Poromechanical Modeling of Composites Manufacturing

Doctoral thesis, 2015

Fibre reinforced composite materials are used extensively in today's industry. On one hand, the low-weight feature of this kind of material gives important advantages such as lower fuel consumption and lower amount of CO2 emissions. On the other hand, corrosion and high temperature resistance has made them suitable for different type of environments. Composite materials are also assumed to grow significantly in automotive industry in near future. In these perspectives, especial attention has risen up towards development of advanced manufacturing technologies where higher production rate, lower cost and lower environmental issues are desired. To achieve this goal, numerical simulations and CAE tools are employed to predict the behavior of manufacturing methods with respect to the process optimization and the product properties. The focus of this research thesis is toward development of a framework for holistic modeling of fiber reinforced composites manufacturing. The manufacturing process can be considered as a fluid filled porous material, which can be described, on macro scale as well as micro scale, by the Theory of Porous Media (TPM). The TPM has been further enhanced by introducing the concept of phase compressibility of the biphasic mixture of solid and fluid, in order to describe the physical sub-processes happening in different scale. The model of the considered problem is then put forward to be solved by Finite Element Method (FEM). In the discretization of the numerical domain a quadratic six-node triangular element is used and a staggered solution procedure is chosen to solve the highly coupled problem in a finite strain regime. The most important challenges, that the numerical solution procedure is able to capture, are (1) modeling the compressible volumetrically-deformable fiber preform and the shape of membrane due to the different considered loading situations (2) the dual scale resin flow motion through the fibrous preform and the compaction of individual plies (3) deformation dependent permeability models (4) the free surface problem when the flow is moving with respect to a flow front velocity into the vacuum zone of the porous material. The framework that is developed here is capable of simulating different manufacturing processes based on the chosen initial conditions, boundary conditions and material parameters. Liquid Composite Molding (LCM), Liquid Resin Infusion (LRI), Resin Transfer Molding (RTM), Out of Autoclave (OoA), press forming prepregs, Engineering Vacuum Channels (EvaC) and similar manufacturing methods are some examples of the processes that have been simulated.