DEVELOPMENT OF A VERSATILE RECYCLED COMPRESSION MOULDING COMPOUND MADE FROM UNCURED AEROSPACE PREPREG OFFCUTS

摘要

Aerospace composites manufacturers discard anywhere from 30-50% of their prepreg fabric during the ply-cutting phase of manufacturing. This waste is mainly attributed to nesting pattern inefficiencies caused by limited production schedules, fixed prepreg roll widths, and limited material out-life. By recovering uncured prepreg offcuts from the ply cutter and transforming them into a recycled prepreg moulding compound (rPMC), it may be possible to produce complex semi-structural components with applications in the aerospace, automotive, or recreational sporting industries. This approach, however, carries with it two major manufacturing challenges. The first is related to order-of-magnitude differences in autoclave and compression moulding resin system processing viscosities. Autoclave resins are tailored to exhibit high levels of percolation to ensure proper fibre bed impregnation, whereas compression moulding compounds are designed to deform in shear, so that transport of fibre and resin occurs simultaneously, resulting in complete mould cavity filling. Secondly, compression moulding compounds are cured in as few as 3-5 minutes to satisfy the production rates of a given industry, whereas autoclave curing of large aerospace components can frequently take as long as 8-12 hours. This paper introduces a recycling framework for compression moulding of uncured prepreg offcuts. The processing aspect of the framework is discussed in detail, where thermochemical resin characterization and 1-D flow-compaction trials are used to understand the impact that a resin's processing viscosity has on the nature and magnitude of prepreg flow. A recycling process map is then presented in which flow tailoring and cycle time customization is achieved by increasing the resin's initial degree-of-cure through staging.