Papers by C.m. Mota Soares
… Conference on Composite …, 2005
Advances in the Analysis and Design of Composites, 1996
ABSTRACT This work provides an assessment of layerwise mixed models using least-squares formulati... more ABSTRACT This work provides an assessment of layerwise mixed models using least-squares formulation for the coupled electromechanical static analysis of multilayered plates. In agreement with three-dimensional (3D) exact solutions, due to compatibility and equilibrium conditions at the layers interfaces, certain mechanical and electrical variables must fulfill interlaminar C0 continuity, namely: displacements, in-plane strains, transverse stresses, electric potential, in-plane electric field components and transverse electric displacement (if no potential is imposed between layers). Hence, two layerwise mixed least-squares models are here investigated, with two different sets of chosen independent variables: Model A, developed earlier, fulfills a priori the interlaminar C0 continuity of all those aforementioned variables, taken as independent variables; Model B, here newly developed, rather reduces the number of independent variables, but also fulfills a priori the interlaminar C0 continuity of displacements, transverse stresses, electric potential and transverse electric displacement, taken as independent variables. The predictive capabilities of both models are assessed by comparison with 3D exact solutions, considering multilayered piezoelectric composite plates of different aspect ratios, under an applied transverse load or surface potential. It is shown that both models are able to predict an accurate quasi-3D description of the static electromechanical analysis of multilayered plates for all aspect ratios.
WIT Transactions on the Built Environment, 1995
In this paper a finite element model for the static analysis of multi-laminated composite or sand... more In this paper a finite element model for the static analysis of multi-laminated composite or sandwich beams is presented. The model is based on the nonlinear transverse shear deformation theory with nonlinear transverse displacement. This theory enables the nonlinear variation of displacements through the composite beam thickness, thus eliminating the use of shear correction factors. This nonlinear shear deformation model is based on a four node cubic element, enabling the realistic prediction of interlaminar stresses. The transverse shear stress and normal stress perpendicular to geometric axis of the beam, are evaluated directly through the integration of the equilibrium equations. The efficiency and accuracy of the model are discussed with reference to the applications.
This paper deals with a finite element formulation based on the classical laminated plate theory,... more This paper deals with a finite element formulation based on the classical laminated plate theory, for active control of thin plate laminated structures with integrated piezoelectric layers, acting as sensors and actuators. The control is initialized through a previous optimization of the core of the laminated structure, in order to minimize the vibration amplitude. Also the optimization of the patches position is performed to maximize the piezoelectric actuator efficiency. The simulating annealing method is used for these purposes. The finite element model is a single layer triangular nonconforming plate/shell element with 18 degrees of freedom for the generalized displacements, and one electrical potential degree of freedom for each piezoelectric element layer, which can be surface bonded or imbedded on the laminate. To achieve a mechanism of active control of the structure dynamic response, a feedback control algorithm is used, coupling the sensor and active piezoelectric layers. To calculate the dynamic response of the laminated structures the Newmark method is considered. The model is applied in the solution of an illustrative case and the results are presented and discussed.
Composite Structures, 2019
Three-dimensional (3D) exact hygrothermal elasticity solutions are developed to study the behavio... more Three-dimensional (3D) exact hygrothermal elasticity solutions are developed to study the behaviour of simply supported rectangular multilayered composite plates, considering any combination of orthotropic and/or isotropic layers, under hygro-thermo-mechanical loadings. In agreement with the 3D exact elasticity solutions derived by Pagano in the early 1970s, the form of the through-thickness exact solutions of any given layer depends, in fact, on whether the layer material is isotropic or (at most) orthotropic. The 3D exact thermoelastic solutions found, already available, consider either only isotropic layers or only (at most) orthotropic composite layers. This work aims to be all-inclusive, in addition to a further development by considering hygrothermal elasticity. The results here presented consider composite laminates, fibre metal laminates and sandwich plates with different side-to-thickness ratios under a series of hygro-thermo-mechanical loadings. A transverse mechanical load and/or thermal load and/or hygroscopic load are imposed on the multilayered plate top and bottom surfaces to study the effects of hygrothermal environments in the multilayered plate behaviour. These effects are demonstrated by the through-thickness distributions of displacements, stresses, temperature and weight percent moisture content for the selected multilayered plates under different hygro-thermo-mechanical loadings, which may serve as 3D benchmark exact solutions.
