Effect In Laminated Composites Research Articles

Modeling the R-curve effects in laminate composites using the interface thick level set method

This paper presents a new model for simulating delamination growth in composites in presence of the resistance curve (R-curve) effects. This model is extended from the interface thick level set (ITLS) method which is developed recently. In this approach the common definition of damage in the constitutive relationship of the interface elements is replaced with a new damage definition based on the thick level set (TLS) method. This new damage definition provides a direct link between fracture and damage mechanics that allows use of interface elements without a predefined cohesive law. In this paper the ITLS method is adopted to incorporate the R-curve effects caused by extended bridging, in modeling delamination. The fracture energy in the developed model is defined as a function of the crack length which allows simple use of experimentally measured R-curve as a direct input of this model. This is in contrast with the popular cohesive models that need to develop some mathematical relationships to extract the cohesive law parameters from experimental R-curve. The proposed 3D model is validated against experimental data obtained from literature to support the accuracy of obtained results.

Engineering Resonance Modes for Enhanced Magnetoelectric Coupling in Bilayer Laminate Composites for Energy Harvesting Applications

The magnetoelectric (ME) effect in composites, a strain-mediated coupling phenomenon between piezoelectric and magnetostrictive phases, has a wide range of technological applications. Here, ME coupling phenomena are explored in $\mathrm{Pb}$-free piezoelectric, $0.5\mathrm{Ba}({\mathrm{Zr}}_{0.2}{\mathrm{Ti}}_{0.8}){\mathrm{O}}_{3}\text{\ensuremath{-}}0.5({\mathrm{Ba}}_{0.7}{\mathrm{Ca}}_{0.3}){\mathrm{Ti}\mathrm{O}}_{3}$ and piezomagnetic ${\mathrm{Ni}\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ bilayer laminate composites. The direct and converse ME coupling strengths are found to be enhanced at the electromechanical resonance modes, rather than at the off-resonance frequencies. Here, it is proposed to further enhance the ME coupling strength at electromechanical resonance modes by the in-phase superimposition of the radial and second bending modes via varying the bilayer thickness, which, in turn, varies the volume fraction of the bilayer. The proposed enhanced ME coupling is experimentally demonstrated at a theoretically envisaged bilayer thickness of about 1.8 mm. This results in a large direct ME coupling coefficient of $22.5\phantom{\rule{0.1em}{0ex}}\mathrm{V}\phantom{\rule{0.1em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.1em}{0ex}}\mathrm{O}{\mathrm{e}}^{\ensuremath{-}1}$, which is around 100% more than the values observed at individual resonance modes. The results are further validated by calculations from theoretical models. The method adopted in this work gives a roadmap to the significant enhancement of the ME effect in laminate composites.

Symmetric relationships between direct and converse magnetoelectric effects in laminate composites

Direct magnetoelectric (DME) and converse magnetoelectric (CME) effects are two opposite processes in magnetoelectric (ME) materials. An ME theoretical model about the longitudinal vibration was proposed to research their relationships in a laminate composite based on equivalent circuit. Following the piezoelectric and magnetostrictive constitutive equations, we deduced magnetic-mechanical-electric equations, and then built a symmetric equivalent circuit about the ME coupling, based on which we analyzed the CME and DMD effects equivalently. A simple laminate composite was prepared by bonding Terfenol-D and Pb(Zr,Ti)O3 plates together for a experimental research. Theoretical calculations meet the experimental results very well. The CME and DME effects exhibit enhanced energy transitions at the resonance frequency with a large phase shift of about π. The ME composite shows CME and DME frequency multiplying behaviors and inhomogeneous CME and DMD responses. The CME and DME as well as their resonance frequencies present nonlinear characteristics with the bias magnetic field. The CME resonance frequency is lower than the DME resonance frequency in a same sample. CME decreases while DME increases with the magnetostrictive layer. The theoretical model plays an important role in the comprehensive understanding of ME properties, especially the CME effect, and design of ME devices such as magnetic-electric field sensors, energy harvesting transducers and solid tunable transformers.

