James is currently part of the Composite Materials Research Group at the University of British Columbia. The goal of his research is to establish a scientific understanding of the processes that lead to the formation of voids in carbon-fiber parts produced using out-of-autoclave pre-preg manufacturing processes. These manufacturing processes have the potential to dramatically reduce the cost of producing high quality composite parts.
Carbon fiber parts are manufactured by combining carbon fibers (which are extremely strong and stiff) with a liquid polymer resin such as epoxy. The polymer is then cured (usually by heating) to produce a solid carbon fiber reinforced polymer (CFRP) material. The carbon fibers act as the reinforcement, giving the material high strength and stiffness. The polymer acts as the matrix, which transfer the loads to the fibers, bind them together, and protect them from the environment. The resulting composite material combines the most desirable properties of both materials: it is extremely strong and stiff, but also lightweight and durable. This combination of properties has led to the adoption of CFRP in many industries, especially aerospace where high strength and light weight translate into significant fuel savings.
The majority of composite aerospace structures today are cured in a pressurized oven, or autoclave; however, because of the high cost of purchasing and operating an autoclave there has been much interest in methods of manufacturing carbon fiber parts without an autoclave. Currently, the major obstacle to this is the potential for forming small bubbles or voids in the material. In an autoclave manufacturing process the high pressure in the autoclave (around 6 to 7 times atmospheric pressure) forces any bubbles, water vapor or other void-forming substances to dissolve into the polymer resin so they cannot form voids during the curing process. In out-of-autoclave manufacturing processes, parts are usually cured under pressures of only one atmosphere or less, and so void-forming substances tend to become gas bubbles and form voids.
James' research investigates the relationship between the amount of voids in the final part and the processing conditions. These include factors like the size of the part, environmental humidity, the vacuum level achieved and the time the part spends under the vacuum bag. As the processes leading to void formation are better understood, it will be possible to predict what conditions are necessary to produce a void-free part. This will enable parts to be produced to the quality standards of autoclave processes, but at the lower cost of an out-of-autoclave process.