Composite Loss Factor Research Articles

Effects of PZT particle-enhanced ply interfaces on the vibration damping behavior of CFRP composites

In this study, vibration damping behavior of carbon fiber reinforced polymer composites was investigated when ply interfaces were enhanced by lead zirconate titanate (PZT) particles. The influence of particle loading and carbon black coating of particles was analyzed using the dynamic mechanical analysis. When plain PZT particles were distributed in the ply interfaces, the loss factor increased but suddenly dropped with increased particle loading, producing a threshold effect. As the loss factor represents the joule heat of electric current between PZT particles and carbon fibers, the sudden drop implies that there exists incomplete connectivity. To demonstrate the effect of incomplete connectivity, plain PZT particles were coated with carbon black of various weight fraction and the experiments were repeated. The results show there exists an optimal coating ratio of carbon black where the loss factor reaches its maximum value. When the optimal coating was applied to plain PZT particles, the loss factors of composites continuously increased, eliminating the threshold effect.

Study on Damping Properties of Fiber Reinforced Compositefor Stayed Cable

Fiber reinforced vinyl ester composites and fiber reinforced epoxy composites were prepared by the pultrusion method. Due to the extensive application of fiber reinforced composites, the temperature spectrum and frequency spectrum of loss factor for the composite were tested using dynamic mechanical analysis (DMA) equipment. The damping properties and damping mechanism of the composite were investigated and discussed at different temperatures and frequencies. The result indicates that the loss factor of the composites is increasing with the increase of the frequency from 0.1Hz to 2 Hz and decreasing with the decrease of the temperature from -20°C to 60°C. The loss factor of the carbon fiber composite is higher than that of the glass fiber for the same matrix. The loss factor of the vinyl ester composite is higher than that of the epoxy composite for the same fiber.

Sensitivity of Dielectric Properties to Wear Process on Carbon Nanofiber/High-Density Polyethylene Composites.

We examined the correlation of wear effects with dielectric properties of carbon nanofibers (CNFs; untreated and organosilane-treated)-reinforced high-density polyethylene (HDPE) composites. Wear testing for the nanocomposites over up to 120 h was carried out, and then, dielectric permittivity and dielectric loss factor of the polymer composites with the increased wear time were studied. Scanning electron microscope and optical microscope observations were made to analyze the microstructure features of the nanocomposites. The results reveal that there exist approximate linear relationships of permittivity with wear coefficient for the nanocomposites. Composites containing silanized CNFs with the sufficiently thick coating exhibited high wear resistance. The change in permittivity was more sensitive to the increased wear coefficient for the nanocomposites with lower wear resistance. This work provides potential for further research on the application of dielectric signals to detect the effects of wear process on lifetime of polymeric materials.

자기력이 자기유동 탄성체의 압축 및 동적 특성에 미치는 영향

자기화 분말 함유량과 분말의 배향, 그리고 자기력 세기를 함수로 한 자기유동 탄성체의 압축 및 동적특성에 대해 연구하였다. 시험편은 순수 실리콘과 분말이 불규칙 배향된 실리콘, 축 방향으로 배향된 실리콘 그리고 축 직각 방향으로 배향된 실리콘으로 구분하였다. 탄성체 내에 포함된 분말의 배향을 위해 복합 탄성체의 성형을 자기장 내에서 실시하였다. 압축 및 동적시험은 자기력이 없는 경우와 자기력의 크기를 다르게 제어하는 경우로 구분하여 수행되었다. 복합 탄성체의 탄성율 및 손실계수는 동일한 자기력 세기에서 분말 함유량의 증가에 따라 증가하였다. 축 방향으로 배향된 복합탄성체의 탄성율과 손실계수는 축 직각 방향 배향 혹은 불규칙 배향에 비해 높게 나타났다. The compressive and dynamic properties of magnetorheological elastomers were investigated as functions of magnetizable particle volume fraction, alignment of the embedded particle and magnetic force. The specimens consisted of pure and filled silicons with randomly dispersed, longitudinal and transverse aligned magnetizable particle chains. To align the embedded particles in the elastomer, the cross-linking of the elastomer composites took place in a magnetic field. The compression and dynamic tests in the absence and the presence of different magnetic forces were carried out. The modulus and loss factor of the elastomer composites increase with increasing volume fraction at the same magnetic force. The case of longitudinal alignment shows a high modulus and loss factor when compared to the case of transverse alignment or random dispersion.

