Non-Contact Laser Ultrasonic Inspection for Cryogenically Introduced Interlayer Defects in Epoxy-Based Composites

2002 ◽  
Author(s):  
Vikram Vedantham ◽  
Anirudh Thummalapalli ◽  
Baozhong Yang ◽  
C. Steve Suh
Keyword(s):  
Instantaneous Frequency ◽  
Bulk Material ◽  
Ultrasonic Inspection ◽  
Layered Composite ◽  
Constant Thickness ◽  
Layered Composites ◽  
Non Invasive ◽  
Frequency Components ◽  
Number Of Cycles ◽  
Reference Knowledge

Traditional transducer-based techniques for Non-Destructive Evaluation (NDE) are limited by fixed frequency-bandwidth for generation and sensing, and thus provide unsatisfactory resolution for certain types of material defects. Thermo-Acousto-Photonic NDE (TAP-NDE) is a proven alternative that is non-invasive and non-contact, and suited for real-time applications. This paper focuses on employing TAP-NDE to examine the presence of microcracks and fissures in multi-layered composites. Tests were performed on layered composite panels of specific epoxyresin composition and constant thickness to identify localized delaminations formed by subjecting the specimen to cryogenic cycling. Interrogation of the undamaged specimen using laser-generated broadband surface waves revealed a standard reference knowledge base, as seen in the instantaneous frequency-time domain. Tests were repeated after each specimen was subjected to a set number of cycles of liquid nitrogen cycling, which caused damages at the micron scale in the bulk material. Analyses showed changes in the time of wave arrival and absence of prominent high frequency components. Wave velocity and dispersion characteristics of the cycled specimen were altered. Thus, the specimen, on cryogenic cycling, was found to undergo a decrease in stiffness, which is speculatively the result of micro-voids, fissures or delaminations between layers. Hence, when combining with the basic notion of instantaneous frequency, TAP-NDE acts as an effective broadband generation and sensing technique, demonstrating feasibility and greater versatility for inspecting layered composites as against contemporary narrowband techniques.

Determination of the transverse shear stress in layered composites

2020 ◽  
Vol 86 (2) ◽  
pp. 44-53
Author(s):  
Yu. I. Dudarkov ◽  
M. V. Limonin
Keyword(s):  
Shear Stress ◽  
Transverse Shear ◽  
Composite Beam ◽  
Layered Composite ◽  
Equivalent Model ◽  
Shear Stresses ◽  
Transverse Shear Stress ◽  
Layered Composites ◽  
Laminate Composites ◽  
Transverse Shear Stresses

An engineering approach to estimation of the transverse shear stresses in layered composites is developed. The technique is based on the well-known D. I. Zhuravsky equation for shear stresses in an isotropic beam upon transverse bending. In general, application of this equation to a composite beam is incorrect due to the heterogeneity of the composite structure. According to the proposed method, at the first stage of its implementation, a transition to the equivalent model of a homogeneous beam is made, for which the Zhuravsky formula is valid. The transition is carried out by changing the shape of the cross section of the beam, provided that the bending stiffness and generalized elastic modulus remain the same. The calculated shear stresses in the equivalent beam are then converted to the stress values in the original composite beam from the equilibrium condition. The main equations and definitions of the method as well as the analytical equation for estimation of the transverse shear stress in a composite beam are presented. The method is verified by comparing the analytical solution and the results of the numerical solution of the problem by finite element method (FEM). It is shown that laminate stacking sequence has a significant impact both on the character and on the value of the transverse shear stress distribution. The limits of the applicability of the developed technique attributed to the conditions of the validity of the hypothesis of straight normal are considered. It is noted that under this hypothesis the shear stresses do not depend on the layer shear modulus, which explains the absence of this parameter in the obtained equation. The classical theory of laminate composites is based on the similar assumptions, which gives ground to use this equation for an approximate estimation of the transverse shear stresses in in a layered composite package.

scholarly journals Preparation and Properties of Layered SiC-Graphene Composites for EDM

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2916
Author(s):  
Ondrej Hanzel ◽  
Zoltán Lenčéš ◽  
Peter Tatarko ◽  
Richard Sedlák ◽  
Ivo Dlouhý ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Surface Layer ◽  
Positive Influence ◽  
Layered Composite ◽  
Layered Composites ◽  
Good Adhesion ◽  
Electric Discharge Machining ◽  
Layer Sequence ◽  
The Individual ◽  
Scratch Tests

Three and five-layered silicon carbide-based composites containing 0, 5, and 15 wt.% of graphene nanoplatelets (GNPs) were prepared with the aim to obtain a sufficiently high electrical conductivity in the surface layer suitable for electric discharge machining (EDM). The layer sequence in the asymmetric three-layered composites was SiC/SiC-5GNPs/SiC-15GNPs, while in the symmetric five-layered composite, the order of layers was SiC-15GNPs/SiC-5GNPs/SiC/SiC-5GNPs/SiC-15GNPs. The layered samples were prepared by rapid hot-pressing (RHP) applying various pressures, and it was shown that for the preparation of dense 3- or 5-layered SiC/GNPs composites, at least 30 MPa of the applied load was required during sintering. The electrical conductivity of 3-layered and 5-layered composites increased significantly with increasing sintering pressure when measured on the SiC surface layer containing 15 wt.% of GNPs. The increasing GNPs content had a positive influence on the electrical conductivity of individual layers, while their instrumented hardness and elastic modulus decreased. The scratch tests confirmed that the materials consisted of well-defined layers with straight interfaces without any delamination, which suggests good adhesion between the individual layers.

