In the aerospace industry contactless measurement has been a very versatile and adaptable in recent years, mainly because of its diverse applications. Usually ultrasonic measurement requires acoustic contact media which may disserve the sample and varies for different materials. In the operational hand, acoustic contact media like water is also not preferred for on-aircraft inspection. The air coupled inspection technique among other nondestructive testing techniques is often not enticing due to acoustic mismatch and wave propagation. Though, acoustical mismatch of the transducers can be reduced by application of a matching layer and also by using different corresponding transducers. Air-coupled transducers are the captivating alternatives for the inspection. This paper comprises different air coupled inspection techniques i.e. through transmission and guided wave generation as well as its working modes. Various transducer arrangements, the advantages of air-coupled ultrasonic guided wave inspection over other NDT techniques and their specifications are discussed revolving around the materials. Composite materials have superior properties like tensile strength, better heat resistance which cannot be materialized in single. The utilization of composite materials like CFRP, GFRP, other polymers and ceramic composites seeks the improvement in lift to weight ratio. An overall review deals with air coupled techniques and scrutiny of different materials concerning this technique, which includes characteristics of various composite materials used in aerospace industry.

The objective of the research study is to model a bridge with four different material using ANSYS software and to perform a modal analysis of bridge problem. For all four materials eight node solid element is selected and meshing is done individually for each modal. The material property of each material is selected as per literature database in ANSYS software. The modal analysis in ANSYS is performed to obtain the natural frequency and mode shapes of bridge to avoid the resonance of the bridge.

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