Interphase Effect on Fiber-Reinforced Polymer Composites

A mathematical model has been developed for the prediction of elastic moduli of three-phase fiber-reinforced composite. This model considers composite materials consisting of three phases, namely, fiber, interphase and matrix, and incorporates the effect of fiber packing. In the present paper, the interphase is assumed to be a homogeneous and isotropic material. The elastic moduli E 11, E 22, G 12 and G 23 have been evaluated and damping coefficients η 11, η 22, η 12and η 23 have been predicted by application of a correspondence principle using this developed model. The effect of interphase volume fraction on loss factors has been evaluated. Prediction of elastic moduli and loss factors has been carried out with a weak and a strong interphase. The calculated results show that the interphase volume fraction and its properties have a very significant effect on loss factor of fiber-reinforced polymer composite. Evaluation of material properties based on the finite element method is presented using representative volume element approach. Results using the developed model are in good agreement with those obtained by FEM and other methods.

Fabrication, Testing, and Modeling of Carbon Nanotube Composites for Vibration Damping

In this research, carbon nanotube (CNT) composite with epoxy resin is fabricated. The dynamic properties of the nanotube composites are evaluated. A testing apparatus for obtaining dynamic properties of composites is set up, and measurement procedures are given. In particular, the loss factors together with stiffness are measured for the specimens with different CNT weight ratios. Experimental results show that CNT additive can provide the composite with several times higher damping as compared with pure epoxy. A composite unit cell model containing a single CNT segment is developed by using the finite element method. Composite loss factors are calculated based on the average ratio of the unit cell energy loss to the unit cell energy input. Calculated loss factors under different strain are compared with experimental data. With the validated model, a parametric study is subsequently performed. Parameters, such as CNT dimension and CNT alignment orientation, are studied. The factors that lead to higher composite damping capacity are identified.

Effects of compatibilizers and electron radiation on thermomechanical properties of composites consisting of five recycled polymers

The purpose of this article is to show the influence of two compatibilizers and an electron radiation dose on the storage modulus ( M′), loss modulus ( M″), and loss factor (tan δ) of composites made of blends of the following five recycled polymers: low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), and poly(ethylene terephthalate) (PET). The aim of both adding a compatibilizer and applying high-energy electron radiation, with doses of up to 300 kGy, to the blends was to enhance their mechanical properties and, at the same time, to investigate the possibility of using these procedures for recycling plastic waste. As compatibilizers, styrene-ethylene/butylene-styrene elastomer grafted with maleic anhydride (SEBS- g-MA) and trimethylol propane trimethacrylate (TMPTA) were utilised. They were added in the amounts of 10 and 1 wt%, respectively. It was found that SEBS- g-MA and PS were thermodynamically immiscible with the remaining components of the composites at temperatures ranging from −20 to +150 °C, and that both the addition of TMPTA and the application of the electron radiation insignificantly affected the phase transition temperatures and the loss factor. On the other hand, a significant increase in the tan δ values upon the addition of SEBS- g-MA and/or rise in temperature were observed.

Carboxyl‐terminated butadiene acrylonitrile rubber/epoxy polymer alloys as damping adhesives and energy absorbable resins

AbstractCarboxyl‐terminated butadiene acrylonitrile (CTBN) liquid rubber/epoxy (diglycidyl ether of bisphenol‐A: DGEBA) / diamino diphenyl methane (DDM) resins, in which CTBN was 60 wt % as the major component, were formulated to evaluate the damping and adhesive properties. In cases where acrylonitrile (AN) was 10∼18 mol % as copolymerization ratio in CTBN, the blend resins showed micro‐phase separated morphologies with rubber‐rich continuous phases and epoxy‐rich dispersed phases. The composite loss factors (η) for steel laminates, which consisted of two steel plates with a resin layer in between, depended highly on the environmental temperature and the resonant frequencies. On the other hand, in the case where AN was 26 mol % in CTBN, the cured resin did not show clear micro‐phase separation, which means the components achieve good compatibility in nano‐scale. This polymer alloy had a broad glass‐transition temperature range, which resulted in the high loss factor (η > 0.1) for the steel laminates and excellent energy absorbability as the bulk resin in a broad temperature range. Also the resin indicated high adhesive strengths to aluminum substrates under both shear and peel stress modes. The high adhesive strengths of the CTBN/epoxy polymer alloy originated in the high strength and the high strain energy to failure of the bulk resin. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Vibration Damping on Graphite and KEVLAR(R)Composites Using Piezoceramic Powder Coatings: A Review

