Architecture of Functionally Graded Ceramic Coatings Against Surface Thermal Fracture

1996 ◽  
Vol 118 (4) ◽  
pp. 522-528 ◽  
Author(s):  
B. D. Choules ◽  
K. Kokini
Keyword(s):  
Stress Relaxation ◽  
Thermal Fatigue ◽  
Thermal Protection ◽  
Fatigue Behavior ◽  
Multilayer Coating ◽  
Single Layer ◽  
Ceramic Coatings ◽  
Functionally Graded ◽  
Transient Temperature ◽  
Layer Coating

An analytical study was performed to study the effect of architecture on the initiation of surface cracking in multilayer ceramic coatings. Two modes of crack initiation were considered: 1) tension resulting from stress relaxation, and 2) cyclic thermal fatigue. Transient temperature distributions were determined using a finite difference technique, and stress distributions were calculated using a multilayer beam theory. The results showed that as more layers were added and as the ceramic coating became thinner, lower maximum surface stresses resulted during cooling after stress relaxation. Also, a thick eight layer coating had similar thermal fatigue behavior to a thin single layer coating. It was determined that a thick multilayer coating adds a significant amount of thermal protection when compared to a thin single layered coating.

Determining Elastic Modulus of Ceramic Coatings at Elevated Temperature Using Impulse Excitation Technology

2016 ◽  
Vol 680 ◽  
pp. 13-16 ◽  
Author(s):  
Chen Guang Wei ◽  
Yi Wang Bao ◽  
Xue Qiang Cao ◽  
Zhao Liu ◽  
Yuan Tian
Keyword(s):  
Elastic Modulus ◽  
Elevated Temperature ◽  
Single Layer ◽  
Ceramic Coatings ◽  
Coated Sample ◽  
Multilayer Coatings ◽  
Relative Method ◽  
Impulse Excitation ◽  
Novel Method ◽  
Layer Coating

Although elastic modulus of ceramic coatings at elevated temperature is difficult to measure, it was evaluated in this work simply by impulse excitation tests based on the relative method that need only the measured moduli of coated sample and substrate. This novel method was demonstrated to be valid not only for the single layer coating but also for multilayer coatings.

Hertzian Contact Analysis of Ceramic/Metal Functionally Graded Coating

2013 ◽  
Vol 787 ◽  
pp. 582-587 ◽  
Author(s):  
Xiao Hui Dong ◽  
Hong Wei Zhang ◽  
Lei Wang
Keyword(s):  
Shear Stress ◽  
Coating Thickness ◽  
Maximum Shear Stress ◽  
Multilayer Coating ◽  
Engineering Application ◽  
Single Layer ◽  
Element Model ◽  
Functionally Graded ◽  
Hertzian Contact ◽  
Graded Coating

A finite element model with functionally graded materials is established. Furthermore, the distributions of the maximum contact stresses on monolithic substrates under Hertz contact conditions have been analyzed. The effect of the coating thickness is obtained by single-layer coating systems. With increasing the coating thickness, the distribution of maximum radial stress is moved from the coating surface to coating/substrate interface. Meanwhile, the depth of maximum shear stress is moved away from the interface. The location of the maximum shear stress within the multilayer coating systems is not changed. The deformation of the model is more serious with the increase of the applied load.The results can provide some insights regarding the design of the graded coatings in the engineering application.

Application of Electrochemical Techniques in the Porosity Assessment of Electroless Coatings

2012 ◽  
Vol 557-559 ◽  
pp. 1848-1851
Author(s):  
Yang Xu ◽  
Yong Zou ◽  
Tao Luan
Keyword(s):  
Polarization Resistance ◽  
Chemical Method ◽  
Electrochemical Techniques ◽  
Multilayer Coating ◽  
Single Layer ◽  
Linear Polarization Resistance ◽  
Single Layer Coating ◽  
Electroless Coatings ◽  
Layer Coating ◽  
Better Than

Chemical and electrochemical techniques were applied to evaluate the porosity of various electroless coatings (single-layer coating, multilayer coating and ternary coating). The electrochemical techniques include linear polarization resistance and Tafel extrapolation method. The effects of these techniques were compared. It’s evident that electrochemical methods performed better than chemical method when they were applied to assess the porosities of coatings with very fine through pores.

