Quentin Govignon

Characterisation of woven flax fibres reinforcements: Effect of the shear on the in-plane permeability

This paper describes a method to characterise the influence of in-plane shear on the permeability of fibrous preforms used in liquid composite moulding processes. An optical method for measuring the local shear variation of the woven textile is presented and used in conjunction with an in-plane permeability measurement system. Two flax fibre fabrics were tested and compared with a woven glass fibre fabric of similar architecture. The system presented here can be used either as a validation tool for permeability prediction models or to compile semi-empirical permeability models for the use in liquid composite moulding process simulation tools.

Experimental investigation into the post-filling stage of the resin infusion process

The resin infusion process has developed as a low-cost method to produce large composite parts in low to medium quantities. Although the process is conceptually simple, the effects of many of the processing parameters on the post-filling stage of the process are not well understood. Most manufacturers tend to develop their approach to infusion process through trial and error, and then adhere to their ‘secret recipe’ without knowledge of the effect of each parameter. This paper describes an experimental investigation of the controllable process parameters and their effect on the final laminate composition, by monitoring local fluid pressure and full field laminate thickness data through the filling and post-filling stages. From the understanding of the effect of each parameter, guidelines are drawn to help manufacturers to optimise their process. The effect of using a ‘brake’ between the part and the vent are evaluated, and the benefits of turning the inlet into a vent at the onset of post-filling are highlighted together with methods of gaining some control on the final laminate fibre volume fraction.

Efficient experimental characterisation of the permeability of fibrous textiles

Two experimental set-ups used to characterise the in-plane and through-thickness permeabilities of reinforcing textiles have been developed and are presented. Both the experimental testing and data processing techniques used have been selected to ensure that the characterisation is completed in an efficient and robust method, increasing the repeatability of tests while minimising user induced errors as well as the time and resources needed. A number of key results and outputs obtained are presented from tests carried out on a plain woven reinforcing textile with a range of number of layers and at different fibre volume fractions.

Resin infusion/liquid composite moulding (LCM) of advanced fibre-reinforced polymer (FRP)

Abstract: The term liquid composite moulding (LCM) encompasses a family of processes in which a dry fibrous reinforcement is impregnated by a liquid resin inside a sealed cavity. As the understanding and control of these processes improve, their field of application widens. LCM processes can be used as a replacement to decrease the environmental impact and improve the quality of composite parts made via traditional open-mould processes. they can also provide a cost-cutting alternative to prepreg techniques while maintaining a high part quality. This chapter describes the variety of processes blanketed under the class liquid composite moulding and the research advances in the monitoring and simulation of these processes. the subsequent section presents the current usage of LCM techniques in the field of civil engineering, including some case studies, before outlining some future trends and offering sources for further information.

Control of laminate quality for parts manufactured using the resin infusion process

Resin infusion is a manufacturing process used to produce fibre-reinforced thermo-set polymer components. This process is utilised in a range of industries such as aerospace, automotive, marine, rail and defense and is a cheaper method when compared to other closed mould or autoclave manufacturing methods, particularly as the size of the parts increases. In this study, wet compaction characteristics and behaviour of three glass fibre reinforcements were analysed, and 2D panels were manufactured with a selection of inlet and vent pressure combinations during both the filling and post-filling stages of the process to achieve control of the final fibre volume fractions. Reinforcement thickness and resin pressure were monitored throughout each experiment and the achieved fibre volume fractions were measured post-manufacture. Void content was analysed microscopically and related to the respective experimental parameters set. The compaction result fairly predicted the achieved fibre volume fraction of the manufactured part. The possibility of controlling the fibre volume fraction through control of the post-filling pressure was demonstrated. Even though there was a risk of increased void content with some post-filling configurations, the fibre volume fraction could still be controlled without creating voids with careful application of post-filling conditions.