Abstract
The paper presents a new modelling concept for describing the compressibility of toughened uncured prepregs over a wide range of processing conditions (i.e. automatic fibre deposition, hot debulking and pre-curing consolidation). The primary challenge of the work is to simulate the material response due complex flow and deformation mechanisms. This generation of prepreg systems exhibits both percolation (bleeding) flow typical for conventional thermosets, where the pressure gradient causes resin flow relative to the fibres, and shear (squeezing) flow typical for thermoplastics, where the laminate behaves as a highly viscous incompressible fluid. As a result, it holds features of both the systems: e.g. a convergence to a certain compaction limit at high temperatures and pressure levels and size/ply configuration-dependent material response. The modelling starts from micro-structural considerations, which give the foundation for an analytical model that assumes a transition from percolation to shear flow. It is shown that this model can capture the material behaviour very well. A hyper-viscoelastic material model is then constructed and implemented within the finite element package Abaqus/Standard. The model parameters are identified from an experimental programme and validated against compaction experiments over a wide range of load rates, temperatures and laminate configurations.
Highlights
The increasing use of composite material attracts attention to the idea of replacing the traditional experimental trial-and-error based methods with the optimisation of processing parameters through numerical simulations and virtual manufacturing
Consolidation is commonly understood as the processing step in which pressure is applied and plies are engaged in a full contact and inter- and intra-ply porosity is eliminated by means of compaction
Compaction experiments were performed on two toughened epoxy prepreg systems: IM7-8552 and IMAM21 under processing conditions consistent with automatic fibre deposition; hot debulking and pre-curing consolidation
Summary
The increasing use of composite material attracts attention to the idea of replacing the traditional (costly) experimental trial-and-error based methods with the optimisation of processing parameters through numerical simulations and virtual manufacturing. For example Hubert and Poursartip (2001), testing toughened and low viscosity prepregs on curved tools with bleed and non-bleed bagging conditions, clearly demonstrated that both squeezing and percolation flows can act concurrently Neglecting one or another may lead to significant error in thickness estimation. From the analysis of the pore volume fraction (Nixon-Pearson et al, 2015) this can be limited to 5% The application of this prepreg consolidation model is for thickness evolution in debulking and autoclave processes where the in-plane movements of the material are relatively small compared to forming processes. The proposed model was further implemented in the implicit finite element (FE) software Abaqus/Standard in the form of a hyper-viscoelastic model using the thermodynamical framework proposed by Limbert and Middleton (2004)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
