Papers by Keyword: Laminate Theory

Abstract: This paper is focused on an analysis of a multilayer ceramic-based piezoelectric vibration energy harvester, which could be excited by ambient vibrations or external forces and thus provide a useful source of electricity for modern electronics. The proposed multilayer concept of the energy harvester enables introduction of tensile / compressive residual stresses inside particular layers. These stresses are intended to be used for enhancement of the harvester ́s fracture resistance and simultaneously for the improvement of the energy gain upon its operation. A crack arrest, by means of compressive residual stresses (in the outer “non-piezo” layer), will be utilized to this end. Primarily, the extended classical laminate theory (taking into account the piezoelectric characteristics of selected layers) will be used to define various designs of particular layers with various levels of residual stresses inside them. The weight function method is subsequently employed to select a design, which is most resistant to propagation of preexisting cracks. Selected laminate configurations are verified by means of FE simulations. Such analysis is essential for development of new energy harvesting systems formed of new smart materials and structures, which could be integrated in future development processes.

Abstract: In this research, both un-deformed or Lagrangian state and deformed or Eulerian state are used to derive for stability analysis and large deformation. By choosing the deformed radius of curvature and deformed angle of tangent slope as parameters, the governing equations of laminated curved beam under static loading are transformed into a set of equations in terms of angle of tangent slope. All the quantities of axial force, shear force, radial and tangential displacements of circular thin curved beam are expressed as functions of angle of tangent slope by using laminate theory. The buckling load and large deformation analytical solutions of circular thin curved beam under a pair of forces are presented as well.

Abstract: Based on the analysis of the woven structure, the compressive fracture process and strength of a 2.5D-C/SiC ceramic matrix composite were investigated by the classical laminate theory. The porous composite was regarded as a spatial layered structure, and the two classes of the warps and wefts in the 2.5D-C/SiC composite were treated as the corresponding layers. The strengths of the C/SiC bundle and C/SiC lamina were determined, and the compression strength for the composite was calculated by progressive fracture method of the layers and elastic degradation. The failure mechanisms and the angles of the compressive fracture surfaces coincided with the experimental result well. It was demonstrated that the strength predictive method of the classical laminate theory can be applied to the analysis of 2.5D-C/SiC composite.

Abstract: The laminated composites undergo chemical deformation on cross-linking and thermal deformation while cooling during fabrication process. In thin laminates, due to large displacements and complex shape evolution, these deformations can only be explained by using nonlinear strain-displacement relationship. In the present article, the thermal and chemical deformations occurring in carbon/epoxy laminates are calculated together for the first time by considering a non-linear geometrical approach, to understand the evolution of shape and hence residual stresses induced during fabrication process.

Abstract: In recent years fibre reinforced plastics play a constantly improving role in a growing field of applications. From the chemical industry through sports equipments up to aircraft production - composites can be used in all these industrial areas. Although materials like glass fibre reinforced or carbon fibre reinforced plastics have a lot of applications in structural parts the knowledge about dimensioning and processing techniques is not exploited for the design of composite structures. If the parts and structures are not built for high performance applications such as in aircrafts, often principles and theories based on metal design are used to design the parts. In this article the basics of structural mechanics for composite materials are presented. An overview about how to work with anisotropic material in design as well as in processing is given and the most important CAE tools for composite design are shortly presented.

Abstract: The paper presents the compatibility relation of displacement, strain energy expression, and the formulations of Finite Element Method in the transitional region for the improved damage model of 2-D delamination[1]. The postbuckling behaviors of composite laminated plate with a circular delamination are analyzed. Results show that the model mainly improves computational results of energy release rates in the delamination front. The model should only be used in a narrow region near the crack-tip and the normal Mindlin model in other regions. It leads to little increase in the amount of computation, but significant improvement in the results.