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Analytical formulations for the pressure profile in rectilinear and radial flow vacuum infusion (VI) processes are developed. The coupled pressure formulations are solved using an iterative numerical procedure. As the formulations are coupled, reinforcement specific solutions need to be derived. The VI process is also modelled using a numerical flow simulation tool, using a previously reported approach. In addition, analytical formulations for fill times in the rectilinear and radial flow VI processes are developed. It is found that with increasing reinforcement compliance, the analytical VI pressure profile diverges from the resin transfer moulding (RTM) pressure profile. Results from numerical flow simulations show a similar behaviour. The error level in the numerical results of VI pressure solution depends on the reinforcement compliance. The fill times ratio, between equivalent RTM and VI processes, remains constant for rectilinear and radial flow processes. This allows one to use RTM flow simulation tools to model rectilinear and radial flow VI processes without any major modifications.

Textile permeability in general shows a high variance. The present work describes a method to model textile variability at the mesoscopic scale based on a generalised textile model. Inhomogeneities were introduced into the textile structure by randomly moving the tow paths at the cross-overs according to a given normal distribution. The effects of various factors on the evaluated permeability variation were explored and demonstrated, using non-crimp fabric and plain weave models. Fabric architecture was shown to be important in that it imposed a limit to the degree of variation of the tows. A linear relationship can be deduced for the relative variation of permeability as a function of the relative variation of fibre volume fraction, which links the predicted and measured values. When utilising predicted mesoscopic permeability values in macroscopic analyses, the domain size of the mesoscale model has to be related to the element size of the macroscopic analyses.

A balanced twill weave commingled fabric was consolidated by an isothermal vacuum forming process. Samples were tested in three point bending and the void content was measured to validate a consolidation model that predicts void content as a function of pressure, time at pressure, and temperature. Sensitivity studies revealed the effect of two parameters - the number of fibre agglomerations and the empirical permeability parameter, used to fit the consolidation model. A microscope image analysis technique was used to investigate the evolution of the microstructure during consolidation and to quantify levels of void content. These measurements were correlated with the mechanical properties of laminates consolidated for a range of times at pressure. It was found that a void content of 10% decreases flexural strength by 50%.

The impact properties of commingled E-glass-polypropylene composites with varying fibre architectures have been investigated. The fabric structures include balanced and unbalanced twill weaves and a three-dimensional woven fabric. Comparative data for glass mat thermoplastics are included and additional comparisons with crossply continuous filament tape laminates are also made. All the materials were processed into flat panels via non-isothermal compression moulding. First, voidage was correlated with processing parameters to produce well consolidated laminates. Mechanical tests included tensile, flexural, and interlaminar shear. Impact tests include Charpy and falling weight; the latter ranged from 15 J to full penetration and were followed by IR thermography and microscopy to determine the extent of damage areas. The results demonstrate the evolution of damage with increasing impact energies and the mode of impact damage propagation for the different fibre architectures.

This paper presents an overview of a method of predicting the permeability of textile preforms. The equations involved in the calculation of the pressure distribution and flow field resulting from the imposition of a pressure gradient between two opposed faces of a porous domain are outlined. The presentation is for a two-dimensional cross-section but the method applies to a full three-dimensional domain featuring porous tows and free channels defined between the tows. The mathematical treatment was kept as simple as possible in order to gain speed and improve productivity. Fast calculation methods allow the prediction of the variation of permeability over a preform, providing valuable information to the simulation of the filling. The method does take into account the heterogeneity of the preform, the architecture of the textiles, as well as the porosity and shape of the tows.

A geometric textile modelling package (modeller) is being developed, which forms the basis for a number of software tools predicting the processing properties of textile reinforcements and the final properties of composite parts. The modeller can provide interlacing patterns representing any textile reinforcement in a simple, universal format. In this paper the general concept of the modeller is presented and examples are provided for woven textiles and noncrimp textiles assembled by a warp knitted stitch. The modeller and the predictive tools are modular. The main advantage of this is that tools for the prediction ofthe reinforcement properties can accept any geometricdefinition, regardless of the textile type, provided that the definitions and models are expressed in the required format. The tools also have the capacity to assess properties such as permeability or behaviour in compaction and shear, for preforms containing textiles of different types.

The effects of deformation of the reinforcement during manufacture on the elastic properties of textile composite components have been investigated. Fibre reorientation and changes in the fibre volume fraction are considered as the dominant mechanisms affecting mechanical properties. A model is presented for the prediction of the component's elastic performance. Fibre orientations may be predicted or measured; methods for each approach are outlined briefly. The component geometry is described using a finite element mesh, and for every element fibre orientations are used to determine fibre volume fraction. Elastic properties are calculated for each element and an input deck for structural analysis using the Abaqus/Standard™ finite element code is produced. Experimental data for tensile tests conducted on angle ply laminate specimens at a range of ply angles are presented; predictions show good agreement with these data. Predicted results for a jet engine nose cone subjected to a pinch loading also...

In this paper, the shear properties of a number of woven and non-crimp (multiaxial warp knit) fabrics are analysed. These are shown to be related to the fibre architecture and, for non-crimp fabrics, the pattern and orientation of the stitching thread. A detailed geometric model has been developed for the deformation of woven fabrics during in plane shear, and this is used as a basis for a mechanical analysis to predict shear compliance. This model incorporates intertow friction, tow compaction, and in plane (membrane) tension. Finally an iterative model for fabric forming is described, based on fabric shear energy obtained either from the mechanical model or from experimental measurements. This is validated for a hemisphere and an automotive transmission tunnel and is shown to offer greater accuracy than the traditional geometric mapping, while associated computation times are at least an order of magnitude lower than those associated with non-linear finite element analysis.