REUSE STRATEGIES FOR CARBON FIBER-EPOXY PREPREG SCRAP

摘要

Composites manufacturing using prepregs results in the generation of scrap arising from several sources, such as edge and trim waste from ply cutting, cut-off ends of tow and tape, over-long out times, and expired material. While established and commercialized fiber reclamation techniques exist to handle end-of-life cured composite parts (i.e. recycling), there are no commercially viable techniques to re-use the large volumes of uncured or partially cured prepreg scrap other than disposing it in landfills. This poses an environmental concern and incurs substantial cost. Waste disposal fees, that increase if the waste is classified as hazardous, add to overall manufacturing costs. These concerns are certain to grow, given the increasing use of composite prepreg materials in aircraft structures and the large projected demand for these new composites-intensive airplanes. This study focuses on reusing prepreg scrap for potential applications, including shipping containers, composite tooling, sporting goods, consumer goods, and automotive parts (i.e. upcycling). The process is demonstrated using an out-of-autoclave (OoA) carbon fiber/epoxy prepreg. Uncured or partially cured prepreg scrap is first reduced to chip form that may be used as-is or further processed into roll form, from which plies are cut. These various material forms can then be consolidated through traditional processes such as hot pressing, compression molding, and vacuum bagging. In the initial phase of the study, the microstructure, void content, and mechanical properties of laminates made from reused prepreg scrap chips are evaluated and compared with virgin prepreg (i.e. baseline). Several parameters are considered, such as chip size and geometry, fiber bed architecture, out-time and tack, consolidation pressure, temperature ramp rate, and boundary confinement including hybrid constructions of scrap chips and continuous prepreg plies. In addition to acceptable tensile and compressive strength and moduli retention, the laminates possess a visually pleasing surface texture. Strategies to scale up and automate the production of consistently-sized prepreg scrap chips and the production of reused scrap chip based rolls are presented. The outcome of this work provides a sustainable and environmentally-friendly solution to the growing prepreg scrap waste problem in the composites industry as well as a commercial opportunity for the industry to recover some original material cost. Moreover, the newly developed scrap-based product forms could lead to several new business opportunities.