Photopiezoelectric Composites of Azobenzene‐Functionalized Polyimides and Polyvinylidene Fluoride

Light is a readily available and sustainable energy source. Transduction of light into mechanical work or electricity in functional materials, composites, or systems has other potential advantages derived from the ability to remotely, spatially, and temporally control triggering by light. Toward this end, this work examines photoinduced piezoelectric (photopiezoelectric) effects in laminate composites prepared from photoresponsive polymeric materials and the piezoelectric polymer polyvinylidene fluoride (PVDF). In the geometry studied here, photopiezoelectric conversion is shown to strongly depend on the photomechanical properties inherent to the azobenzene-functionalized polyimides. Based on prior examinations of photomechanical effects in azobenzene-functionalized polyimides, this investigation focuses on amorphous materials and systematically varies the concentration of azobenzene in the copolymers. The baseline photomechanical response of the set of polyimides is characterized in cantilever deflection experiments. To improve the photomechanical response of the materials and enhance the electrical conversion, the polyimides are drawn to increase the magnitude of the deflection as well as photogenerated stress. In laminate composites, the photomechanical response of the materials in sequenced light exposure is shown to transduce light energy into electrical energy. The frequency of the photopiezoelectric response of the composite can match the frequency of the sequenced light exposing the films.

Three-Dimensional Investigation of Free-Edge Effects in Laminate Composites Using X-ray Tomography and Digital Volume Correlation

Laminate composite materials are widely used for many industrial applications because of their high specific mechanical properties as well as the possibility to adapt the structure properties to its application and loading conditions by optimization of the stacking sequence. It is now well known that the mechanical properties mismatch of adjacent layers having different fibre orientation induces stresses concentrations at interlaminar interfaces in the vicinity of structure edges. Edge effects experimental investigation is generally made through two dimensional measurements, crack initiation detection and characterization using various observation techniques. In this paper, it is proposed to investigate edge effects by coupling 2D and 3D measurements, using X-Ray tomography and kinematic field measurements. A preconditioned Digital Volume Correlation is developped in order to capture the in depth evolution of the residual displacement discontinuity at the ply interfaces. After it has been validated by comparison with the 2D measurements on the surface, the analysis of the 3D fields is carried out.

Wide-bandwidth high-sensitivity magnetoelectric effect of magnetostrictive/piezoelectric composites under adjustable bias voltage

This paper presents a wide-bandwidth high-sensitivity magnetostrictive/piezoelectric magnetoelectric (ME) composite (PZT-5/Terfenol-D/PZT-8). The resonant frequencies of the ME laminate structure can be adjusted by modulating the bias voltage across PZT-5 layer. Model and methods for the resonant ME effects in laminate composites under adjustable bias voltages are presented. The relationships between the control voltage, the strain, the Young's modulus, the first-order resonant frequencies and the resonant ME coefficient are analyzed. Theoretical analyses show that the first-order resonant frequencies of the laminate structure are almost a linear function of the applied dc bias voltage at a small strain. The ME coefficient is hardly related to the control voltage. The experimental results are in good agreement with the analytical results. For a control voltage of ±170V, the first-order resonant frequencies can be linearly adjusted. The adjusted maximum of the resonant frequency is 1kHz. The ratio of the adjusted value to the bias control voltage is 2.94Hz/V. For the larger control voltage (such as ±350V), the wider adjusted resonant frequency (over 2kHz or 1.73%) can be obtained. Thus, the ME composite with a high sensitivity and a wide frequency bandwidth can be used in ME transducer and energy harvesting.