Correlation of fatigue behavior and dynamic mechanical properties of hybrid composites of polypropylene/short glass fibers/hollow glass beads

2021 ◽  
pp. 089270572199319
Author(s):  
Gustavo B Carvalho
Keyword(s):  
Stress Relaxation ◽  
Flexural Strength ◽  
Relaxation Rate ◽  
Hybrid Composites ◽  
Fatigue Behavior ◽  
Glass Fibers ◽  
Glass Beads ◽  
Hollow Glass ◽  
Dynamic Mechanical ◽  
Short Glass

Ternary hybrid composites of Polypropylene (PP)/Short Glass Fibers (GF)/Hollow Glass Beads (HGB) were prepared using untreated and aminosilane-treated HGB, compatibilized with maleated-PP, and with varying total and relative GF/HGB contents. Static/short-term flexural strength properties data revealed, through lower flexural strength values, that the presence of untreated HGB particles induces to fiber-polymer interfacial decoupling at much higher extent than in the presence of aminosilane-treated HGB particles. This phenomenon is also evident when evaluating the data from displacement-controlled three-point bending fatigue tests. Monitored up to 106 cycles, the analyzed hybrid composites presented distinct performance relative to their fatigue stress relaxation rate: the lower the matrix-reinforcements’ interfacial adhesion, more pronounced the stress relaxation rate as a function of the number of fatigue cycles. Dynamic Mechanical Thermal Analysis (DMTA) results could successfully reveal the hybrid composites behavior at the microstructural level when they were submitted to both static flexural test and fatigue, depending on the degree of interfacial interactions between the polymer matrix of PP and the hybrid reinforcements of GF and HGB (with and without aminosilane surface treatment).

scholarly journals Vibration analysis of a sandwich cylindrical shell in hygrothermal environment

2021 ◽  
Vol 10 (1) ◽  
pp. 414-430
Author(s):  
Chunwei Zhang ◽  
Qiao Jin ◽  
Yansheng Song ◽  
Jingli Wang ◽  
Li Sun ◽  
...  
Keyword(s):  
Cylindrical Shell ◽  
Natural Frequency ◽  
Equations Of Motion ◽  
Single Layer ◽  
Functionally Graded ◽  
Sandwich Shell ◽  
Continuous Change ◽  
Multilayered Structures ◽  
Cylindrical Sandwich Shell ◽  
Vibrational Behavior

Abstract The sandwich structures are three- or multilayered structures such that their mechanical properties are better than each single layer. In the current research, a three-layered cylindrical shell including a functionally graded porous core and two reinforced nanocomposite face sheets resting on the Pasternak foundation is used as model to provide a comprehensive understanding of vibrational behavior of such structures. The core is made of limestone, while the epoxy is utilized as the top and bottom layers’ matrix phase and also it is reinforced by the graphene nanoplatelets (GNPs). The pattern of the GNPs dispersion and the pores distribution play a crucial role at the continuous change of the layers’ properties. The sinusoidal shear deformation shells theory and the Hamilton’s principle are employed to derive the equations of motion for the mentioned cylindrical sandwich shell. Ultimately, the impacts of the model’s geometry, foundation moduli, mode number, and deviatory radius on the vibrational behavior are investigated and discussed. It is revealed that the natural frequency and rotation angle of the sandwich shell are directly related. Moreover, mid-radius to thickness ratio enhancement results in the natural frequency reduction. The results of this study can be helpful for the future investigations in such a broad context. Furthermore, for the pipe factories current study can be effective at their designing procedure.

A study on the electromagnetic properties of graphite/bismuth/bismuth oxide-coated composites

2021 ◽  
pp. 004051752199434
Author(s):  
Yuanjun Liu ◽  
Yanfeng Yang
Keyword(s):  
Mechanical Property ◽  
Dielectric Constant ◽  
Bismuth Oxide ◽  
Control Variable ◽  
Single Layer ◽  
Polarization Property ◽  
Electromagnetic Properties ◽  
Shielding Effectiveness ◽  
Absorbing Property ◽  
Layer Coating

Coating is a commonly used process for the preparation of protective textiles. In this study, the absorbing coated composite material was prepared by a coating process, using plain weave polyester/cotton fabric as the base fabric, PU-2540 polyurethane as the binder, and graphite, bismuth and bismuth oxide as the functional particles. The effects of the content of functional particles and the ratio of functional particles on the dielectric constant, reflection loss, shielding effectiveness, and tensile strength of the single-layer coating composites were studied using the control variable method. The results showed that when the frequency was 1–1000 MHz, the real and imaginary parts of the dielectric constant, the tangential value of the loss angle, and the tensile value increased with the increase of the coating content, and the polarization, loss and attenuation property, and mechanical property of the electromagnetic wave were enhanced. When graphite, bismuth, and bismuth oxide was mixed at the ratio of 9:0:0 in weight, the polarization property was the best. When mixed at the ratio of 6:1:2 in weight, the loss performance and attenuation ability were the best. When mixed at the ratio of 6:3:0 in weight, the absorbing property and mechanical property were the best. When mixed at the ratio of 6:2:1 in weight, the shielding property was the best.

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