Identifying root causes and process control solutions for print-through phenomenon in thin open-moulded composite laminates

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Fibre-reinforced composite materials are becoming increasingly promising as the material of today and the future in several products that are used on daily basis, from car/bicycle bodies to house appliances, among several other applications. The world market value of end-use products manufactured from composites was reported to be $55.6 billion in 2011-2012, with the North American composites industry accelerating at approximately 9%. A major focus and interest in this field is the development of value-added manufacturing processes that can further advance capabilities of these promising materials. The quality of final composite products, however, is closely linked to the accuracy of processing parameters applied during their manufacturing. Glass fibre reinforced plastics (GFRPs) are today the most common type of composites used in products fabricated through open moulding techniques, particularly since they offer low capital costs when compared to, e.g., carbon fiber composites. One of the main metrics for quantifying the quality of a GFRP product is its surface finish. Inadequate choice of processing parameters can cause GFRP surface defects such as print-through, blisters, orange peel, cracking, and glossiness. Focusing on the print-through phenomenon (PTP) as one of the main current challenges for composites manufacturers, this project aims to employ a systematic experimental-statistical approach to identify main processing factors that contribute to the generation of this defect. A case study in the recreation sector, mainly GFRP RV sub-components manufactured by a composite manufacturer in B.C., Canada, using the chopped fibre spray-up technique has been considered. The main statistical parameters to study include: polymer matrix cure kinetics including temperature and humidity effects in summer versus winter conditions, moulding time, and post-de-moulding conditions. New knowledge and original best-practice guidelines are expected from this research as to how manage the PTP defect during manufacturing of GFRP parts, which can be of benefit to other Canadian composite industries in the long term.