Direct and converse effect in magnetoelectric laminate composites

In this letter, we analyze the direct and converse effect in laminate composites of magnetostrictive and piezoelectric materials. Our results deterministically show that direct magnetoelectric (ME) effect is maximized at antiresonance frequency while the converse ME effect is maximized at resonance frequency of the laminate composite. We explain this phenomenon by using piezoelectric constitutive equations and combining it with resonance boundary conditions. The dominant factor controlling the position of peak ME coefficient was found to be frequency dependent capacitance of piezoelectric layer. This study will provide guidance toward the development of magnetic field sensors based on direct effect and communication components based on converse effect.

Theory of magnetoelectric effect in laminate composites considering two-dimensional internal stresses and equivalent circuit

By taking into account the transverse stresses produced in both the transversely poled piezoelectric plate and the longitudinally magnetized magnetostrictive plate, we develop an 2D stresses magnetoelectric (ME) effect theoretical model. The ME voltage expressions are given by combing constitutive equations and equation of motion for the ME element, accompanied by boundary conditions and charge source equivalent circuit. Theoretical results show the detailed relationships among ME voltage coefficient, geometric parameters, and physical parameters of the composites, as well as the circuit parameters. Compared with 1D stresses theory, the 2D stresses theoretical results are in better agreement with the experimental data.

Theoretical model for the magnetoelectric effect in magnetostrictive/piezoelectric composites

A theoretical model for the longitudinal magnetoelectric effect in laminate composites comprising magnetostrictive and piezoelectric phases is presented. The model characterizes the magnetoelectric media in terms of its permeability, permittivity, and magnetoelectric-susceptibility tensor. A distinct approach to model the media is presented, in which fundamental electromagnetic boundary conditions are applied to all fields existing at the interface between the layers, and in the composite material in general. The application of the boundary condition used here represents a change from previous models where quasistatic approximations are used, including open circuit conditions imposed on the electric displacement field. The model presented here takes into account the imperfect coupling in terms of the existing mechanical forces (stress, strain) that can occur at the interface of such layered composites. An interface coupling parameter is used to model the strain relationship between layers of the composite. Results of the theoretical model are compared to experimental data and show much better results than previously obtained.

Enhanced magnetoelectric effects in laminate composites ofTerfenol-D/Pb(Zr, TiO)3 with high-permeability FeCuNbSiB ribbon

The enhancement of resonant magnetoelectric (ME) effectsis reported in the structure consisting of a piezoelectric PZT(Pb(Zr1 − xTix)O3) plate, a magnetostrictiveTerfenol-D (Tb1 − xDyxFe2 − y) plate, and multiple high-permeability FeCuNbSiB(Fe73.5Cu1Nb3Si13.5B9) ribbon plates. The FeCuNbSiB ribbon acts as the dynamic driver to increase the effectivepiezomagnetic coefficient of the Terfenol-D and enhances the effective mechanical quality factor (Qm) of the laminateowing to its high Qm, consequently resulting in the increase of the dynamic strain coefficient of Terfenol-D andthe resonant ME voltage coefficient (MEVC). The experimental results show that theTerfenol-D/PZT/FeCuNbSiB (MPF) composite with double-layer FeCuNbSiB ribbons canachieve a higher resonant MEVC than that with single-layer or other multilayer ribbons,which is 2–3 times as high as that of the Terfenol-D/PZT(MP) composite under a lowHdc. In addition, the ME voltage strongly depends onHdc, the maximumvalue of dVME/dHdc achieves 125.9 mV Oe − 1. The MPF laminate has potential for highly sensitive dc magnetic field sensing.

Comparison of Effective Direct and Converse Magnetoelectric Effects in Laminate Composites

A theoretical analysis is used to prove that a piezoelectric/magnetostrictive laminate composite has equivalent effective direct and converse magnetoelectric (ME) coefficients. Experimentally a PZT/Terfenol-D/PZT trilayer laminate composite was fabricated and both direct and converse ME coefficients were characterized by measuring the magnetic-field-induced polarization and electric-field-induced magnetization. The laminate sample exhibits similar DC magnetic bias dependence and resonance response for both direct and converse ME effects. The magnitudes of effective ME coefficients are of the same order but significantly different and both are smaller than theoretical prediction. This raises the question as to whether these coefficients are equivalent in a layered composite or to the accuracy of ME coefficient data measurement.