Composites Part B: Engineering, 2019
This work presents a new layerwise mixed model for the static analysis of multilayered plates wit... more This work presents a new layerwise mixed model for the static analysis of multilayered plates with embedded functionally graded material (FGM) layers subjected to transverse mechanical loads. This model is capable to fully describe a two-constituent metal-ceramic FGM layer continuous variation of material properties in the thickness direction, using any given homogenized method to estimate its effective properties. The present model is based on a mixed leastsquares formulation with a layerwise variable description for displacements, transverse stresses and in-plane strains, chosen as independent variables. This mixed formulation ensures that the interlaminar C 0 continuity requirements at the layers interfaces, where the material properties actually change, are fully fulfilled a priori for all independent variables. The order of the in-plane twodimensional finite element approximations and the order of the z-expansion through each layer thickness, as well as the number of layers, whether FGM layers or not, are considered free parameters. The full description of the FGM effective properties is achieved by applying to the z-continuous elastic coefficients a z-expansion through the layer thickness of a given order, set as an added free parameter, in a similar approach to finite element approximations. The numerical results consider both single-layer and multilayered functionally graded plates with different side-to-thickness ratios, using either Mori-Tanaka or the rule of mixtures estimates for the FGM effective properties with different material gradation profiles. The present model results are assessed by
Cold 10% trichloroacetic acid was used to extract antigens from purified cell walls of Streptococ... more Cold 10% trichloroacetic acid was used to extract antigens from purified cell walls of Streptococcus mutans BHT. Column chromatography on Biogel P-100 resolved two serologically reactive fractions (B and C). These fractions were ascertained to be relatively pure by recycling on Biogel P-100, Ouchterlony double-diffusion analysis, and immunoelectrophoresis. Fractions B and C demonstrated bands of absolute homology by double-diffusion but different mobilities by immunoelectrophoresis. Chemical analysis indicated that fraction B is a polysaccharide composed principally of rhamnose and galactose, with smaller amounts of glucose and glucosamine. Small quantities of glycerol and phosphorus also were found. Fraction C was composed mainly of galactose, glycerol, and phosphorus. Alkaline hydrolysis of this fraction yielded products typically released by the degradation of a glycerol teichoic acid, such as glycerol monophosphate, glycerol diphosphate, inorganic phosphorus, and several glycosyl glycerol phosphates. Diglycerol triphosphate was not detected. Side-group analysis revealed that glycerol was substituted by mono-and trigalactosyl moieties. Fraction C was deduced to contain 25 glycerol phosphate units per polymer length. Hapten inhibition studies revealed a f,-galactoside as the probable hapten on this antigen. The BHT teichoic acid reacted strongly with FA-1 antiserum. It showed bands of homology with both BHT and FA-1 crude acid extracts upon double-diffusion, using antisera to either strain. The BHT teichoic acid also displayed immunoelectrophoretic behavior identical to one of the mobile FA-1 cell wall antigens, again using either serum to develop precipitin bands. It is concluded this antigen may possess a serotype-specific determinant for S. mutans serotype b. ' Paper no. 5040 in the Journal Series of the Florida Agricultural Experiment Station.
Applied Composite Materials, 2016
This work is dedicated in honour of Professor J.N. Reddy on his 70 th birthday and for his contri... more This work is dedicated in honour of Professor J.N. Reddy on his 70 th birthday and for his contribution and impact to research and education on mechanics of advanced composite materials and structures. The authors also express their gratitude for his friendship and scientific advices.
Computational Fluid and Solid Mechanics, 2001
Computers & Structures, 2011
This paper presents a structural damage location method that decreases the number of spatial diff... more This paper presents a structural damage location method that decreases the number of spatial differentiations needed to compute modal curvature fields. The method is numerically and experimentally applied to isotropic and laminated rectangular plates, respectively. A speckle shear interferometer is used to measure the rotation fields of the laminated plate, while the isotropic plate is analysed by finite elements. It was found that the Gaussian differentiation is the most suited technique to compute the curvature fields. It is also demonstrated the superior performance of the curvature method using measured rotation fields instead of measured displacement fields.
