Material Processing using Laser Induced Droplet Vaporization

There is an increasing demand for high performance materials many of which are incompatible with conventional manufacturing processes due to their sensitivity with heat and abrasion (e.g. carbon fibre reinforced polymer (CFRP), polymers, thin films, semiconductor wafers). Surface preparation of these advanced materials is usually essential to exploiting their enhanced properties in engineering applications. This project concerns the development of a new, low temperature material processing technique using impulsive shock waves of liquid vapour as a generic manufacturing tool, called material processing by laser induced droplet vaporisation (LIDV). LIDV uses a pulsed laser to vaporise a stream of droplets to produce a succession of impacting shock waves at the surface of the component of interest. By exploiting the precision of modern droplet generation technologies with the power and control of a laser source, well-regulated impulsive forces can be achieved at a level sufficient to remove surface contaminants and/or to modify the surface mechanical properties (roughness and hardness). The project will undertake proof-of-principle experiments to establish the benefits of LIDV as a means to clean and modify the surface of CFRP. CFRP presents a particular problem since a multi-stage surface preparation process is required as all traces of surface contaminants and chemical agents that are exhumed during production must be removed before final assembly. It is expected that the LIDV process could provide more accurate and efficient surface modification of high performance materials than at present and that it will also open the door for exciting breakthroughs in peening, thin films transfer, hardening and alloying.

The proposed research project on material processing using laser induced droplet vaporization (LIDV) is expected to have a significant impact at many levels. This project concerns the development of a new manufacturing process using impulsive shock waves of liquid vapour as a generic manufacturing tool. This project is not limited to one specific application, but designed to have a wide range of material processing applications and is expected to open up opportunities to be applied to a variety of problems in modern manufacturing. At a global level, it addresses the need for environmental sustainable surface modification techniques (for advance heat sensitive materials like carbon fibre reinforced polymer (CFRP), thin-films, polymer wafers) by providing an attractive alternative to current manufacturing techniques that use chemicals and abrasives. The use of LIDV technique will reduce the accumulation of harmful chemicals and abrasive grit in the environment, thereby enhancing the quality of life.

At national level, the output of the project has the potential to stimulate UK industries and facilitate job creations. The immediate beneficiaries of LIDV technology will be the industries using CFRP. Drawbacks associated with the traditional manufacturing process restrict the affordability and wider CFRP take-up within UK manufacturing industries. The outcome of the project will enable UK manufacturing industries to access state-of-the-art LIDV material processing techniques and will allow UK industries to be competitive in developing new products using CFRP. This will stimulate the entire market sector, will attract new investment and will provide a greater boost to the UK economy as a whole. Currently there are around 1600* companies involved in the UK CFRP sector supporting more than 130,000 people and producing revenue of around £1.1 billion. If the LIDV technology can lead to a growth of just 0.001%, it would generate over 100 extra jobs in the UK. The demand for CFRP composites in the UK is forecasted to grow at 17%* and introducing LIDV techniques (green manufacturing) will facilitate the UK composite sector to overcome the stringent environmental legislation on use of harmful chemicals.

The project has the potential to stimulate a wide range of spin-off applications (coating free shock peening; room temperature nano particle embedment; shock wave induced thin films transfer) thereby extending the advantages to a wide range of UK manufacturing industries and in particularly the small and medium scale enterprises (SMEs). For example, the existing laser shock peening (LSP) process is laborious and un-affordable to most SMEs. The proposed LIDV technology can produce shock pressure similar to the magnitude observed in traditional LSP with less number of steps and in a dry environment. This will make the LIDV based shock peening process affordable and within the reach of most UK SMEs. Apart from new job opportunities, this will increase the quality of UK products and subsequently the national growth. The proposed project will be an outstanding training opportunity for the PhD research students (one studentship fully funded by Loughborough University and potential for additional studentship from EPSRC Doctoral Training in Ultra Precision** and Manufacturing Technology Engineering Doctorate Centre***).

Historically, the UK is a market leader in Nd:YAG laser manufacturing, with around 20 companies and employing around 1800 highly skilled personals. The LIDV process will open up an entirely new market for nanosecond Nd:YAG lasers, which will strengthen the UK laser manufacturing sector and will enhance their global competitiveness.

*UK Composites Supply Chain Scoping Study, Department of Business, Innovation & Skills.
**Attached letter of support from University of Cambridge.
***Loughborough University and Manufacturing Technology Centre, Coventry are key partners in this centre.