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Composite Inspection

By their nature composite materials are inhomogeneous, it is therefore necessary to use composite inspection methods which can distinguish between relevant defects and inherent material variations. Due to their structure, some composite materials are difficult to get sound through so the inspection method selected must be tailored to the individual circumstances. Even superficially similar structures can behave quite differently when being tested. Sonatest can provide several solutions to Composite Inspection requirements from their core product range. Additionally due to varied experience within this field Sonatest are also happy and confident to provide application focussed and bespoke solutions.

Sonatest Ltd will be exhibiting at Composites and Aero Engineering 2011 at the Birmingham NEC, November 9th - 10th  2011.  To find out more about our equipment capabilities and bespoke solutions for aerospace and composite inspection visit us on stand 539.

Monolithic composites such as Glass or Carbon reinforced plastics often have low enough acoustic scattering that a clear ‘back wall echo’ can be obtained, so these materials can frequently be inspected using ‘standard’ pulse echo ultrasonic methods. For manual inspection Ultrasonic Flaw Detectors such as the Sitescan 250 or Masterscan 350 can be used. These can also be used as the instrumentation package within an automated scanning system, which is required for most production applications. Typically this would use an immersion tank and a Masterscan 380.

The RapidScan 2 system is an extremely fast and convenient way of producing a C-scan of flat or nearly flat materials. This uses an Array Probe and a polymer wheel assembly to manually scan the part. Typically a 50mm wide sensitive area can scan at around 3-400 mm per second, producing a scan rate of around 1 square meter per minute. The RapidScan 3D enhances this further, by using a coordinate measurement arm to assemble a large C-scan from Multiple passes over a three dimensional surface.

More highly scattering materials such as Aramid-fibre (Kevlar) based ballistic Materials, or sandwich structures such as foam or honeycomb filled composites, cannot be tested in pulse echo mode. The level of scattered sound masks reflections from defects. For these a through transmission approach is needed. This requires two aligned probes, one on each side of the material. Disbonds or similar defects will block the sound completely. In many cases a water coupled squirter’ system can be used. While water coupling is convenient, and acceptable for many applications, some materials are not compatible with water. In these situations Sonatest can provide solutions using the Dryscan 410D system, combined with a pair of rubber faced spot or roller probes to couple sound to the part.