Mechanical movement in electronic products and structures

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The project aims to develop the use of non-contact contact optical form metrology at Leonardo. This will primarily concern assessing and developing the use of digital image correlation (DIC) to measure movement in external form in order to reveal mechanical properties of materials. This project will develop calibration methods for the use of DIC in combination with a thermal chamber to calculate displacement and coefficients of thermal expansion. It will also assess whether any improvements to the reliability and accuracy of these measurements can be made. Once acceptable methods of measurement have been developed and characterised, this project will then move to assess the its usefulness and limitations of DIC measurements across a range of industrial research applications of particular interest to Leonardo. This will primarily be exploiting DIC technology to reveal properties of Lead free solder and its use in combination with laminate PCBs. These materials are often composite structures of which little is known about their material properties. The information revealed using DIC techniques will be used to develop finite element analysis models of the complex structures measured to improve understanding of future structures and support design digitization endeavors within the company.The calibration provided by the manufacturer for the GOM DIC system is limited to room temperature. For high temperature measurements, there is no qualified testing methodology for the device. Therefore new calibration methodology for the system should be developed. Measurement of coefficients of thermal expansion using a DIC is a non-standard test method and its reliability and versatility as a technique has not fully been explored. The development of a technique to measure CTE using DIC in conjunction with a thermal chamber would enable an accurate non-contact method to inform material properties for improved modelling in the future. The use of a thermal chamber in thermal loading provides a more uniform heat distribution and could provide more accurate CTE measurements with the DIC technology than performed in other studies using heater plates.The measurement of mechanical movement, particularly under thermal loads, reveals further information on composite materials and structures that is otherwise unavailable. This information can be used to inform on reliability and performance of composite structures over their lifetime. This project strives to understand to what extent DIC can be used in the application areas studied and to assess the limitations of the measurement method at the large and small scale. The information provided by DIC technology can also be used to improve the modelling accuracy of finite element models than what is currently available. There is also potential to develop the use of DIC in conjunction with other test methods. This may include direct thermal imaging measurements with a LWIR camera that will require image registration and sensor data fusion at the pixel and information levels. Moreover, combining GOM form distortions measurements with acoustic emissions testing may provide further information on material properties. This would allow the assessment of the limitations of DIC when comparing structures. The addition of acoustic emissions sensors would potentially allow data to be collected on internal material distortion before it becomes visible with the DIC imaging sensors. Used in conjunction, these methods could provide greater understanding on internal stress and external strain in composite structures.