Identification of the Anisotropic Rigidities and Damping of Composite Panels for Radomes and Shelters

Advanced Composite shelter and radome designs save large sums of money because they do not corrode, and are highly movable. Moving them does not require the energy and fuel costs once associated with their steel counterparts and their maintenance can be done in the field with almost no exceptions. Composite shelters and radomes make use of sandwich panels because they combine great stiffness and strength with low signal attenuation. The anisotropic rigidities and the damping of sandwich panels have proven to be very important for their successful utilization. Nevertheless the identification of these properties is difficult, cumbersome, and expensive. This Phase I SBIR outlines a new approach. The idea is to use a finite element program “backwards.” A procedure has been outlined for the very precise measurement of resonant frequencies. Using these frequencies as input, the sandwich panel stiffness and shear properties may be calculated by using a methodology which will be developed during the phase-I research. In addition to the rigidities, a procedure will be developed to measure precise materials damping coefficients. Since the rigidities and damping coefficients are dependent on sandwich panel type (thermoset or thermoplastic), quality and extreme temperature conditions this characterization method may also provide to be a powerful tool for sandwich panel quality inspection.