Some researchers have studied passive vibration damping using thin hybrid layer(s) of magnetostrictive powder coatings on a wide gamut of composite laminates. Although these magnetostrictive materials can be used for damping of thin flexible structural systems, in practice their use is limited in the domain of microwave spacecraft antenna applications because of electromagnetic interference (EMI) and electromagnetic coupling (EMC) issues at higher transmit and receive radio frequencies (RFs). Ultra-lightweight, high-frequency satellite reflectors made of high specific stiffness/high specific strength graphite and KEVLARcomposites, with stringent precision design requirements with respect to (w.r.t.) the root mean square surface error; pick up post-launch microvibrations in the deployed condition because of the movement of the three-axis gyros of the spacecraft or because of altitude correction exercises along with steep thermal gradients in the space domain. These vibrations at elevated temperatures need to be damped out, particularly in the passive domain, without affecting the overall stability of the spacecraft. Therefore, it is proposed to use particularly non-magnetic, thin hybrid piezoceramic powder coating(s) on one side of the graphite and KEVLAR® composites to cater for the microvibration suppression issue of the spacecraft reflectors. Moreover, at elevated temperatures, the adhesion of thin layers of piezoceramic materials on graphite and KEVLAR® composites also becomes an important issue, which needs to be addressed separately and has been reviewed at length. Therefore, in this paper, an attempt has been made to thoroughly review and investigate experimentally the use of the surface activation technique of RF plasma corona on composites along with coatings of thin hybrid layer(s) of high-sensitivity ferroelectrically soft, non-magnetic piezoelectric ceramic material for achieving passive vibration damping benefits on KEVLAR® and graphite composites with embedded KEVLAR® flexcore at varying temperatures. The surface activation has been performed using the plasma-etching approach to obtain improved adhesion of the piezoceramic material with composites at elevated temperatures. KEVLAR® and graphite composites were treated with RF plasma to modify the surface properties such that they contribute to the adhesion enhancement between plasma-treated polymer surfaces and the piezoceramic material coatings. We have referred to American Society for Testing and Materials (ASTM) standards for the finalization of test specimen sizes for the experimental work. Strain-dependent material damping in the thin piezoceramic passive layers on KEVLAR® and graphite composites leads to a typical nonlinear behavior at varying temperatures. Therefore, an Oberst vibrating beam technique has been chosen for experimentation on a cantilever specimen made of graphite and KEVLAR® in order to estimate the composite loss factor at elevated temperatures. The thin hybrid layer(s) of non-magnetic piezoceramic materials when coated on KEVLAR® and graphite substrates (on one side only) have given improved results w.r.t. passive structural damping at elevated temperatures with almost negligible weight penalty; this is with practically no EMI/EMC issues when tested separately for Ku-band frequencies at the Space Applications Centre, Indian Space Research Organization, Ahmedabad. The encouraging results, w.r.t. the enhanced passive damping at resonant frequencies for piezoceramic powder coated high specific stiffness/high specific strength graphite and KEVLAR® composites at elevated temperatures, may make the present investigation and review on piezocoated composites a possible candidate for high-frequency applications in future w.r.t. the microvibrations experienced in orbit by the reflectors of today's sophisticated Earth observation satellites, which are designed for stringent pointing accuracies and resolutions.

Dynamic-mechanical analysis and SEM morphology of wood flour/polypropylene composites

A study was conducted to investigate the effects of compatibilizers, including Maleic anhydride grafted polypropylene (MA-PP) and maleic anhydride grafted ethylene-propylene-diene copolymer (MA-EPDM), on wood-flour/polypropylene (WF/PP) composites. WF/PP composites were prepared by direct extrusion profiles using a twin-screw/single-screw extruder system. DMA analysis showed that the loss factor of composites decreased and the storage modulus improved in the presence of MA-PP, which indicated much better interfacial adhesion between the PP matrix and wood flour filler than in the absence of compatibilizer. Morphological feature based on SEM observation showed that MA-PP and MA-EPDM improved the dispersion of the wood particles in the plastic matrix. MA-EPDM is a soft segment, although it improved the interfacial adhesion, storage modulus decreases with adding of MA-EPDM. As compatibilizer of wood-flour/polypropylene composites, both DMA analysis and SEM feature proved that MA-PP was superior to MA-EPDM.

