https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Sun, 14 Jun 2026 10:45:07 GMT 2026-06-14T10:45:07Z http://hdl.handle.net/10985/17462 A general method for the determination of the local orthotropic directions of heterogeneous materials: application to bone structures using µCT images CLUZEL, Christophe; ALLENA, Rachele To assess the degree (i.e., isotropy, transverse isotropy, or orthotropy) and the directions of anisotropy of a three-dimensional structure, information about its mesostructure is necessary. Usually, a topological analysis of computed tomography or microcomputed tomography images is performed and requires an interpretation of the constitutive elements of the three-dimensional structure, which may lead to a simplistic description of the geometry. In this paper we propose an alternative technique based on a geometric tensor and we use it to analyze 38 representative elementary volumes extracted from 24 specimens of cortical bone in a human femur whose geometries have been reconstructed via microcomputed tomography images. Mon, 01 Jan 2018 00:00:00 GMT http://hdl.handle.net/10985/17462 2018-01-01T00:00:00Z CLUZEL, Christophe ALLENA, Rachele To assess the degree (i.e., isotropy, transverse isotropy, or orthotropy) and the directions of anisotropy of a three-dimensional structure, information about its mesostructure is necessary. Usually, a topological analysis of computed tomography or microcomputed tomography images is performed and requires an interpretation of the constitutive elements of the three-dimensional structure, which may lead to a simplistic description of the geometry. In this paper we propose an alternative technique based on a geometric tensor and we use it to analyze 38 representative elementary volumes extracted from 24 specimens of cortical bone in a human femur whose geometries have been reconstructed via microcomputed tomography images. http://hdl.handle.net/10985/17465 Heterogeneous directions of orthotropy in three-dimensional structures: finite element description based on diffusion equations ALLENA, Rachele; CLUZEL, Christophe Heterogeneous materials such as bone or woven composites show mesostructures whose constitutive elements are all oriented locally in the same direction and channel the stress flow throughout the mechanical structure. The interfaces between such constitutive elements and the matrix are regions of potential degradations. Then, when building a numerical model, one has to take into account the local systems of orthotropic coordinates in order to properly describe the damage behavior of such materials. This can be a difficult task if the orthotropic directions constantly change across the complex three-dimensional geometry as is the case for bone structures or woven composites. In the present paper, we propose a finite element technique to estimate the continuum field of orthotropic directions based on the main hypothesis that they are mainly triggered by the external surface of the structure itself and the boundary conditions. We employ two diffusion equations, with specific boundary conditions, to build the radial and the initial longitudinal unit vectors. Then, to ensure the orthonormality of the basis, we compute the longitudinal, the circumferential, and the radial vectors via a series of vector products. To validate the numerical results, a comparison with the average directions of the experimentally observed Haversian canals is used. Our method is applied here to a human femur. Mon, 01 Jan 2018 00:00:00 GMT http://hdl.handle.net/10985/17465 2018-01-01T00:00:00Z ALLENA, Rachele CLUZEL, Christophe Heterogeneous materials such as bone or woven composites show mesostructures whose constitutive elements are all oriented locally in the same direction and channel the stress flow throughout the mechanical structure. The interfaces between such constitutive elements and the matrix are regions of potential degradations. Then, when building a numerical model, one has to take into account the local systems of orthotropic coordinates in order to properly describe the damage behavior of such materials. This can be a difficult task if the orthotropic directions constantly change across the complex three-dimensional geometry as is the case for bone structures or woven composites. In the present paper, we propose a finite element technique to estimate the continuum field of orthotropic directions based on the main hypothesis that they are mainly triggered by the external surface of the structure itself and the boundary conditions. We employ two diffusion equations, with specific boundary conditions, to build the radial and the initial longitudinal unit vectors. Then, to ensure the orthonormality of the basis, we compute the longitudinal, the circumferential, and the radial vectors via a series of vector products. To validate the numerical results, a comparison with the average directions of the experimentally observed Haversian canals is used. Our method is applied here to a human femur. http://hdl.handle.net/10985/18598 Modelling of anisotropic cortical bone based on degradation mechanism CLUZEL, Christophe; ALLENA, Rachele When an orthopaedic prosthesis is implanted, it is essential to ensure bone remodelling and to maintain the proper mechanical properties under specific loading conditions. The coupling between the remodelling and the loading is ensured by the mechanical stress inducing the osteo- genesis around the implant (Frost 2003). The objective of the present work is to develop a finite element tool and a multiscale mechanical model of the behaviour of the cortical bone in order to be able to optimize the stiffness of the prosthetic implant and to avoid overloaded or under- loaded