Excellent Damping Properties Research Articles

Preparation and characterization of tetrapod-shaped ZnO whisker filled polyurethane cross-linked epoxy/polyurethane damping composites

A novel kind of damping composite was prepared, which consisted of the tetrapod-shaped ZnO whisker and polyurethane cross-linked epoxy/polyurethane. The dynamic mechanical properties of these materials were investigated by dynamic thermal analysis. Results indicated that the effective damping temperature range (tan δ > 0.3) was obviously broadened from 33.7°C to 178.8°C due to the formation of graft interpenetrating polymer network. With addition of tetrapod-shaped ZnO whisker, the maximal value of damping peak was improved to 1.44 for the increase of the internal friction. The morphological studies proved the existence of partial phase separation, and it was also observed that uniformly dispersed tetrapod-shaped ZnO whiskers were tightly implanted into the polymer matrix. The thermal stability and the tensile strength of composite were improved by the incorporation of tetrapod-shaped ZnO whisker. The results revealed that morphology of graft interpenetrating polymer network and addition of tetrapod-shaped ZnO whisker could provide excellent damping properties for the polymer matrix composite.

Vibration Damping in Ni-Mn-Ga/PU Polymer Composites

Ni-Mn-Ga ferromagnetic shape memory alloy is mainly focused from the class of active materials be- cause of their large field induced strain. They exhibit strains up to 10% with respect to the applied magnetic field through twin boundary motion in the martensite phase. This is the main advantage of this material which could over- come the frequency bound of the conventional shape memory alloys. Ni-Mn-Ga FSMAs show much large field-induced strain at low frequencies than do other active materials such as piezoelectrics or magentostrictors. When the twin boundaries are moving back and forth, the hysteresis connected to this motion provides vibration damping part of the damping bases on the magnetoelastic properties of the materials. The excellent damping properties of Ni-Mn-Ga alloys are bonded with the correct polymer matrix makes possible to develop new damping materials which are effective, less expensive and easier to form than bulk Ni-Mn-Ga. They can suit well to be used in the correct site for effective damp- ing in special engineering applications. In this article, we have prepared the composite materials and reported its basic characterization and the damping behavior of composite materials.

Multifunctional nanocomposite coating for wind turbine blades

In this study, multifunctional carbon nanofiber (CNF) paper-based nanocomposite coating was developed for wind turbine blades. The importance of vibration damping in relation to structural stability, dynamic response, position control, and durability of wind turbine blades cannot be underestimated. The vibration damping properties of the nanocomposite blades were significantly improved and the damping ratio of the nanocomposite increased by 300% compared to the baseline composite. In addition, the CNF paper-based composite exhibited good impact-friction resistance, with a wear rate as low as 1.78×10−4mm3/Nm. The nanocomposite also shows the potential to improve the blockage of water from entering the nanocomposite, being a superhydrophobic material, with a contact angle higher than 160.0°, which could improve the longevity of a wind turbine blade. Overall, multifunctional nanocomposite coating material shows great promise for usage with wind turbine blades, owing to its excellent damping properties, great friction resistance, and superhydrophobicity.

Numerical Simulation of Embedded and Co-Cured Composite Damping Structure under Low Velocity Impact

Embedded and co-cured composite damping structure is a novel damping processing structure, which possesses excellent damping properties and mechanical performances. In this paper, explicit dynamic analysis software LS-DYNA is employed to simulate low velocity impact on embedded co-cured composite damping structure panels. To illustrate the validity of modeling and calculation method, the simulation results are compared with the experimental data. And the results show that the impact resistance of embedded co-cured composite damping structure is much better than composite panel without damping material.

ICONE19-43187 Development of real time sensor for under sodium viewer

For the commercialization of the sodium cooled FBR system, it is desirable to develop a plant concept that has economic competitiveness compatible with the LWR system and excels in safety. Since it is difficult to perform inspection and maintenance of the core internals at FBR, such as the reactor vessel inner wall and the core support structure, measures have been taken to ensure safety and reliability by allowing a sufficiently large margin in the design reducing the burden of inspection and maintenance. To date due to problems such as the effect of radiation penetrating from the reactor core, the opacity and high chemical activity of sodium, and the fact that the inspection of reactor vessel of the FBR is performed at a high temperature, approximately 200 degree C, to avoid freezing of sodium, no method of inspecting structures inside the reactor vessel has been developed. In this study, aims to experimentally produce a real-time sensor which is used for the underwater and under-sodium test to demonstrate their applicability to the FBR system. The real-time sensor would be a piezoelectric element type sensor with a resolution of approximately 2.0mm, a resolution of sufficient quality to allow for the identification of deformation, the failure or dropping of components, and an image processing time per one image of approximately 0.5 second. Concerning the backing material, aluminum titanate (alumatite), wollastonite and hexagonal boron nitride were selected for the first screening. Based on the test result, alumatite that has an excellent damping property was finally selected for the trial production of the sensor element. We have designed and made 256 channel matrix-arrayed sensor and high speed processing system. It was shown that the real-time sensor was achieved about 2.0mm resolution and about 0.5 seconds/frame signal processing time, and succeeded taking the first under-sodium movie of the world.

