Richard Crossley

Furan matrix and flax fibre as a sustainable renewable composite: Mechanical and fire-resistant properties in comparison to phenol, epoxy and polyester

Due to environmental and fossil fuel supply concerns, polyfurfuryl alcohol or ‘furan’ resin has recently gained attention as a renewable alternative thermoset resin with reduced CO2 emissions in comparison to the existing petrochemical-based systems. When combined with natural flax fibres, it offers the potential to produce a fully bio-derived sustainable composite with structural mechanical capabilities and fire-resistant properties. In this study, the mechanical properties of furan flax and E-glass fibre laminates are characterised and directly compared to polyester, epoxy and phenolic laminates produced using identical reinforcing fibres and methods. In addition, the acidity and fire-resistant properties are also compared. Furan resin E-glass laminates were found to have mechanical properties comparable to existing resin systems with excellent fire-resistant properties, which are equal to that of phenolic and exceeding polyester and epoxy performance. However, both phenolic and furan flax laminates were found to give reduced mechanical performance in comparison to polyester and epoxy. This reduction in strength was attributed mostly to micro voids surrounding elementary flax fibres believed to be the result of post-cured fibre shrinkage due to moisture uptake.

Experimental determination and control of prepreg tack for automated manufacture

Abstract The automated tape laying (ATL) process has been examined and found to be sensitive to tack and stiffness properties of the prepreg material being laid. A comparison of existing aerospace and newly developed ATL prepreg tapes has revealed significant differences in tack response to temperature and feedrate. Examination of constituent resin rheology has found that tack, and the two observed failure modes, are somewhat dependent upon viscoelastic stiffness. Observation of temperature and feedrate response revealed a time–temperature superposition relationship. The Williams–Landel–Ferry equation was utilised to make predictions of the temperature response based on the feedrate response. Tack levels were stabilised over the feedrate range by making temperature adjustments. Results from the peel test, where mould conditions at lay-up were recreated, were found transferable to the ATL, where a suitable lay-up feedrate under ambient conditions was predicted.

Wind Turbine Blade Design Review

A detailed review of the current state-of-art for wind turbine blade design is presented, including theoretical maximum efficiency, propulsion, practical efficiency, HAWT blade design, and blade loads. The review provides a complete picture of wind turbine blade design and shows the dominance of modern turbines almost exclusive use of horizontal axis rotors. The aerodynamic design principles for a modern wind turbine blade are detailed, including blade plan shape/quantity, aerofoil selection and optimal attack angles. A detailed review of design loads on wind turbine blades is offered, describing aerodynamic, gravitational, centrifugal, gyroscopic and operational conditions.

Technology review of thermal forming techniques for use in composite component manufacture

There is a growing demand for composites to be utilised in the production of large-scale components within the aerospace industry. In particular the demand to increase production rates indicates that traditional manual methods are no longer sufficient, and automated solutions must be sought. This typically leads to automated forming processes where there are a limited number of effective options. The need for forming typically arises from the inability of layup methods to produce complex geometries of structural components. This paper reviews the current state of the art in automated forming processes, their limitations and variables that affect performance in the production of large scale components. In particular the paper will focus on the application of force and heat within secondary forming processes. It will then review the effects of these variables against the structure of the required composite component and identify viability of the technology. Through this, an understanding of the key criteria involved in the forming of composite aerospace components can be utilised to better inform improved manufacturing processes and capabilities.