regions. Thu, 01 Jan 2015 00:00:00 GMT http://hdl.handle.net/10985/18598 2015-01-01T00:00:00Z CLUZEL, Christophe ALLENA, Rachele When an orthopaedic prosthesis is implanted, it is essential to ensure bone remodelling and to maintain the proper mechanical properties under specific loading conditions. The coupling between the remodelling and the loading is ensured by the mechanical stress inducing the osteo- genesis around the implant (Frost 2003). The objective of the present work is to develop a finite element tool and a multiscale mechanical model of the behaviour of the cortical bone in order to be able to optimize the stiffness of the prosthetic implant and to avoid overloaded or under- loaded regions. http://hdl.handle.net/10985/8625 Identification of anisotropic tensile strength of cortical bone using Brazilian test. ALLENA, Rachele; CLUZEL, Christophe For a proper analysis of cortical bone behaviour, it is essential to take into account both the elastic stiffness and the failure criteria. While ultrasound methods allow complete identification of the elastic orthotropic coefficients, tests used to characterise the various failure mechanisms and to identify the brittle tensile strength in all directions are currently inadequate. In the present work we propose the Brazilian test as a complement to conventional tensile tests. In fact, this experimental technique, rarely employed in the biomechanics field, has the potential to provide an accurate description of the anisotropic strength of cortical bone. Additionally, it allows us to assess the scale influence on failure behaviour which may be attributed to an intrinsic length in correlation with the cortical bone microstructure. In order to correctly set up the Brazilian test, several aspects such as the machining, the geometrical parameters of the specimen and the loading conditions were determined. The finite element method was used to evaluate the maximal tensile stress at the centre of a 2D anisotropic elastic specimen as a simple function of the loading. To validate the protocol, the Brazilian test was carried out on 29 cortical bovine cylindrical specimens with diameters ranging from 10mm to 4mm. Wed, 01 Jan 2014 00:00:00 GMT http://hdl.handle.net/10985/8625 2014-01-01T00:00:00Z ALLENA, Rachele CLUZEL, Christophe For a proper analysis of cortical bone behaviour, it is essential to take into account both the elastic stiffness and the failure criteria. While ultrasound methods allow complete identification of the elastic orthotropic coefficients, tests used to characterise the various failure mechanisms and to identify the brittle tensile strength in all directions are currently inadequate. In the present work we propose the Brazilian test as a complement to conventional tensile tests. In fact, this experimental technique, rarely employed in the biomechanics field, has the potential to provide an accurate description of the anisotropic strength of cortical bone. Additionally, it allows us to assess the scale influence on failure behaviour which may be attributed to an intrinsic length in correlation with the cortical bone microstructure. In order to correctly set up the Brazilian test, several aspects such as the machining, the geometrical parameters of the specimen and the loading conditions were determined. The finite element method was used to evaluate the maximal tensile stress at the centre of a 2D anisotropic elastic specimen as a simple function of the loading. To validate the protocol, the Brazilian test was carried out on 29 cortical bovine cylindrical specimens with diameters ranging from 10mm to 4mm. http://hdl.handle.net/10985/11315 Thermo-oxidation behaviour of organic matrix composite materials at high temperatures CINQUIN, Jacques; MILLE, Marion; CHOCINSKI-ARNAULT, Laurence; GIGLIOTTI, Marco; GRANDIDIER, Jean-Claude; LAFARIE-FRENOT, Marie-Christine; MINERVINO, Matteo; CLUZEL, Christophe; DAGHIA, Federica; LADEVEZE, Pierre; ZHANG, Fangzouh; FAYOLLE, Bruno; COLIN, Xavier; TEREKHINA, Svetlana The present paper is a review of the main activities carried out within the context of the COMPTINN‟ program, a joint research project founded by a FUI program (Fonds Unifiés Interministériels) in which four research teams focused on the thermo-oxidation behaviour of HTS-TACTIX carbon-epoxy composite at „high‟ temperatures (120°C-180°C). The scientific aim of the COMPTINN‟ program was to better identify, with a multi-scale approach, the link between the physico-chemical mechanisms involved in thermo-oxidation phenomena, and to provide theoretical and numerical tools for predicting the mechanical behaviour of aged composite materials including damage onset and development. Fri, 01 Jan 2016 00:00:00 GMT http://hdl.handle.net/10985/11315 2016-01-01T00:00:00Z CINQUIN, Jacques MILLE, Marion CHOCINSKI-ARNAULT, Laurence GIGLIOTTI, Marco GRANDIDIER, Jean-Claude LAFARIE-FRENOT, Marie-Christine MINERVINO, Matteo CLUZEL, Christophe DAGHIA, Federica LADEVEZE, Pierre ZHANG, Fangzouh FAYOLLE, Bruno COLIN, Xavier TEREKHINA, Svetlana The present paper is a review of the main activities carried out within the context of the COMPTINN‟ program, a joint research project founded by a FUI program (Fonds Unifiés Interministériels) in which four research teams focused on the thermo-oxidation behaviour of HTS-TACTIX carbon-epoxy composite at „high‟ temperatures (120°C-180°C). The scientific aim of the COMPTINN‟ program was to better identify, with a multi-scale approach, the link between the physico-chemical mechanisms involved in thermo-oxidation phenomena, and to provide theoretical and numerical tools for predicting the mechanical behaviour of aged composite materials including damage onset and development.