Dielectric analysis of VGCNF reinforced polyethylene composites

Dielectric analysis was performed on vapor grown carbon nanofiber reinforced high density polyethylene (HDPE) composites. The dielectric parameters (permittivity, loss factor, tan δ and ionic conductivity) of pure HDPE and composites were obtained in a frequency range of 0.01–10 5 Hz and temperature range of 35–120 °C. The dielectric properties of pure HDPE are slightly dependent on temperature and frequency. Permittivity values decreased slightly with frequency and temperature while changes in loss factor and dissipation factor (tan δ) were negligible. The dielectric properties of the composites showed a strong dependence on nanofiber content, testing frequency and temperature. Permittivity, loss factor and tan δ increased with the increase of nanofiber content and decreased with increasing temperature and frequency. Percolation phenomenon was observed in the dielectric analysis, similar to the percolation in electrical conductivity studies. The threshold value for permittivity and loss factor was ≈15 wt% VGCNF. The ionic conductivity of the composites increased with frequency.

Aeroelastic characteristics of cylindrical hybrid composite panels with viscoelastic damping treatments

Supersonic flutter analysis of cylindrical composite panels with structural damping treatments has been performed using the finite element method based on the zig-zag layerwise shell theory. The natural frequencies and loss factors of cylindrical viscoelastic composites are computed considering the effects of transverse shear deformation. And Kumhaar's modified piston theory is applied for the calculation of aerodynamic forces. The flutter of cylindrical composite panels is analyzed considering structural damping effect. With respect to aeroelastic stabilities, various damping characteristics of unconstrained layer, constrained layer, and symmetrically co-cured sandwich laminates are compared with those of an original base panel.

Electromagnetic and microwave absorbing properties of multi-walled carbon nanotubes/polymer composites

The preparation and characterization of CNTs/polymer (PET, PP, PE and varnish) composites were studied for microwave absorption applications in the range of 2–18 GHz. The results indicated the position of reflectivity peak moves to a lower frequency and the loss factors of composites increase with increasing CNTs concentrations. When CNTs concentration was above 4 wt%, there was a sharp increase of loss tangent. 4 wt% CNTs/PET and 8 wt% CNTs/varnish composites had considerable absorbing peak at 7.6 GHz, 15.3 GHz and achieved maximum absorbing value of 17.61 dB, 24.27 dB, respectively. In addition, the frequencies range for absorbing values exceeding 5 dB of CNTs/(PET, PP, varnish) composites are 13 GHz, 10 GHz and 6 GHz, respectively. The microwave absorption of CNTs composites can be mainly attributed to the dielectric loss rather than magnetic loss.

Effects of Interfacial Friction on the Damping Characteristics of Composites Containing Randomly Oriented Carbon Nanotube Ropes

This article presents a model for describing the damping characteristics of uniaxially stressed polymeric composites filled with randomly oriented single-wall nanotube (SWNT) ropes. A close-packed lattice consisting of seven nanotubes in hexagonal array is used to present the nanoropes. The composite is described as a three-phase system composed of a resin, a resin sheath acting as a shear transfer zone, and SWNT ropes. The concept of ‘stick-slip’ motion caused by frictional contacts is proposed to describe the load transfer behavior between individual nanotubes and between a nanotube rope and a sheath. The results of the analytical study show that both the Young’s modulus and the loss factor of the composite are sensitive to stress magnitude. Also, to show the inter-tube sliding effects due to nanotube aggregation, the Young’s moduli and the loss factors of composites filled with aligned SWNTs, aligned nanoropes, and randomly oriented nanoropes are compared.

ガラス織物強化ＳＤＲ制振材料の開発とその性能評価

Materials with both of high modulus and high damping properties are necessary in many industrial fields. Super damping rubber (SDR) has high damping properties, but it has some disadvantages in mechanical properties. In this paper, a series of glass fabric reinforced polyurethane super damping rubber materials (GFRR) were developed with high strength and high damping properties for the wide use of vibration reduction. The mechanical properties, such as tension, peeling and shearing of bonding interface, were investigated, which are much superior than SDR. For the application in vibration reduction, the composite loss factor was measured by the mechanical impedance method with a free-layer damping system, while the damping properties of viscoelastic layers were conducted by the dynamic mechanical analysis (DMA). Using the RKU model, the dependences of temperature and thickness ratio of composite loss factor were analyzed. The agreement between the experiment and the analysis suggests that the composite loss factor can be predicted with a good accuracy by RKU model.

