Liquid Composite Molding Processes Research Articles

Net-Shape Preform Manufacture using Automated Fibre Placement

Liquid composite moulding processes such as resin transfer moulding (RTM) are becoming increasingly popular for a range of commercial applications. The major barrier to their more widespread use is the lack of an efficient method for the manufacture of reinforcement preforms. To address this problem, an automated fibre placement facility is under development, capable of laying either random or aligned fibres to produce net-shape preforms. This has been applied to a number of components including a load bearing flange used in marine applications and an aviation propeller blade.

Processing and mechanical properties of bi-directional preforms for liquid composite moulding

Abstract The design and manufacture of fibre preforms for structural parts remains the major technical challenge in liquid composite moulding processes such as resin transfer moulding and structural reaction injection moulding. This paper sets out to identify new methods for preform design based upon fibre architecture in 2.5-dimensional preforms via a drape analysis. The predicted fibre geometry is related to models for permeability and elastic properties to generate property distributions over the part. These may then be used within finite element analyses to predict mould filling and structural performance. Experimental results are presented which include fibre distribution, in-plane permeability, elastic properties and structural tests. The integration of the stages within a design framework is discussed.

Glass fibre sizing/matrix interphase formation in liquid composite moulding: effects on fibre/matrix adhesion and mechanical properties

The glass fibre sizing/matrix interactions in a liquid composite moulding environment have been investigated to develop an understanding of the effect of wetting between sized fibre surfaces and the reacting liquid matrix, the structure of the resulting interphase and its effect on fibre/matrix adhesion and composite properties. The overall research objectives in this programme are to develop an experimental protocol for measurement of the key wetting parameters of the fibre and matrix; to quantify the effect of wetting on the mechanical properties of the composites formed by liquid composite moulding; and to formulate a time-, temperature- and geometry-dependent model of the liquid composite moulding process which incorporates the surface properties of the fibre, its finish and the reactive polymer matrix. Results are presented for a series of sized glass fibres consisting of incompatible and compatible sizings, studied with a reacting vinyl ester matrix system. Surface free energy analysis was conducted to characterize the fibre surfaces. Axial and transverse wicking rates were measured to quantify the change in total surface free energy of the fibre/matrix systems. The sizing surface free energy and its solubility in the matrix strongly affected the fibre/matrix interphase formation and consequently the fibre/matrix adhesion and composite shear and flexural strengths.