International collaboration advances procedural development in NDT of plastics
07/01/2021
The Institute for Plastics Technology (IKT) at the University of Stuttgart has been supplied with a TeraMetrix terahertz system as part of a cooperation with ETher NDE Ltd, Baugh & Weedon Ltd and Springer New Technologies GmbH.
The aim of the current and future collaboration is the application and optimisation of a procedure for non-destructive testing of plastics and fibre-reinforced plastics, as well as the identification of new fields of application.Terahertz radiation is non-ionising, in contrast to X-ray radiation, thus the terahertz test does not require any complex occupational safety measures. However, as with X-ray radiation, plastics are largely transparent for this area of the electromagnetic spectrum, allowing components to be inspected in volume. Unlike ultrasonic testing, terahertz does not require any contact with the test body or any coupling medium and therefore offers great potential for non-destructive testing of electrically non-conductive plastics and coating materials.
The TeraMetrix terahertz system now at the IKT enables tests in transmission and reflection in a frequency range from 0.1 THz to 3 THz. This delivers a broad capability in being able to test and measure material inhomogeneities, density fluctuations and layer thicknesses, as well as fibre waviness in glass fibre-reinforced plastics, which can be detected with great accuracy. Other possible uses range from quantitative testing of adhesive bonds to moisture measurement to 3D reconstruction of entire components.
It is rare for non-destructive evaluation (NDE) to welcome a whole new inspection and measurement technology but, as terahertz technology develops, terahertz inspection systems are being introduced and used in NDT as a cutting-edge inspection technique providing solutions to previously difficult-to-solve applications and measurements.
Baugh & Weedon is now marketing and supporting TeraMetrix terahertz inspection solutions worldwide. It has a testing facility for customers’ samples based in St Albans, UK, and a dedicated expert available to discuss the NDT challenges, which until now may not have been able to be solved with existing methodologies.
Pulsed terahertz imaging can provide a range of information about a sample. It can measure the thickness of a coating as low as ten microns and bonding integrity or provide highly precise multi-layer thickness measurements, all in one pass.TeraMetrix terahertz solutions can also detect the presence of internal voids, a specific gas and moisture content in consumer products and detail the density distribution in a layer of foam, as well as measuring composite repair wraps where individual layers can be resolved.
The key advantage is that terahertz can be used with the most advanced materials and in the most sensitive of testing environments, or where contact is not possible. Due to the low energies in use, there are no associated health or safety risks to personnel or the environment. Terahertz technology provides extremely accurate, reliable and repeatable inspection data.
Applications to date include NDT in aircraft and fibre-reinforced composites, void detection, manufacturing process and quality control, online tyre ply thickness, ceramic coating thickness measurements, inspection and repair of pipeline repair wraps, evaluation of seams and the inspection of radomes and automotive fuel tanks.
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