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Inspection of Composites - NDT

As the use of composites becomes more prevalent, demand for effective inspection techniques continues to grow. TWI has been at the forefront of research in this area for more than 25 years and possesses a range of technologies for the inspection of different types and applications of composite materials.

The growing uptake of composites has been driven by the need to make light, strong, corrosion- and fatigue-resistant structures. Modern manufacturing processes mean that very complicated shapes can be made in one operation, but this presents challenges for non-destructive testing (NDT).

Both the shape of the part and the orientation of the fibres within can mean that traditional inspection techniques do not work as expected or are too slow to keep up with production.

Composite inspection technologies

TWI has a range of systems aimed at rapid inspection of composite components.

Robotic inspection

The complex geometry of many composite components means that inspection has to be performed manually or by slow immersion tank techniques. TWI has developed an automated inspection system comprising two six axis robotic arms, capable of working independently and cooperatively.

The robotic arms deploy end-effectors carrying ultrasonic transducers (single element and phased array), mounted into water jet nozzles that couple the ultrasound into the part. Software developed in-house generates 3D imaging of the part as well as traditional A- and B-scan data.

Advanced ultrasound

The use of the phased array ultrasonic testing (PAUT) and full matrix capture (FMC) has previously been limited to metals due to the fibres in the material causing the acoustic velocity to vary with angle.

TWI has developed new algorithms that determine and correct for these variations. In addition, the shape of the surface interface can be detected and the refraction occurring is also taken into consideration. This means that high-speed inspection methods using large array probes can greatly increase the speed of inspection and non-zero incident angles can be used for complex shaped components.

FMC can be used where flaw orientation can vary or where high levels of material noise are present.

Pulsed thermography

This non-contact method is very useful for thin-skinned components with complex internal structures, such as stiffeners, honeycomb or foam cores. The images produced look similar to an x-ray and are interpreted using advanced analysis tools and 3D visualisation.

A pair of high-power flash units rapidly heats the surface by a few degrees. A highly sensitive infrared camera monitors the surface as it cools. Features inside the component affect the way this heat dissipates resulting in surface temperature variations that can be processed to generate images.

Laser shearography

Anther non-contact method, shearography uses laser light to detect strain on the component’s surface. Images of unloaded and lightly loaded conditions are compared and fringe patterns are generated. Analysis of the fringe patterns shows how the structure is performing under load. Excitation can be thermal, mechanical, or acoustic.

Summary of our capability

  • Inspection of composite components with complex geometry; large, curved, solid laminates; sandwich constructions with internal structure or cores; and intricately shaped parts
  • Range of methods available to suit different applications
  • Rapid coverage of large areas
  • High levels of structural noise tolerated
  • Thermography and shearography are non-contact
  • 3D imaging

Advanced Engineering and Materials Research Institute

In 2016 TWI announced plans to construct a state-of-the-art engineering inspection and validation facility at its Wales base. The Advanced Engineering and Materials Research Institute (AEMRI) will combine expertise, equipment and resources for bespoke structural testing and evaluation services designed to determine, test and validate the limits of performance of advanced materials and to find ways of saving time, minimising production costs and reducing the risk of structural failure. 

For more information visit  www.aemri.co.uk.

For more information about TWI's NDT services, please email contactus@twi.co.uk.

For more information please email:


contactus@twi.co.uk