The influence of modified VER on PU/VER IPN

PurposeThe aim of the paper is to develop a method to block hydroxyl groups of epoxy acrylate (AAEP) in vinyl ester resin (VER) and to study the influence of modified VER on polyurethane/(VER) interpenetrating polymer network (PU/VER IPN).Design/methodology/approachThe hydroxyl groups of AAEP in VER were blocked via different methods. Infra‐red spectroscopy was adopted to study the influence of the reagents, reaction temperature and feed molar ratio on the blocking effect of hydroxyl groups and the optimised technological parameters were determined. The PU/VER IPN and PU/modified VER IPN were prepared by simultaneous interpenetrating of VER (mixture of AAEP and butyl methacrylate with the mass ratio of 2/1) or modified VER and synthesised PU in their laboratory. The microstructure, dynamic mechanical properties and mechanical properties of PU/VER IPN and PU/modified VER IPN were compared.FindingsThe results showed that compared to unmodified IPN, because the hydroxyl groups in VER were blocked and no chemical cross‐linked structure existed between the two networks, the modified IPN showed dual‐continuous microsturcture with larger phase domain sizes between 20 and 50 nm. The effect damping temperature range of modified IPN was broadened and its damping performance was improved. The mechanical strength of modified IPNs decreased and their break elongation increased evidently.Practical implicationsThe PU/modified VER IPN with excellent damping properties can be used in the applications where reduction of vibration and noise is desired.Originality/valueThe PU/modified VER IPN, in which no chemical cross‐linked structure existed between the two networks, was novel and its damping performance was improved and excellent.

Novel Eucommia ulmoides Gum-based Damping Materials for Multicomponent Latex Interpenetrating Polymer Networks

This work describes a series of novel Eucommia ulmoides gum (EUG)-based damping materials with excellent damping properties by using the interpenetrating polymer network (IPN) method for the first time; this is an innovative application of EUG. The novel core-shell structure of an EUG-based multicomponent latex interpenetrating polymer network (LIPN) can be controlled by selecting a suitable initiator system, emulsification method, and polymeric sequence and by regulating the miscibility among the components. The damping properties and morphology of multicomponent LIPNs were investigated by dynamic mechanical analysis (DMA) and transmission electron microscope (TEM) in order to reveal the relationship between structure and performance. The results show that some LIPNs that use EUG as the seed in the multicomponent core-shell structure have a high damping factor (tanδ) at a broader temperature range. For example, the EUG/PS/PBA LIPN (1/1/1 by weight) possesses excellent damping properties; its temperature range for tanδ>0.3 extends to almost 130°C. EUG-based LIPNs, particularly the trinary EUG-based LIPNs are novel damping materials with good potential for development.

形状記憶ポリマー／ＣＦＲＰハイブリッド積層板の曲げおよび振動特性の評価

Although fiber reinforced plastics (FRP) are often used for structural components and functional materials, the vibration reduction for FRP materials is still difficult. The hybrid construction of FRP is well known as more effective for the improvement of this property. In this paper, in order to improve damping characteristics of FRP materials, carbon fabric reinforced shape memory polymer (SMP/CFRP) hybrid laminates are developed. The bending and damping property is investigated by the three-point bending test and mechanical impedance method. The influence of lamination position and contents of SMP in hybrid laminates on mechanical property is discussed. The theoretical formula for bending modulus and bending strength was proposed, and the validity was confirmed by experiment. The results show that the developed hybrid laminates has high bending modulus and excellent damping properties.

マグネシウム箔のプレス成形

The use of magnesium and its alloys, which have excellent vibration damping properties, as materials for parts of acoustic equipment, such as the diaphragm used in speakers or tweeters, is now being considered. However, a foil of 50-100μm thickness is required for acoustic equipment, and it is considered difficult to press such a foil made of magnesium and its alloys into the desired shapes. In particular, magnesium foil, which must be processed through warm forming, is expected to be more difficult to form than other metal foils. In this study, we initially used an AZ31 magnesium alloy foil and a pure magnesium foil, which has a higher vibration damping property than an alloy foil, to evaluate the formability in the warm forming of these foils using two press forming methods: stretch forming and deep drawing. Next, on the basis of the examination results, we proposed two forming methods for the manufacture of a dome-shaped diaphragm for a tweeter and succeeded in forming a diaphragm made of pure magnesium foil using these methods.

