Abstract: The Green’s-function and the force- and energy-balance equations for steady states have
been used to study the electron transport and its pressure effect with the influence of impurities and
acoustic-phonons in Au1-xTixO3 octahedral crystal potential. The results show that there is a
minimum temperature range of electrons as the center-of-mass velocity of electrons increasing, and
external pressure effect plays an important role in the contributions of impurities and phonons.
Abstract: Lead-free piezoelectric ceramics based on bismuth sodium titanate (BNT) -barium hafnate
titanate (BHT) were prepared by a two-step synthesis process. The final BNT-BHT ceramics sintered
at 1180oC for 2 h in air showed a perovskite structure with high density. The morphotropic phase
boundaries (MPB) were found in BNT based piezoelectric ceramics with 8~10 wt% BHT in
composites. In the case of Bi0.5Na0.5TiO3-0.08BaHf0.05Ti0.95O3 ceramics, a maximum piezoelectric
coefficient d33 of 122.6 pC/N was obtained. The remnant polarization (Pr) and coercive field (Ec) were
measured and the relationship between ferroelectricity and the BHT fraction in the compounds was
investigated. The BNT-BHT ceramics were expected to be a new and promising candidate for
lead-free piezoelectric device applications.
Abstract: This paper describes the piezoresistance behavior in CFRP cross-ply laminates with
transverse cracking loaded in tension. The resistance change due to transverse cracking and the gage
factor (the rate of resistance change per mechanical strain) for each transverse crack density were
experimentally measured during loading/unloading cycles. The resistance change-strain curves in the
unloading/ reloading processes show the bilinear behavior where two gage factors are defined as the
slopes of the bilinear curve. The residual resistance change after full unloading increases almost
linearly with the mechanical strain while the gage factors do not always increase with the strain. The
residual resistance change and gage factors are associated with transverse crack density on the basis of
an equivalent resistance circuit.
Abstract: The method of generating the most practicable shape recovery force in smart composite
materials which embedded shape-memory alloy (SMA) fiber under the resin matrix is electric
heating. However, because the calorie for the heating of the resin matrix increases in the low
temperature environment, it is necessary to control the electric heating corresponding to an ambient
temperature to obtaining a steady shape recovery force. Then, the method of self-detecting the
temperature without using a special temperature sensor by measuring the electrical resistance of the
SMA fiber in the composite material was examined.
Abstract: The dynamic response and the sound radiation of truss core panels are investigated in this
paper. The spectral element model for the truss core panel is developed. The element model is
established by employing shape functions derived directly from the solution of distributed parameter
models for each beam element. Forced vibrations of a fluid-loaded beam in a rigid baffle are
considered. The spectral formulation can be easily and efficiently coupled with the Fourier transform
(FT) based analysis of the structure’s sound radiation in a surrounding acoustic medium. Hence the
proposed formulation is an efficient numerical tool for the analysis of the dynamic and acoustic
performance of the considered truss core sandwich panels. The comparison of the sound
characteristics selected as sound transmission reduction index to the psychical parameters of the truss
core beam is carried out.
Abstract: A nonlinear thermal vibration characteristic of the laminate composite thin shell structures
under linear temperature field is investigated by finite element method (FEM). The natural
frequencies of the composite laminated thin shell structures with different boundary conditions and
stacking sequence are calculated and analyzed. Numerical results show that the natural frequencies of
the structure are affected by the temperature, boundary conditions and the stacking sequence; the
proper stacking angle can change the natural frequencies; the effect degree on the natural frequencies
of symmetric composite structures is different from that of the antisymmetric one. These conclusions
can provide some guidance to structure design and heat-resistant design of composite structures.
Abstract: Barium titanate with A-site substituted by various amount of bismuth oxide (Ba1-x
BixTiO3, abbreviated as BBT, x=0.05, 0.1, 0.15) were prepared by solid-state reaction. The
effect of bismuth substitution on crystallographic phase, dielectric and ferroelectric
properties was studied. The X-ray diffraction shows that the samples were crystallized into
pure perovskite structure when x=0.05 and 0.1, while for x=0.15 sample, second phase
appeared in the dominant perovskite phase. The temperature dependence of dielectric
permittivity of the ceramics was investigated and the evolution from normal ferroelectrics to
relaxor ferroelectric sates was observed. In the range 0≤x≤0.1, the temperature of dielectric
peak Tm is independence of the frequency, indicating the normal ferroelectrics behavior. At
x=0.15, dielectric relaxation process with a broadening distribution of the permittivity
dielectric is observed.
Abstract: To prepare a novel gas sensor being able to recognize molecules, waterborne
poly(β-cyclodextrin-block-polydiethylene glycol hexandioic ester) (i.e., waterborne
β-CD-block-PDEA) was synthesized and filled with carbon black (CB). It was found that the
composites’ electric resistance remarkably changed when the composites were exposed to the vapors
of small size molecule solvents (including dichloromethane, chloroform and tetrahydrofuran, etc.).
However, almost no response could be detected in the vapors of large size molecule solvents (like
n-pentane, ethylbenzene and hexane). Besides, the responsiveness gradually decreased with
increasing molecular size of organic solvents. The results evidenced that the composites have
acquired considerable selective sensitivity towards gaseous analytes in terms of their molecular sizes.
β-cyclodextrin rather than polydiethylene glycol hexandioic ester played the leading role in this
aspect, which was explained from the viewpoint of host-gust chemistry. That is, the response
mechanism is mainly based on the molecular discrimination behavior of the host compounds. The
small analytes could be entrapped by the β-cyclodextrin cavity due to van der Waals force. On the
other hand, solvents’ permittivity also played an important role. The molecules with high permittivity
were difficult to enter the hydrophobic cavities. The present study demonstrated the composites could
serve as candidates for gas sensors capable of molecule discrimination.
Abstract: Dielectric elastomers are a class of electro-active polymers (EAPs) which have great
potentials to be used in smart composites. These materials with compliant electrodes are converters of
electrical energy to mechanical energy in order to produce external load and strain with good
efficiency. Electrode materials should typically have good compliancy so that undergo large strain
alongside the film, without producing any additional stress and constraint for the actuator. In the
present study, the effect of 4 different electrode materials (graphite filled silicone oil, silver filled
grease, graphite powder and electrically conductive silicone rubber) on the performance of dielectric
elastomer actuators has been studied. The principle of operation, the method of fabrication and test
method of planar actuators are discussed. We have also studied the effects of different driving
voltages and different prestrain values on the actuator response. Experimental results showed that
electrical conductivity, material compliancy, and compatibility with substrate in the electrode
materials are some of the important parameters affecting the actuator performance.
Abstract: Dielectric elastomers (DEs) could be considered as a new type of transducers. They can
convert electrical and mechanical energies in a bi-directional manner. In this work, the
electromechanical behavior of a DE diaphragmatic generator was investigated. Circular diaphragms
were fabricated using a prestretched DE film sandwiched between laminates of compliant electrodes.
A special chamber was used to apply pressure. Pressure-Volume characteristics of diaphragms were
measured to calculate elastic energy density. DC voltages were applied to the electrodes and the
generated voltages were measured. It was concluded that efficiency of generators was strongly
dependent on the amount of biased voltage, pre-straining level and applied pressures.