Publication :


Title:

Semi-continous approach for the modelling of complex shaped thick composite parts

Authors: S. Arki, S. Marguet, J.-M. Redonnet, J.-F. Ferrero, P. Navarro and A. Aury
Year: juillet 2016
Proceedings de : 2nd International conference on mechanics of composites.
ISBN : 978-88-7488-963-1
Pages 176

DOI: 10.15651/978-88-748-8963-1

Abstract:
In the aeronautical industry, metallic materials are more and more often replaced by composite materials for structural parts. This trend can be explained by the high level of specific performance of composite materials in terms of stiffness, of strength and of resistance to fatigue. This change of constitutive materials induces an evolution of the methods used to design and size the structures. While the ruin of metals is mainly driven by plasticity and damage mechanisms, the ruin of composite parts relies on a large number of complex phenomena such as the brittle fracture of fibres in tension, the micro-buckling in compression, the decohesion between fibres and matrix, the intra-laminar cracking and the delamination. One way to prevent the occurrence of this last phenomenon, highly critical for the structure safety, consists to ensure that the resin is loaded in out-of-plan compression so as to significantly increase its mechanical strength in case of shear solicitation. To reach this goal, engineers more and more often design parts with complex shapes with the idea to lock the apparition of out-of-plan tensile loading in the laminate. As an example, it is now quite common to add ribs to composite brackets in order to block the delamination due to the unfolding of the curved area. In the presented work, a new method dedicated to the modelling of laminated composite parts of complex shapes is proposed. It relies on a semi-continuous approach [1] in which an explicit distinction is done between the fibres and the resin. The fibres are modelled with one dimensional trusses finite elements whereas the resin is meshed with three dimensional elements. This separation appears to be essential for the capability of the model to predict, with a satisfactory accuracy, the initiation areas of delamination. In a first step, the neutral surface of the whole part is modelled with an analytical equation in the form of a Bezier's patch. Once defined the laminating sequence, this original surface is duplicated at the level of the neutral surface of each ply of the laminate. The weaving of the associated patches is then performed thanks to an algorithm which lays the fibres in such a way they follow the local curvature of the surface. A three-dimensional Delaunay's triangulation then builds the tetrahedra that link the fibres together. At last, the mechanical behaviour laws (elastic with brittle tensile failure for the fibres and elastic with Drucker-Prager plasticity and failure for the resin) are introduced into the model as well as the contact between the fibres. The first results obtained with the model are presented and compared with experimental results coming from a tests campaign. For this purpose, the unfolding of an L shaped laminated composite part under bending loading is studied. The capability of the model to predict the delaminated areas is discussed and some ways of improvement are proposed.

Bibtex citation :
@INPROCEEDINGS{Arki2016,
Author={Arki, S. and Marguet, S. and Redonnet, J.-M. and Ferrero, J.-F. and Navarro, P. and Aury, A.},
Title={Semi-continous approach for the modelling of complex shaped thick composite parts},
Booktitle={2nd International conference on mechanics of composites},
Pages={176},
Year={2016}}


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