We present a plane strain finite element model for simulation of the development of process-induced deformation during autoclave processing of complex-shaped composite structures. A “cure-hardening, instantaneously linear elastic” constitutive model is employed to represent the mechanical behaviour of the composite matrix resin, and micromechanics models are used to determine composite ply mechanical properties and behaviour, including thermal expansion and cure-shrinkage. Structures with multiple composite and non-composite components can be simulated through the use of such strategies as adaptive time-stepping and incorporation of multiple composite plies into each finite element. The effect of process tooling can also be directly modelled through simulation of tool/part interfaces and post-processing tool removal. Integration of the residual deformation model with models for heat transfer and resin cure and resin flow permits analysis of all major identified sources of process-induced deformation during the autoclave process. Model application is demonstrated through prediction of process-induced deformation of a number of variations of a simple L-shaped laminate. The model is shown to provide accurate predictions of both spring-back angle and warped shape of the final part.
A numerical flow-compaction model is developed and implemented in a finite element code to simulate the multiple physical phenomena involved during the autoclave processing of fibre-reinforced composite laminates. The model is based on the effective stress formulation coupled with a Darcian flow theory. A Galerkin approach is employed to discretize the weak form of the governing equations. The current formulation successfully describes the compaction behaviour of complex shape laminates caused by flow of the resin. A parametric study is performed to investigate the effect of the material properties on the compaction of angle-shaped composite laminates. It is found that the fibre bed shear modulus significantly affects the compaction behaviour in the corner sections of curved laminates while the resin viscosity and fibre bed permeability affect the compaction rate of the laminate. Figure 2. Laminate representative volume and plane strain composite elementformulation used for the flow-compaction module. A parametric study of the more important parameters for the flow-compaction model will also be presented.
MODEL DEVELOPMENT
AssumptionsPerforming the analysis on only a 2-D section (Figure 2) is believed to be adequate and appropriate for many composite structures, as at least one dimension is usually much larger than the other two. Gradients in this third direction are correspondingly small and can safely be Figure 7. Comparison between predictions by COMPRO versus LAMCURE for a 1-D flow consolidation: (a) boundary conditions for the 20 elements mesh; (b) predicted variation of vertical displacement at the top of the model (z"h) for both low and high flow systems 12 P. HUBERT, R. VAZIRI AND A. POURSARTIP
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