The behavior of discrete or continuum structures under impact forces makes their risk and damage mechanisms more and more complex and may causes crack propagations between their different elements or plies even at low impact velocities. In this context, the internal structural failure and crack propagation analysis of composite materials under the effect of external solicitations has been studied. As a result, several microscopic and macroscopic defects may appear within the composite structure that may produce their destruction or the disaster of the hall material. To prevent this phenomenon, adaptable or "smart" materials are incorporated between the fibers of the material in order to control their health state and to determine the weakness of their structure or the beginning of their failure. Consequently they will adapt adequate answers by announcing specific modification or by causing specific actions of correction which will appear in the environment and will protect the material or the structure from the hall disaster. The application fields of these types of smart and adaptable materials are of a great importance in the areas of new technologies such as in tall buildings and bridges to prevent their disaster from the earthquakes and external excitations. They are also operationally used in space structures, in aeronautic constructions and in biomechanics or medical professions to control their behavior and to allow them to get to their initial positions after large deformations or high internal stresses before their total destruction. These materials or structures are made of new materials and/or systems which allow them to fell and control their own characteristics and their own state to attain a higher level of operational performance than those of conventional materials or structures.In our work, smart materials with shape memory alloy and piezoelectric materials, their definitions, their principle works and their super thermo elasticity phenomenon will be considered. The crack propagation analysis of a laminate composite material of carbon/epoxy types under the effect of the external forces was studied. It was found that during the appearance of cracking in the matrix, a discontinuity of the curve stress/strain is observed. It was also noted that the appearance of the cracks increases in a more particular way when the loads are applied perpendicularly to fibers. The control of this crack propagation was reached using adaptable sensors of PZT types and the finite element models to get the displacement at every nodal point. It was noted that the presence of delamination fibers is observed when the PZT static capacity induces a brutal increase in electrical tension which explain the apparition of the crack propagation. Keyword-Laminated Composites, smart materials, external solicitations, crack propagation, disaster protections and finite elements.I.
Purpose Safety improvement and cost reduction have a strong influence on the way to achieve maintenance operations of complex structures, in particular in air transportation, in civil engineering and others. In this case, piezoelectric ceramics such as sensors and actuators have been used. The advantages of piezoelectric materials include high achievable bandwidth, reliability, compactness, lightness and ease of implementation, thus making them well-suited to be used as actuators and sensors in the case of onboard structures. In this context, this study based around the examination of health and deformation of smart structures, taking into consideration the mechanical and piezoelectric behaviour of sensors and actuators, mechanical contact as well as the initial conditions and the imposed boundary conditions. This paper aims to present an approach for modeling of an intelligent structure by the finite element method. This structure is of aluminum type beam with elastic behaviur where piezoelectric rectangular pellets discreetly spread on the surface of the beam are instrumented. The numerical results were computed and compared to the experimental tests available in the literature and the results show the effectiveness of these piezoelectric (PZT) elements, depending on their positions, and to control the deformed structure, good agreement has been found between the experimental data and numerical predictions. Design/methodology/approach Numerical modeling by finite elements model for the measurement of the deformation and the change in shape of a clamped-free structure composed of both elastic and piezoelectric materials have been given by using the Ansys® software. The numerical results were valid by comparisons with analytical and experimental results find in the literature. Findings The numerical results showing a good correlation and agree very well. It was also concluded that the actuator and the sensor will be better placed at the housing because it is the position or the actuator that has the greatest impact and where the sensor gives the greatest signal. They are said to be co-located as glues one below the other on either side of the beam. Originality/value These materials have an inverse piezoelectric effect allowing them to control the form and present any noise or vibration at any time or position on the structure. The study presented in this paper targets the modeling of a PZT beam device for deform generation by transforming electrical energy into usable load. In this paper, a unimorph piezoelectric cantilever with traditional geometry is investigated for micromanipulation by using the software Ansys®.
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