Damping properties and morphology of polyurethane/vinyl ester resin interpenetrating polymer network

A series of polyurethane/vinyl ester resin simultaneous and gradient interpenetrating polymer networks (PU/VER IPN and gradient IPN), cured at room temperature, were synthesized by introducing acrylic esters as VER’s comonomers. The effects of thermodynamic factor, kinetic factor, component ratio and gradient techniques on their damping properties were studied by DMA. It was found that the damping properties of general PU/VER (St) IPN with styrene (St) as VER’s comonomer are improved by introducing acrylic esters instead of St. When the relative polymerization rates of the networks are close, 80:20, 70:30 and 60:40 PU/VER (BMA) IPNs with butyl methacrylate (BMA) as VER’s comonomer have excellent damping properties. The gradient IPN with better damping properties than simultaneous IPNs was obtained by adjusting the gradient techniques. The tan δ values of the gradient IPN with the time interval of 3 h and the component ratios of 50:50–60:40–70:30 are higher than 0.3 from −57 °C to higher than 90 °C, and its tan δ values are higher than 0.5 from −36 to 54 °C. The results of EDX revealed that the gradient structure is formed in transition regions of gradient IPN. The results detected by TEM and AFM showed that the phase ranges of PU/VER (BMA) IPNs and gradient IPN obtained are both in nanometer scale. Furthermore, the relationship of microstructure and damping properties was studied.

The Damping Property of Magnetic Rubber Dampers with a Constraining Layer. 1st Report. Derivation of the Equation of Loss Factor Based on the Analysis of Flexural Vibration of Beam.

Viscoelastic damping materials with a constraining layer have excellent damping properties, but they have a weighty drawback that many works, such as preliminary treatment of adhesive surfaces and hold of viscoelastic damping materials till adhesive is completely stiffened, are required. To overcome this drawback, magnetic rubber dampers with a constraining layer (MRDC), which are composed of two layers-a magnetic rubber layer and a constraining steel layer-have been developed. They are easy to be fixed onto steel objects due to the attractive force of magnetic rubber layer. The damping property of MRDC is substantially caused by the friction loss which arises between the magnetic rubber layer and the steel object. The equation of loss factor of a beam with a sheet of MRDC is derived by taking the friction loss into account to analyze the flexural vibration of the beam.

Study on the properties and application of epoxy resin/polyurethane semi-interpenetrating polymer networks

Damping properties of epoxy resin/polyurethane (EP/PU) semi-interpenetrating polymer networks (IPNs) were studied by the dynamic mechanical analysis (DMA) method. It shows that the semi-IPNs have excellent damping properties at ordinary temperature. The maximum value of tan δ is about 1 when the weight composition of EP/PU is 70/30. Tensile tests also indicate that the system has good tensile strength and elongation at break at this ratio. The effects of structure on the properties of the semi-IPNs are discussed. Applied to the cavitation corrosion resistant coating, the semi-IPNs show good cavitation corrosion resistance. © 1996 John Wiley & Sons, Inc.

DAMPING BEHAVIOR OF Fe-Ni-Mn TERNARY ALLOYS

Abstract Fe-Ni-Mn alloys show good damping characteristics when they have an appropriate combination of composition relating to the stacking fault energy. The absorption mechanism of vibration energy may be in a dislocation configuration accompanied by stacking faults that extends over two slip planes to be crossed each other. The configuration should be maintained on a balance between back and forth stresses developed on each plane, so that, if the matrix were subjected to any external stress, two partials surrounded a stacking fault must be constricted to a perfect'dislocation, then it cross slips and rc-dissociates on the other plane. This mechanism can act as a dash pot and absorbs vibration energy. Experiments showed that the alloys with 3 to 7 mass % Ni and 11 to 15 mass % Mn possessed the most excellent damping properties which were evaluated by logarithmic decrement δ.

Chlorosulfonated polyethylene: A versatile polymer for damping acoustic waves

Viscoelastic polymers are used extensively in acoustics to reduce structureborne, airborne, and waterborne sound fields. Applications include free or constrained layers used to damp vibrating structures, as the compliant layer in tuned dampers, and as closed cell foams used to render water-filled tanks nonreverberant. In addition to the wide frequency ranges usually imposed in these applications, environmental conditions are frequently severe: temperatures may vary by more than an order of magnitude; solvents may exist which degrade many polymers; and the polymers may be constantly exposed to ozone and ultraviolet radiation. Chlorosulfonated polyethylenes are sufficiently versatile to be used under all of these conditions, can be easily fabricated into films, sheets, and closed cell foams, and offer excellent damping properties over the full spectrum of frequency/temperature combinations encountered during most damping applications, as will be shown. Discussed will be the dependence of the damping properties, such as the elastic modulus, loss factor, and glass transition temperature, upon the chlorine content and the amount and type of filler.