Mechanical movement in electronic products and structures

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.

Complementing our Pathways to Impact document, here we state the expected real-world impact, which is of course the leading priority for our industrial partners. Their confidence that the proposed CDT will deliver valuable scientific, engineering and commercial impact is emphasized by their overwhelming financial support (£4.38M from industry in the form of cash contributions, and further in-kind support of £5.56M).

Here we summarize what will be the impacts expected from the proposed CDT.

(1) Impact on People
(a) Students
The CDT will have its major impact on the students themselves, by providing them with new understanding, skills and abilities (technical, business, professional), and by enhancing their employability.
(b) The UK public
The engagement planned in the CDT will educate and inform the general public about the high quality science and engineering being pursued by researchers in the CDT, and will also contribute to raising the profile of this mode of doctoral training -- particularly important since the public have limited awareness of the mechanisms through which research scientists are trained.

(2) Impact on Knowledge
New scientific knowledge and engineering know-how will be generated by the CDT. Theses, conference / journal papers and patents will be published to disseminate this knowledge.

(3) Impact on UK industry and economy
UK companies will gain a competitive advantage by using know-how and new techniques generated by CDT researchers.
Companies will also gain from improved recruitment and retention of high quality staff.
Longer term economic impacts will be felt as increased turnover and profitability for companies, and perhaps other impacts such as the generation / segmentation of new markets, and companies receiving inward investment for new products.

(4) Impact on Society
Photonic imaging, sensing and related devices and analytical techniques underpin many of products and services that UK industry markets either to consumers or to other businesses. Reskilling of the workforce with an emphasis on promoting technical leadership is central to EPSRC's Productive Nation prosperity outcome, and our CDT will achieve exactly this through its development of future industrially engaged scientists, engineers and innovators. The impact that these individuals will have on society will be manifested through their contribution to the creation of new products and services that improve the quality of life in sectors like transport, dependable energy networks, security and communications.

Greater internationalisation of the cohort of CDT researchers is expected from some of the CDT activities (e.g. international summer schools), with the potential impact of greater collaboration in the future between the next generations of UK and international researchers.