Laser-ultrasonic testing is a non-contact, non-destructive testing (NDT) technique that allows for the high-speed inspection of complex geometries and materials in harsh environments. The technique uses two lasers; one to generate an ultrasound and the other to detect it. This testing method provides detailed, high-resolution mapping of defects like cracks, delamination, and voids without needing a couplant or immersion, making it suitable for the inspection of hot, moving, or irregular surfaces.
A versatile inspection technique, laser ultrasonic testing can be used with metals, composites, ceramics, and semiconductors, and has found applications in industries including aerospace, automotive, rail, and nuclear.
TWI has expertise in laser ultrasonic testing, which we have used within a range of different projects for the benefit of our Industrial Members and for industry as a whole. These include core research programme (CRP) projects, joint industry projects (JIPs), public-funded projects, and those undertaken specifically for the benefit of particular Industrial Members.
Although some of our work is necessarily confidential in nature, there are still some examples of work conducted at TWI related to laser ultrasonic testing, as follows…
Joint Industry Projects
Our JIPs are designed to allow interested parties to join as sponsors in return for access to the project outcomes and the opportunity to provide input into direction of the projects themselves.
- Support to the IntACom™ 3 JIP
This JIP was one in a series of projects under the moniker of ‘IntAcom’ that were focused on the development of automated, robotic non-destructive testing systems. IntACom 3, ‘Improving the Inspectibility of Aerospace Composite Materials’ had the goal of reducing the time and cost associated with inspecting geometrically complex components. To solve this challenge, we incorporated co-operative robots (cobots), multiple inspection methods including laser ultrasonic testing, and advanced software to improve testing throughput and accuracy for both in-service and manufacturing requirements.
Public-Funded Projects
Our expert teams are also called to participate in public funded projects, where we partner with other organisations from industry and academia to solve specific challenges.
- OpenHybrid Project
Laser ultrasonic testing was performed as part of this project, which ran from 2016-2019 with the aim of creating a new hybrid additive and subtractive manufacturing system capable of integration onto any machine tool platform. The project team sought to increase the impact and uptake of hybrid AM technology for a wider range of machine tool platforms, processes, materials and applications through the development of a single manufacturing system capable of producing large, high volume and complex components without the need for materials handling or post-processing. The multi-tool platform used directed energy deposition (DED) additive manufacturing with an integrated machining process to enable fully finished components to be produced. The laser cladding technology employed offers high deposition rates, material flexibility, minimal substrate interaction, and is also an effective repair technique (Figure 1).
- Non-Destructive Testing of Hybrid Composite Structures
The ACCURATe Project (2017-2022) used laser ultrasonic testing to address a non-destructive testing challenge for the aerospace industry. Composite materials such as carbon fibre reinforced polymers and hybrid polymer-metal multilayer sandwich structures (laminates) has been shown to offer much greater fatigue strength to weight ratio and elastic modulus to weight ratio than metals. Because of this, they were highlighted as a key pathway to reducing aerospace fuel costs and emissions, with state-of-the-art aircraft containing up to 80% by weight of such composites in their load bearing structures at the time of the project. However, there were two key barriers to overcome: (i) they are more expensive that traditional aluminium alloy structures and (ii) the risks of the development of both internal defects and impact damage leading to structural failure are higher. This TWI-led project created a prototype system for fast and contactless NDT of these structures during manufacture, including the design of generating and detection laser systems, the creation of analysis software (with post processing applications), and the design of an inspection cell with a robotic arm to manipulate the laser systems (Figure 2). The innovative system was validated through the inspection of a fuselage barrel demonstrator component panel.