Composites are being used at a very high increasing rate where the weight to strength ratios is critical. As a result of the increase of the composites use, such as the Boeing 787 which is comprised of nearly 50% composite structures, a better knowledge and behavioral prediction is desired. This can be done through computational models and/or physical testing. Numerous FEA programs are used to aid in the design process and to predict the performance and behavior of composite structures. There are also many non destructive methods of investigation (NDI) which are used in both quality control and behavioral observations.
A composite flight structure common to many airplanes is a radome, which can be defined as a structural enclosure used to protect an antenna from the environment which includes the aerodynamic loading and weather. The specific radome being tested is a SAT-COM radome used on aircraft such as Boeing 767-777 & Airbus A320, A330 and A340. It is desired to perform vibration testing as well as internal pressure testing to correlate the FEA models used in the design of the radome. This is completed by performing 2 different types of NDI (Shearography & Vibrometry) and 1 vacuum pressure test. The results are compared and used to validate the current FEA model.
Shearography allows us to measure the surface deformation of an object when under a stress. Shearography was completed to determine any possible defects caused in manufacturing (or transporting) the radome. De-lamination will possibly cause unpredicted response in the vibration or pressure tests. Areas of different construction as well as defects will deflect non-uniformly. There were no flaws detected in the composite radome tested.
Laser Doppler Vibrometry (LDV) is a non-contact vibration measurement that is used to determine the natural frequencies and mode shapes of the Composite Radome Structure. The vibration testing was completed using a few different boundary conditions which include approximately free-free BC’s and fixed BC’s. The testing has corresponded accurately in comparison to the FEA model however; it is suspected that there is some slight error caused by the fixed fixture for vibration testing.