PRECARBI - Materials, Process and CAE Tools Developments for Pre-impregnated Carbon Binder Yarn Preform Composites
Overview
Background & policy context:
Composites are the material of choice for many advanced aircraft structural applications (A380 - 28% and Boeing 787 - 50% content) and have proven weight/performance superiority over metals. The critical issues today are performance improvements, development of faster, more cost effective manufacturing and simulation tools to optimise their manufacture and design.
Today manufacture of advanced composites uses either layers of pre-impregnated plies (prepregs) to form a laminate, or resin infusion of dry textiles (Liquid Composite Moulding LCM). Prepreg composites give superior mechanical properties due to toughened resins well dispersed in carefully controlled fabric architecture, but suffer from high material costs, limited shape-ability, complex/expensive manufacturing and limited shelf life.
Objectives:
LCM technologies can overcome many limitations, but must use low viscosity resins for infusion and suffer from fibre misalignments due to textile patterns, both of which lead to poorer mechanical performance, intolerable for many structural aircraft applications. The PreCarBi project set out to develop new materials (carbon fibres and liquid resins) as well as supporting technologies, already proven on a laboratory scale, that bring together prepreg and LCM technologies to combine the advantages of each.
Methodology:
Essentially pre-impregnated carbon fibres with a polymer binder formulation were developed for LCM and tow placement processes. Activation (e.g. heat, microwave and ultrasound) allows binder yarns to be (repeatedly) shaped prior to resin infusion. The binder yarns enhance mechanical properties, due to their formulation and ability to eliminate fibre waviness; also, they have indefinite shelf life, improve pre-form handling/trimming and drape-ability.
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