Magnetoelectric effect in laminate composites of Tb1−xDyxFe2−y and Cr doped BaTiO3

Cr doped BaTiO3 has been synthesised with sol–gel technique. Its transformation point of ferroelectric to paraelectric and the latent heat of the transformation were observed respectively. They are a little less than those for pure BaTiO3. Bonded layered composites Tb1−xDyxFe2−y–BaTi0·99Cr0·01O3 have been fabricated. Their magnetoelectric (ME) effects have been investigated. The transverse ME voltage coefficients for the bilayer Tb1−xDyxFe2−y–BaTi0·99Cr0·01O3 and the trilayer Tb1−xDyxFe2−y–BaTi0·99Cr0·01O3–Tb1−xDyxFe2−y can reach 732·5 and 2753 mV Oe−1 cm−1 respectively, under a bias magnetic field 355 Oe at room temperature. These are about 54 and 56% larger than those for the bilayer and trilayer composed by pure BaTiO3 respectively. This suggests that the doped BaTiO3 can be a new choice of piezoelectrics to compose ME composites.

Magnetoelectric effect in laminate composites of Tb1−xDyxFe2−y and Fe-doped BaTiO3

Fe-doped BaTiO3 has been synthesized with sol-gel technique. Its transformation point of ferroelectric to paraelectric and the latent heat of the transformation were observed at 103.27 °C and 169.9 J/mol, respectively. They are a little less than those for pure BaTiO3. Bonded layered composites Tb1−xDyxFe2−y/BaTi0.99Fe0.01O3 have been fabricated. Their magnetoelectric (ME) effect has been investigated. The transverse ME voltage coefficient for the bilayer Tb1−xDyxFe2−y–BaTi0.99Fe0.01O3 and the trilayer Tb1−xDyxFe2−y–BaTi0.99Fe0.01O3–Tb1−xDyxFe2−y can reach 578 (mv Oe−1 cm−1) and 2100 (mv Oe−1 cm−1), respectively, under a bias magnetic field of 350 Oe at room temperature. Those are about 50% larger than those for the bilayer and trilayer composed by pure BaTiO3. It suggests that the doped BaTiO3 can be a new choice of piezoelectrics to compose ME composites.

Enhanced magnetoelectric effects in laminate composites of Terfenol-D/Pb(Zr,Ti)O3 under resonant drive

We have found that laminate composites consisting of longitudinally magnetized magnetostrictive Terfenol-D and longitudinally poled piezoelectric Pb(Zr,Ti)O3 layers have dramatically enhanced magnetoelectric effects when driven near resonance. The maximum induced magnetoelectric voltage at resonance was ∼10 Vp/Oe, which is ∼102 times higher than previous reports at subresonant frequencies.

Giant magnetoelectric effect in laminate composites

It has been found that laminate composites of longitudinally magnetized magnetostrictive and transversely poled piezoelectric layers (an L–T laminate composite) have a giant magnetoelectric (ME) effect. Relatively high ME coupling, that is significant exchange between magnetization and polarization, is demonstrated.

Giant magneto-electric effect in laminate composites

It has been discovered that laminate composites of longitudinally magnetized magnetostrictive and transversely poled piezoelectric layers (a L-T laminate composite) have a giant magneto-electric (ME) effect under a low magnetic bias. The ME voltage coefficient is over 110 mV/Oe at a magnetic bias H = 500 Oe. This value is 5-10 times higher than that previously reported for transverse magnetized/transverse polarized (T-T) laminates of the same layer compositions at the same bias. In this paper, we also report the magneto-elasto-electric bieffect equivalent circuit of the L-T laminate composite and the corresponding theoretical formula of the magneto-electric voltage coefficient.