Cure-dependent thermo-chemical modelling and analysis of the manufacturing process of an aircraft composite frame

Abstract

This study contributes to the understanding of the mechanism behind thermo chemical aspects related to the resin transfer moulding manufacturing process of a composite part. The aim is to comprehend the phenomena, to identify related parameters and to get knowledge-based methods for the process development. Therefore, the first part of this study is an experimental study about the behaviour of material properties during the manufacturing process of the single component and the composite. It concludes with constitutive equations for single-process parameters and their associated homogenisation approach for the composite properties. During the manufacturing process, material values of the matrix are changing and influenced by a high number of effects. In the second part, a simulation strategy is been derived. This developed material model integrates a dependency of the time–temperature–polymerisation and fibre volume content. The model is validated in a test case of a manufacturing process of an aircraft component, a fuselage frame.

Viscoelastic model with complex rheological behavior (VisCoR): incremental formulation

“…This approximation gives much faster convergence in simulations than assuming it constant. According to Table 3, where the peak values of the calculated stress are shown, taking Dt k ¼ 0:1 sec in the VisCoR model leads to higher accuracy than Dt k ¼ 0:01 sec used in the formulation in [8,10,21] where the shift factor value in the beginning of the increment is used: the number of time steps can be significantly reduced using the present formulation. Most of the published incremental procedures are formulated for constant time step Dt k ¼ Dt (except from Zocher's model [9], which is formulated for a constant reduced time step Dw k ¼ Dw).…”

“…In fact, this model is "pseudo-viscoelastic"; the behavior in the rubbery state is assumed to have instant stress relaxation whereas in the glassy state there is no relaxation at all. Due to its simple implementation and relatively inexpensive computation costs, it has been widely used in various commercial tools for process simulations of industrial relevance [10][11][12][13].…”

Fabrication induced spring-back in thermosetting woven composite parts with variable thickness

“…Hygroscopic loads contributing to stress formation were also included in model [19]. Simulation of stresses and their corresponding change in the geometry was predicted using different FE models for different shapes to avoid the huge cost of hit and trail tool correction [20–26]. Modeling of shape distortions while considering the fabric drape and fibers reorientation was done [27,28].…”

Thermo-Chemical Analysis of the Cure Process of Thick Polymer Composite Structures for Industrial Applications

“…The use of non-optimum temperaturetime cure cycle can lead to overheating of the inner layers of the product material, degradation of the matrix resin and associated porosity increase, the accumulation of residual stresses which decrease the strength properties of the material, the deviation degree of crosslinking of the polymer matrix from the optimum, the distortion and deviation from the desired finished product geometry, etc. To eliminate these shortcomings and to ensure low cost and high quality products, as well as to increase the intensity of the process it is necessary to use the optimal temperaturetime cure cycle [3][4][5][6][7][8][9]. Thus, the main tasks that must be solved in determining the optimal cure cycle of thick polymer composite structures are as follows:…”

“…The modern methods of designing the optimal cure cycles of polymer composites are based on the use of mathematical models. They consist in the formulation and numerical solution of the extreme problem of minimizing some optimality criterion, ensuring the creation of high-quality finished product in minimal time with minimal residual stress [3][4][5][6][7]. By means of this concept it is possible to determine the cure cycles of the polymer composite products for any geometric sizes and shapes.…”