Evaluation of Partial Interface De-Bonding Using Multi-layer Laser Flash Analysis
Creators: name: Farooqui, Ateeb Fareed
Publisher: name: University of Surrey
Year: 2023

description: Delamination of interlayers in multi-layer systems can lead to functional, stability, and lifespan degradation of the system, especially at high temperatures. Laser flash analysis (LFA) has long been used for thermophysical property measurements at high temperatures. Multi-layer reference artefacts, with and without, debonded regions are required for validating the thermal characterisation of such systems using LFA. Such artefacts would aid in developing a methodology that will be able to evaluate, simulate and predict the thermal response and performance of multi-layer systems with and without defects at high temperatures.<br>
description: <br>
description: This thesis presents the development and validation of a methodology for characterisation of the thermal interface resistance of bonded and debonded regions of laser flash analysis artefacts. Additionally, it details the criteria, design, development, and characterisation for two candidate high temperature multi-layer laser flash reference artefacts, a graphite-hafnium foil and a silicon carbide-molybdenum foil system.<br>
description: <br>
description: The methodology developed employs an inverse model approach, where a simulated dataset is fitted iteratively to an experimental dataset by incrementing the thermal interface resistance until a good fit is achieved. A sensitivity study was conducted to identify sensitive parameters. The methodology was consistent in determining the interface resistance of bonded and deboned regions and was demonstrated on multi-layer artefacts at high temperatures.<br>
description: <br>
description: Using spark plasma sintering, high-temperature multi-layer LFA artefacts with and without defined debonds were created for both the graphite-hafnium foil and silicon carbide-molybdenum foil-based systems. Both systems were shown to be useable above 1000 °C and demonstrated reproducible thermal responses as measured by LFA at all measured temperatures. Additionally, the physical structure, including the debonded regions, was imaged using scanning acoustic microscopy to assess uniformity between artefacts.<br>
description: <br>
description: The thermal stability of both systems was assessed by thermally cycling artefacts during LFA measurements. The graphite-hafnium foil-based system had poor thermal stability, with the thermal response deteriorating after a minimum of two thermal cycles. The point of failure was shown to be the interface between the graphite and hafnium layers. In contrast, the silicon carbide-molybdenum foil-based system exhibited excellent thermal stability up to ten heat cycles. The silicon carbide-molybdenum foil-based system was shown to meet all the necessary criteria, making it an ideal candidate for a high temperature multi-layer LFA reference artefact.<br>
description: <br>
description: This work was in partnership with the National Physical Laboratory (NPL) as part of a European Metrology Programme for Innovation and Research (EMPIR) funded Joint Research Project (JRP) 17IND11 Hi-TRACE. <br>