Multiscale Finite-Element-Simulation of the load carrying behaviour of fibre composite structures

• Applicant: Professor Dr.-Ing. Friedrich Gruttmann
• Subject Area: Mechanics ; Applied Mechanics, Statics and Dynamics
• Term: from 2013 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 233603725

The superior goal of the project is the computation of bearing loads for laminated fiber reinforced polymer structures on two scales. The model which has to be developed will be tested and evaluated by means of practical problems with appearing specialties. These are intersections of structural parts, corner arcs e.g. at a transition of a web to a flange, overlapping in assembling ranges, as well as reinforcements at openings. With existing methods whole structures with these specialties cannot be treated. All element formulations which use global layer wise nodal degrees of freedom to obtain the three dimensional stress and strain state are not suitable. This statement also holds for 3D-full scale computations, since due to the computational effort only detailed problems can be handled. Therefore an essential demand for the global part of the two-scale model is the use of the standard 5 or 6 nodal shell degrees of freedom. Basing on the previous research, geometrical nonlinearity is to be added to the local part of the two-scale model. The local model can be considered as a one-dimensional representative volume element (RVE). This comes with a significant reduction of computing time, compared with conventional three-dimensional RVEs. With the extension an interface to arbitrary nonlinear three-dimensional material laws is available.Delamination is the most important failure mode of laminated fiber reinforced polymers. Since local displacement degrees of freedom are used at the layer boundaries, it is possible to expand the current model to describe delamination. With the introduction of double nodes or so called processing layers discontinuous displacements can be described. Stresses and tangential matrices are obtained through irreversible cohesive laws. The developed two-scale shell model will be applied to above mentioned practical problems. For simple geometries comparisons with the results of existing costly 3D-models and related assessments will be performed.

• DFG Programme: Research Grants