Tesis doctoral de Luis Tavara Mendoza
The present thesis has been developed in the grupo de elasticidad y resistencia de materiales, departamento de mecánica de medios continuos, teoría de estructuras e ingeniería del terreno de la universidad de sevilla (group of elasticity and strength of materials, department of continuum mechanics at the university of seville). the work is included in two fundamental research lines of the grupo de elasticidad y resistencia de materiales: (i) the development and implementation of different fracture mechanics models in some boundary element method (bem) codes, used as a numerical tool to model the elastic problem. In particular, in this thesis a linear elastic-brittle (weak) interface model and a cohesive zone model are implemented. (ii) the study of some mechanical properties of composite materials and different damage and/or failure mechanisms on macro, meso and micro scale that can be developed in these materials and their adhesively bonded joints. the long-term and general objective of this thesis is to contribute to the development of physically based failure criteria for composite materials and their joints. In the last years, many finite element method (fem) codes try to include some cohesive zone models (czm) to solve fracture problems. The czm is characterized by a non-singular stress field in the crack tip neighborhood allowing for an efficient modeling of crack onset and growth using (quasi) uniform meshes. Thus, the initial motivation of the present study was to develop a numerical tool based on the bem that included some non-singular fracture mechanics models, including czm and possibly other models. Due to the fact that all the non-linearities that arise in the use of cohesive zone models are located in the boundary, the bem seemed to be a nice tool to solve the corresponding non-singular fracture problems. the tasks carried out to contribute to fulfill these general objectives are described in the following. development of theoretical formulation and codes implementation: * cohesive zone model, to study the crack onset and growth inside homogeneous materials and at interfaces, including: -suitable implementation of a cohesive zone model into a 2d symmetric galerkin bem code for the analysis of plane problems. -the development and use of arc-length algorithms, to solve nonlinear problems in presence of cohesive zone models, with several variants. * linear elastic-brittle interface model, to study the crack onset and growth at interfaces, requiring: -suitable implementation of linear elastic-brittle model into the collocational bem code for the analysis of plane and axisymmetric problems, that allows the use of non-conforming meshes and contact zones. -the development and use of a sequentially linear solving algorithm. -a computing time improvement by the use of an efficient linear solver in the collocational bem code. * application of bem to the solution of 3d problems of composite materials, involving: -the development of general and efficient expressions of the fundamental solutions and its derivatives for transversely isotropic materials. -implementation of the fundamental solutions and its derivatives in a collocational 3d bem code. study of relevant particular cases of damage mechanisms, in form of cracks onset and growth, in composite materials at macro, meso and micro scale by means of the linear elastic-brittle interface model introduced. * analysis of a crack in a thin adhesive layer in a dcb specimen (macro scale). * delamination cracks in [0/90] symmetric laminates (meso scale). * the single fibre fragmentation test (micro scale). * micro-mechanical behavior of cracks between matrix and fibre under transversal loads (micro scale).
Datos académicos de la tesis doctoral «Damage initiation and propagation in composite materials. boundary element analysis using weak interface and cohesive zone models«
- Título de la tesis: Damage initiation and propagation in composite materials. boundary element analysis using weak interface and cohesive zone models
- Autor: Luis Tavara Mendoza
- Universidad: Sevilla
- Fecha de lectura de la tesis: 19/07/2010
Dirección y tribunal
- Director de la tesis
- Vladislav Mantic
- Tribunal
- Presidente del tribunal: federico París carballo
- dominique Leguillon (vocal)
- roman Vodicka (vocal)
- pietro Cornetti (vocal)