, a spring-back compensated mold was designed and manufactured. Using the mold, hybrid composite shells with good dimensional tolerance were fabricated. (C) 2006 Published by Elsevier Ltd.