A consolidation process model for film stacking glass/PPS laminates

The applied pressure, processing temperature and holding time influence the\ud consolidation of thermoplastic laminates. A model to optimise the processing\ud parameters is proposed. The influence of heating rate, processing temperature and pressure is investigated. Short textile impregnation times, in the order of seconds, are predicted. The model is validated in an experimental programme

Towards a process simulation tool for the laseer assisted tape placement process

A combined optical and thermal model for the laser assisted tape placement process is presented. The optical model adopts a ray tracing procedure, based on the Fresnel equations, to predict the incident heat flux on the tape and substrate near the nip-point. The heat flux distribution is subsequently used in a one-dimensional thermal model to predict the temperature distribution in the tape and substrate. The results demonstrate that for small incident laser angles a part of the laser light is reflected at the surface, which significantly influences the temperature distribution in the nip-point. The presented model allows, with a weld strength and consolidation model, optimization of the processing parameters

Development of a multigrid finite difference solver for benchmark permeability analysis

A finite difference solver, dedicated to flow around fibre architectures is currently being developed. The complexity of the internal geometry of textile reinforcements results in extreme computation times, or inaccurate solutions. A compromise between the two is found by implementing a multigrid algorithm and analytical solutions at the coarsest level of discretisation. Hence, the computational load of the solver is drastically reduced.\ud This paper discusses the main features of the 3D multigrid algorithm implemented as well as the implementation of the analytical solution in the finite difference scheme. The first tests of the solver on the permeability benchmark lithographic reference geometry are discussed.\ud Several tests were performed to assess the accuracy and the reduction in calculation time. The methods prove to be both accurate and efficient. However, the code is developed in Matlab© and hence is relatively slow. A C++ code is currently under development to achieve acceptable calculation times

Textile impregnation with thermoplastic resin - models and application

One of the key issues of the development of cost-effective thermoplastic composites for the aerospace industry is the process quality control. A complete, void free impregnation of the textile reinforcement by the thermoplastic resin is an important measure of the quality of composites. The introduction of new, more thermal resistant and tougher polymers is accompanied by a large number of trial and error cycli to optimise the production process, since the polymer grade strongly influences the processing conditions. Therefore, a study on the impregnation is performed. Thermoplastic manufacturing processes are often based on pressure driven, transverse impregnation, that can be described as a transient, non-isothermal flow of a non-Newtonian fluid, where a dual scale porosity is assumed for the reinforcement's internal geometry. Meso- and micro scale models of isothermal flow revealed a limited sensitivity to the process conditions at the bundle scale for high pressure processes such as plate pressing, with an increasing sensitivity for lower pressures as apply for autoclave processes. The process conditions are significant for the quality of impregnation at filament scale. Specific combinations of pressure, viscosity and bundle compressibility can lead to void formation inside the bundles, as confirmed by microscopic analysis. The methodology developed has been translated to a ready-to-use design tool for the implementation of new polymers

A state-rate model for the transient wall slip effects in ply-ply friction of UD C/PAEK tapes in melt

Ply-ply slippage is one of the key deformation mechanisms occurring during hot press-forming of thermoplastic composite laminates. Advanced forming simulations, required for defect-free manufacturing, rely on accurate constitutive models for these deformation mechanisms. In this work, we propose a relative simple, yet accurate, transient model to describe the start-up friction response of UD C/PAEK tapes. The model combines a White–Metzner viscoelastic fluid with a state-rate model for the evolution of wall slip near the fiber–matrix interface, describing the disentanglement of surface polymer chains followed by the settlement of these chains in a new equilibrium state. This allows prediction of the stress growth at start-up and the transition from peak to steady-state friction, from smooth to sharp with increasing sliding rate, as well as the magnitude of the peak and steady-state friction. We obtained a good correlation between the modeled and measured friction response for different sliding rates

Modeling anisotropic friction in triaxial overbraiding simulations

Triaxial overbraiding is a highly intricate textile manufacturing process that involves interlacing yarns in three directions, enhancing reinforcement of the final composite compared to biaxial braids. Predictive process simulation is a cost-effective approach to optimizing the manufacturing process. Previous research on biaxial overbraiding simulations indicates that yarn-yarn friction has a significant effect on the braid angle and convergence zone length. This study presents an extended yarn interaction model; it utilizes a fast frontal approach and a Eulerian on Lagrangian method to simulate the complex interlacing of multiple yarns in triaxial overbraiding, including yarn-yarn and yarn-ring friction. Experiments were conducted to evaluate the effect of UD yarn tension on the convergence zone length and braid angle, and to validate the simulations. The model validation shows that a recently proposed anisotropic yarn-yarn friction model predicts braid angle more accurately than an isotropic friction model