Composite Structures, 2005
A damage identification technique based on frequency response functions (FRF) sensitivities is pr... more A damage identification technique based on frequency response functions (FRF) sensitivities is presented. This technique leads to a set of linear equations, which is solved using an algorithm that constrains the solution to be physically admissible. Damage simulation and identification on a laminated rectangular plate is performed. The influence of the number of natural frequencies and mode shapes used on the FRF computation, as well as the frequency range, the excitation location and the number of measured degrees of freedom (m-DOF) is studied. Numerical tests show that the best accuracy is obtained when using the dynamic expansion of the m-DOF. It is also demonstrated that for small damage the errors are the main influence, whereas for large damage the model incompleteness becomes the most important factor in the results. A procedure for weighting and deletion of equations is used to obtain better identification results. The results of the technique presented in this paper versus those obtained by a technique based on modal data is also discussed.
Composite Structures, 2000
This paper deals with a numerical technique for the identification of damage on laminated structu... more This paper deals with a numerical technique for the identification of damage on laminated structures. The numerical model is based on a first-order shear deformation finite element. When the structure undergoes some kind of damage, its stiffness is reduced, changing the dynamic response. By considering the sensitivities of the orthogonality conditions of the mode shapes, an algorithm is formulated, which
Composite Structures, 2006
Three methods for the damage localization of impact damage in laminated composite plates, based o... more Three methods for the damage localization of impact damage in laminated composite plates, based on their vibrational characteristics, are presented in this paper. These methods use double pulse TV holography with acoustic excitation for mode shapes acquisition and the differences in translations, rotations and curvatures. The rotations and curvatures are obtained by numerical differentiation of mode shapes translations using a differentiation/smoothing technique. The methods are applied to a carbon fiber reinforced epoxy rectangular plate, free in space, subjected to two cases of impact damage. It is shown that the method based on curvatures allows the localization of both cases of damage, which can be undetected by visual, X-ray or C-scan inspections. The best localizations are achieved by selecting and applying the method to the most changed mode.
Composite Structures, 2003
This paper presents a study of the influence of model incompleteness and errors in a structural d... more This paper presents a study of the influence of model incompleteness and errors in a structural damage identification technique based on modal data, leading to a set of linear equations. To deal with the incompleteness three methods are used: (1) dynamic and (2) static expansions of measured degrees of freedom and (3) replacement of unmeasured degrees of freedom by their undamaged counterparts. These methods are applied on damage identification of a laminated rectangular plate. The numerical tests show that the best accuracy is obtained with the dynamic expansion, followed by the static expansion and finally, the replacement of unmeasured degrees of freedom. It is also demonstrated that for small damage the errors are the main influence, whereas for large damage the incompleteness becomes the most important factor in the results. The identification of small and large damages is performed by deleting non-reliable equations, i.e., equations that contain large errors.
This paper deals with a finite element formulation based on the classical laminated plate theory,... more This paper deals with a finite element formulation based on the classical laminated plate theory, for active control of thin plate laminated structures with integrated piezoelectric layers, acting as sensors and actuators. The control is initialized through a previous optimization of the core of the laminated structure, in order to minimize the vibration amplitude. Also the optimization of the patches position is performed to maximize the piezoelectric actuator efficiency. The simulating annealing method is used for these purposes. The finite element model is a single layer triangular nonconforming plate/shell element with 18 degrees of freedom for the generalized displacements, and one electrical potential degree of freedom for each piezoelectric element layer, which can be surface bonded or imbedded on the laminate. To achieve a mechanism of active control of the structure dynamic response, a feedback control algorithm is used, coupling the sensor and active piezoelectric layers. To calculate the dynamic response of the laminated structures the Newmark method is considered. The model is applied in the solution of an illustrative case and the results are presented and discussed.
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Papers by C.m. Mota Soares