Resin transfer moulding: Novel fabrics and tow placement techniques in highly loaded carbon fibre composite aircraft spars

A BAE Systems /UK EPSRC funded project Flaviir, is investigating the design and manufacture of low cost carbon fibre composite airframe structures. Novel binder coated unidirectional fibre tapes and tows were developed to enable the design of optimised primary structures. The RTM technique was applied to mould net shape sections of spar components. Various designs of wing attachment lugs were manufactured with a range of reinforcement materials, including non crimp fabric, novel binder coated tapes and conventional unidirectional prepreg. Alongside these, a novel technique termed optimised tow lay up (OTL) was used to reduce the weight. Binder coated carbon fibre tow is placed around the structure in the principal stress directions to increase both bearing strength and overall component stiffness. The novel materials, manufacturing technique and initial element test results are presented

Effect of water immersion on the interlaminar and flexural performance of low cost liquid resin infused carbon fabric composites

This study investigates some potential benefits of using non-epoxy matrices in carbon fibre composites, targeting specific marine and wind energy applications. Water uptake during and after immersion for up to 28 days in deionised water at 40°C, and the effects of such conditioning on the interlaminar shear and flexural performance of the composites with isophthalic polyester, vinyl ester and urethane acrylate matrices were compared to those of equivalent composites impregnated with three grades of epoxy resin. Results demonstrated that, although the epoxy systems perform equally or better than the alternative resins in the dry state, they are also more sensitive to property degradation due to water ingress. The relatively lower water absorption and subsequent limited reduction in performance of vinyl ester and urethane acrylate composites is sufficiently promising to justify further stud

Exploring mechanical property balance in tufted carbon fabric/epoxy composites.

The paper details the manufacturing processes involved in the preparation of through-the-thickness reinforced composites via the ‘dry preform–tufting–liquid resin injection’ route. Samples for mechanical testing were prepared by tufting a 5 harness satin weave carbon fabric in a 3 mm × 3 mm square pitch configuration with a commercial glass or carbon tufting thread, infusing the reinforced preforms with liquid epoxy resin and curing them under moderate pressure. The glass thread reinforcement increases the compression-after-impact strength of a 3.3 mm thick carbon fabric laminate by 25%. The accompanying drop- downs in static tensile modulus and strength of the same tufted laminate are below 10%. The presence of tufts is also shown to result in a significant increase in the delamination crack growth resistance of tufted double-cantilever beam specimens and has been quantified for the case of a 6 mm thick tufted carbon non-crimped fabric (NCF)/epoxy

Effect of tufting on the mechanical behaviour of carbon fabric/epoxy composites

This work draws some early baselines on the in-plane/out-of-plane properties balance in a 5HS woven carbon fabric/epoxy composite reinforced by tufting and resin injected by resin transfer moulding technique. Details of the manufacturing processes involved in the preparation of such through-the-thickness reinforced composites are presented together with analysis of the mesostructure of tufted specimens. Preforms were reinforced locally with a commercial glass or carbon fibre thread. The tufts were inserted in square arrangement with a KSL tufting tool interfaced to a 6 axis computer controlled robot arm from Kawasaki. The presence of tufts improved significantly the delamination resistance, assessed by testing double cantilever beam coupons in mode I loading configuration. In-plane tension and compression after im¬pact (CAI) tests revealed that the reinforcement resulted in a considerable increase in the post-impact residual strength value, with an accompanying drop down in static tensile modulus and strength of less than 10%. In addition to the standard coupons for the determination of the quasi-static mechanical properties, some cured miniature specimens containing a limited number of tufts were also prepared. These were tested in both uniaxial pull-out and in a mode II configuration in order to measure the bridg¬ing actions of the tufts and to determine the micromechanical failure mechanisms. The obtained crack bridging laws were used for calibrating a simple analytical model of the mechanical behaviour of a single tuft within the composite. The tufting technology was applied to an innovative concept that aims to adopt the tufting threads as a carrier for resin modifiers. For this purpose a single-filament and a multi-filament thermoplastic prototype threads were used. These threads are not intended to modify the composite fibre architecture but are expected to dissolve into and react with the host matrix upon cure. The outcome of mode I delamination and CAI tests conducted on woven preforms reinforced with such `soluble' threads are presented and discussed

DEVELOPMENT OF A NEW CLASS OF HYBRID REINFORCED THERMOPLASTIC COMPOSITES BASED ON NANOCLAYS AND WOVEN GLASS FIBRES

In this research was prepared and evaluated a novel laminate in which a traditional Glass Fibre (GF) Mat reinforcement was used to improve the physical and mechanical behaviour of a Polypropylene (PP) nanocomposite (NCP), based upon organophilic layered silicates (NC) and Maleic Anhydride grafted PP (PPgMA) as compatibilizer. The objectives of this investigation were: - to provide a general concept for manufacturing first polymer nanocomposites by direct intercalation during conventional twin screw extrusion-compounding process, and then nanocomposite laminates by pressure moulding; - to qualitatively and quantitatively estimate both the assessed level of particles dispersion and the influence of nano-fillers and of glass reinforcement on the material mechanical behaviour. The PP based nanocomposite was analysed by burn off test, differential scanning calorimetry and X ray diffraction. Significant micrographs were taken by optical, scanning electron and focused ion beam microscopy both on nanocomposite samples and on laminates. The NCP mechanical behaviour was evaluated by dynamic mechanical thermal analysis and tensile testing. The latter was used to estimate the mechanical properties of the final laminate as well. The final material can be considered three times ‘hybrid’: halfway organic and inorganic, halfway conventional composite and exfoliated, halfway laminated and nanocomposite material. However, to avoid misunderstanding, it is worth to note that, in this work, as ‘hybrid’ is intended the laminate matrix (i.e. PP-NC-PPgMA composite), like in the greatest part of the literature on this topic