Novel Integrated Imaging Approaches for Damage Characterisation of Composite Materials and Structures

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Fibre reinforced polymer (FRP) composite materials are widely used for aero, marine, transportation and energy structure applications. They exhibit high stiffness and strength relative to their weight, and excellent performance when subjected to fatigue loads. A significant drawback is understanding how damage evolves in the materials and the ability to assess if a component should be repaired or continue in service. The outcome is conservative design and unnecessary scrap at the manufacturing stage. Efforts have been made to better assess composite structures using a variety of non-destructive evaluation (NDE) techniques. However the industrially desired 'one stop shop' for inspection has remained elusive. The current industrially preferred technique in the aerospace and wind turbine sectors is ultrasound, and in the shipping sector simple tap tests are often used. The limitation of current techniques (such as ultrasound (UT)) is they cannot provide details on how damage or defects evolve and affect the service life of a component. The PhD project aims at developing an idea known as 'Strain-based NDE'. Here full field imaging techniques are used to capture data that is directly related to the strain caused by the damage to provide prognostic information on the effect of damage. The system will enable decisions to be made on scrap/repair/continue in service. A focus is reducing the cost of such a system by replacing expensive IR detectors with low cost bolometers. A major challenge is the integration of the images collected by white light and infrared imaging. It is well known that composite materials behave differently when they are constructed into a large structure of complex shape and subjected to multi-axial loading. The strain based NDE technique has been demonstrated on simple components so the purpose of this project is to examine actual structural components of complex geometry and characterise the material damage state in-situ.