海島構造を有する高分子系複合材料の巨視的損失係数のマイクロメカニックス解析(S07-4 複合材料II,S07 メゾスケールにおける先進材料の力学と強度・機能評価)

Macroscopic loss factor and shear modulus of a sea-island type polymer-based composite is calculated by using the equivalent inclusion method combined with the Mori-Tanaka theorem. The influences of the loss factor and the shear modulus of the particle on the macroscopic loss factors and shear modulus of the composite are examined under the shear applied stress. Consequently, an aspect ratio of the particles influences on both of the macroscopic loss factor and the shear modulus of the composite. Moreover, it is found that an optimum range of shear modulus of the particles exists for the maximum value of the macroscopic loss factor of the composite in the case of any aspect ratio of the particles.

Dynamic mechanical properties and interphase fiber/matrix evaluation of unidirectional glass fiber/epoxy composites

Storage modulus, loss modulus, and loss factor of unidirectional fiber composites of epoxy resin with glass fiber were determined with a Perkin Elmer DMA-7 equipment in three point bending mode. The fibers were coated with two different types of epoxy resins and the relationship between the thickness of coating and the composite viscoelastic properties were determined. A simple micromechanical model was used to analyze the data.

Styrene‐ethylene/butylene‐styrene blends for improved constrained‐layer damping

AbstractThe influence on the adhesion to some metal surfaces and the damping properties of various modified styrene‐ethylene/butylene‐styrene (SEBS) materials was evaluated. Modification of the different phases of the SEBS with resins was shown to have a large effect on the damping properties of the polymers, which were evaluated by dynamic mechanical analysis (DMA). A small amount of maleic anhydride grafted onto the EB block was found to lead to a significant improvement in the adhesion of the polymer to some metal surfaces without affecting the damping properties of the polymers. The results of the DMA tests on the polymers were used to calculate the composite loss factor (CLF) for a steel laminate, which consisted of two steel plates with a polymeric layer in between, according to the theory proposed by Ross, Ungar, and Kerwin. The calculated results were compared with the measured CLFs determined in vibrating beam tests (VBTs). The agreement between the calculated and measured values was quite fair, provided that the DMA values used for the calculations were recalculated to the actual higher frequencies used in the VBTs, using the time–temperature superposition principle. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2865–2876, 2001

Analytical modeling of damping at micromechanical level in polymer composites reinforced with coated fibers

Theoretical models using theory of elasticity, finite-element, and mechanics-of-materials formulations for characterizing the damping loss factor of composites with coated fiber reinforcement are described. The theoretical models are validated through comparison with experimental damping results conducted on composites having coated fibers as reinforcement. Explicit micromechanics equations are presented in order to define the damping and stiffness of unidirectional coated fiber composites under longitudinal normal (LN), transverse normal (TN), transverse shear (TS) and longitudinal shear (LS) loading conditions. Since shear deformation is essential for viscoelastic damping in polymers, and large shear strains are generated near the fiber/matrix interface in composites, it is shown that the use of a viscoelastic polymer coating on the fibers is an effective way of improving damping in such composites. A strain-energy approach was implemented with both a closed-form theory-of-elasticity solution and finite-element numerical simulations in order to carry out the analysis.

Viscoelastic composite materials for noise reduction and damage tolerance

This paper describes the concept of viscoelastic composites and how their dynamic physical characteristics may be exploited for ship applications where high vibrational damping and damage tolerance is a requirement. A mathematical model is used to describe the effect of fibre alignment on viscoelastic composite dynamic Young's Moduli and loss factors. The model, supported by experimental validation, requires the dynamic physical properties of the matrix resin for the range of operational temperatures and frequencies of interest. The model predicts that the resulting loss factor of a fibre reinforced viscoelastic resin composite behaves in an anisotropic fashion, however, damping optimisation may be achieved in two different ways dependant on the angle of fibre alignment. The implications of these findings and how the fibre alignment in a viscoelastic composite may be exploited for noise free ship and submarine machinery rafts are also discussed. Empirical studies on viscoelastic composites of this type using a drop weight impact tester have shown that their damage tolerance is superior to conventional glass reinforced polyester GRP. Although a theoretical analysis has not been made, it is implied that the viscoelastic nature of the matrix resin and its optimisation over the typical damaging impact frequencies is an important factor in absorbing the impact energy in much the same way as it is for absorbing vibrational energy. In this case the impact impluse is considered to be one particular extreme form of vibrational source. Provided the impact force can do work on the matrix, the energy will be absorbed by it if the viscoelastic nature of matrix is correct with little or no resulting damage to the composite.