1,721,041 research outputs found
Structural state awareness of composite structures by blending passive and active acoustic-based health monitoring methods
No full textThis study aims to demonstrate the effectiveness of blending passive and active acoustic-based health monitoring methods to impact damage diagnostics of composite structures. The structural state awareness is introduced as a term to characterize the health condition that a structure is and how this condition can be quantified by blending health monitoring techniques. To this aim, a Carbon Fiber Reinforces Polymer (CFRP) composite plate was fabricated and subjected to a simulated low-velocity impact by performing repeated quasi-static indentation tests where a loading-unloading-reloading test profile was adopted. Two Acoustic Emission (AE) broadband sensors and a network of eight piezoelectric (PZT) sensors were attached on the composite plate surface. AE (passive method) was employed during the loading and reloading phases of the indentation tests to in-situ monitor the damage initiation and progression, while scanning of the plate with Lamb waves (active method) was done to localize the damage when the structure was unloaded. The obtained results showed that the proposed blended passive and active acoustic-based method has the potential to provide useful information about the impact-induced damage in composite structures.Structural Integrity & Composite
Experimental Evaluation of the Effective Electromechanical Coupling of a Vibrating Aircraft-Type Hybrid Honeycomb Sandwich Panel With Bonded Piezoelectric d31 Macro-Fibre Composite (MFC) Patch
No full textThis work presents the experimental evaluation challenges of the modal effective Electro-Mechanical Coupling Coefficient (EMCC) of a hybrid sandwich plate, made of regular (hexagonal) Aluminium honeycomb core and woven glass fibre-reinforced polymer composite faces, on which is bonded a piezoelectric transverse response (d31) Macro-Fibre Composite (MFC) large patch. The testing challenges come from the very light weight of the hybrid sandwich panel and the resulting difficulties to consider, without damaging it, different mechanical boundary conditions (BCs) along its lateral edges. This experimental campaign, using an impedance analyser, complements an earlier one that used an LCR meter. The latter provided only the EMCC of the first three electromechanically coupled modes under free-free (F-F) BCs, while the former reached more accurately eight ones for F-F and clamped-free (cantilever) BCs. Beside graphical form, the obtained frequency and effective EMCC results are given in tabular form, so that they can be used as reference for validating/correlating future numerical models
Advances in piezoelectric finite element modeling of adaptive structural elements: A survey
No full textInternational audienc
Morphology- and Ion Size-Induced Actuation of Carbon Nanotube Architectures
No full textFuture adaptive applications require lightweight and stiff materials with high active strain but low energy consumption. A suitable combination of these properties
is offered by carbon nanotube-based actuators. Papers made of carbon nanotubes (CNTs) are charged within an electrolyte, which results in an electrical field forming
a double-layer of ions at their surfaces and a deflection of the papers can be detected. Until now, there is no generally accepted theory for the actuation mechanism. This study focuses on the actuation mechanism of CNT papers, which represent architectures
of randomly oriented CNTs. The samples are tested electrochemically in an in-plane set-up to detect the free strain. The elastic modulus of the CNT papers is
analyzed in a tensile test facility. The influence of various ion sizes of water-based electrolytes is investigated.
During the tests, four parameters that have a significant influence on the mechanical performance of CNT papers were identified: the test conditions, the electrical
charging, the microstructure and the ion size. All of these influencing factors Point to the mechanically weak inter-tube linking at which the actuation seems to take
place. Quadratic voltage-strain correlation suggests a combination of electrostatic and volumetric effects as the possible reason for CNT paper actuation
Preface: Natural composites and hybrid sandwiches for modern aircrafts and spacecrafts
No full textInternational audienc
FREQUENCY- AND FIELD-DEPENDENT NON-LINEARITIES OF THE SHEAR STRAIN PIEZOELECTRIC COUPLING COEFFICIENT (D15) OF A POLED SOFT PIEZOCERAMIC MATERIAL (PZT PIC255)
No full textInternational audienceThis contribution investigates the non-resonant driving frequency- and AC electric field-dependent operational non-linearities of the thickness-shear strain piezoelectric couplingcoefficient (d15) of poled soft piezoceramic (PZT PIC255) rectangular patches. Therefore, first, an experimental database is analyzed for varying driving frequency (10Hz-1kHz) under fixed input voltages in order to find a threshold frequency from which there is no frequencydependence and, for varying input voltages (20V-400V) under a fixed driving frequency, a threshold voltage from which there is no field-dependence is searched. Then, the Levenberg-Marquardt-Fletcher algorithm is adapted and implemented in order to optimize two-parameter additive and multiplicative power laws for modelling the field-dependent non-linearity of soft piezoceramics. It is found that, while the additive power law is slower than the multiplicative one, they perform similarly for wide ranges of driving frequency (200Hz-1kHz) and actuation voltage (100V-400V). Besides, their two parameters are found frequency-dependent
SELECTED RESULTS ON THE DEVELOPMENT AND TESTING OF SMART BLADES TECHNOLOGIES FOR WIND TURBINES
No full textWithin the frame of the Smart Blades and the SmartBlades2 projects, different technologies for developing smart rotor blades for wind turbines have been developed and are still being studied and tested. These cover the three following technologies: bend-twist coupled rotor blades; rotor blades with trailing edge flaps and rotor blades with leading edge slats. In addition, cross-technology topics that need to be considered for successfully implementing all three technologies as well as for evaluating their performance within a wind turbine system are being studied
Modal effective electromechanical coupling coefficient of shear-mode piezoceramic sandwich cantilevers with segmented multicore: Experimental and numerical assessments
No full textInternational audienceSmart sandwich cantilevers with aluminum faces and single and double cores, formed by assembled shear-mode piezoceramic patches with same poling, are experimentally and numerically assessed for the first time. To measure the electromechanical coupling efficiency of such vibrating smart structures, the so-called modal effective electromechanical coupling coefficient is used as a performance indicator. Hence, it is first experimentally analyzed under different electric connections (short circuit, open circuit, series wiring, and parallel wiring) of the patches’ electrodes; then, it is numerically investigated for models with different refinements (equipotential constraints and bonding adhesives) using ABAQUS ® three-dimensional finite element simulations. It is found that the experimental modal effective electromechanical coupling coefficient is low for the smart shear-mode piezoceramic single core sandwich but can be increased using multilayer designs, as confirmed by the smart shear-mode piezoceramic double core sandwich. Numerically, it is found that the electric connection has less influence on the modal effective electromechanical coupling coefficient evaluation than the equipotential constraints and adhesives modeling, in particular for the smart shear double core sandwich. The proposed two benchmarks can be used by the research community of smart structures, systems, and devices for validating new shear-mode response-based theories and numerical models or designing related engineering applications, such as shunted damping, energy harvesting, structural health monitoring, resonators, and filters
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