Ballistic Performance of TiC-TiB2 Composite Armour under the Impact of Long-Rod Tungsten Alloy Projectiles of 1.4 km · s-1

2013 ◽  
Vol 544 ◽  
pp. 310-315
Author(s):  
Xue Gang Huang ◽  
Zhong Min Zhao ◽  
Long Zhang
Keyword(s):  
Layered Composite ◽  
Tungsten Alloy ◽  
Ti Alloy ◽  
Impact Point ◽  
Layered Composites ◽  
Micro Hardness ◽  
Ballistic Performance ◽  
Long Rod ◽  
High Gravity Field ◽  
The Impact

Based on using combustion synthesis in high-gravity field to prepare the solidified TiC-TiB2 composites, the layered composites of the ceramic to Ti-6Al-4V at graded composition were achieved by fusion joint and atomic inter-diffusion between liquid TiC-TiB2 and Ti-6Al-4V substrate. The mechanical properties showed that the relative density, micro-hardness and fracture toughness of TiC-TiB2 ceramic layer measured 98.5%, 21.5 GPa and 13.5 ± 2.5 MPa • m0.5, respectively, and the shear strength at joint of TiC-TiB2 to Ti-6Al-4V measured 450 ± 25 MPa. By conducting DOP test to evaluate ballistic performance of the ceramic and layered-composite targets against long-rod KE projectiles at impact velocity of 1.4 km • s-1, it was obtained the mass efficiency 3.28 of the solidified TiC-TiB2 was achieved as the impact point of the projectile was nearby the centre of the target, whereas the mass efficiency 3.18 of the layered composite with the solidified ceramic to Ti-6Al-4V was also achieved even if the impact point of the projectile was at the edge of the target. By combining penetration damage of the targets with the dynamic behavior of the ceramic, it was obtained that the layered composite achieved by the joint of the solidified ceramic to Ti-6Al-4V not only improve ballistic performance of the ceramic, but also weaken the sensitivity of the ceramic target against the impact point of KE projectile by tearing the joint of the ceramic with Ti alloy to restrain formation and propagation of conical crack and fracture cone in the ceramic.

Concordia Transform-Based Current Analysis for Induction Motor Diagnosis

2013 ◽  
Vol 569-570 ◽  
pp. 481-488
Author(s):  
Jin Jiang Wang ◽  
Robert X. Gao ◽  
Ru Qiang Yan
Keyword(s):  
Induction Motor ◽  
Instantaneous Frequency ◽  
Low Cost ◽  
Experimental Studies ◽  
Current Analysis ◽  
New Approach ◽  
Non Invasive ◽  
Bearing Defects ◽  
Bearing Defect ◽  
Three Phase

This paper presents a new approach for bearing defect diagnosis in induction motor by taking advantage of three-phase stator current analysis based on Concordia transform. The current signature caused by bearing defect is firstly analyzed using an analytic model. Concordia transform is performed to extract the instantaneous frequency based on phase demodulation. The bearing defect feature is then identified via spectrum analysis of the variation of current instantaneous frequency. Both simulation and experimental studies are performed to demonstrate the effectiveness of proposed method in identifying bearing defects. The method is inherently low cost, non-invasive, and computational efficient, making it a good candidate for various applications.

PCA and ICA Based Prognostic Health Monitoring of Electronic Assemblies Subjected to Simultaneous Temperature-Vibration Loads

2017 ◽  
Author(s):  
Pradeep Lall ◽  
Tony Thomas
Keyword(s):  
Frequency Analysis ◽  
Health Monitoring ◽  
Instantaneous Frequency ◽  
Principal Component ◽  
Component Analysis ◽  
Time Frequency Analysis ◽  
Time Frequency ◽  
Strain Components ◽  
Frequency Components ◽  
Electronic Assemblies

This paper focusses on health monitoring of electronic assemblies under vibration load of 14 G until failure at an ambient temperature of 55 degree Celsius. Strain measurements of the electronic assemblies were measured using the voltage outputs from the strain gauges which are fixed at different locations on the Printed Circuit Board (PCB). Various analysis was conducted on the strain signals include Time-frequency analysis (TFA), Joint Time-Frequency analysis (JTFA) and Statistical techniques like Principal component analysis (PCA), Independent component analysis (ICA) to monitor the health of the packages during the experiment. Frequency analysis techniques were used to get a detailed understanding of the different frequency components before and after the failure of the electronic assemblies. Different filtering algorithms and frequency quantization techniques gave insight about the change in the frequency components with the time of vibration and the energy content of the strain signals was also studied using the joint time-frequency analysis. It is seen that as the vibration time increases the occurrence of new high-frequency components increases and further the amplitude of the high-frequency components also has increased compared to the before failure condition. Statistical techniques such as PCA and ICA were primarily used to reduce the dimensions of the larger data sets and provide a pattern without losing the different characteristics of the strain signals during the course of vibration of electronic assemblies till failure. This helps to represent the complete behavior of the electronic assemblies and to understand the change in the behavior of the strain components till failure. The principal components which were calculated using PCA discretely separated the before failure and after failure strain components and this behavior were also seen by the independent components which were calculated using the Independent Component Analysis (ICA). To quantify the prognostics and hence the health of the electronic assemblies, different statistical prediction algorithms were applied to the coefficients of principal and independent components calculated from PCA and ICA analysis. The instantaneous frequency of the strain signals was calculated and PCA and ICA analysis on the instantaneous frequency matrix was done. The variance of the principal components of instantaneous frequency showed an increasing trend during the initial hours of vibration and after attaining a maximum value it then has a decreasing trend till before failure. During the failure of components, the variance of the principal component decreased further and attained a lowest value. This behavior of the instantaneous frequency over the period of vibration is used as a health monitoring feature.

Fabrication, Structure and Properties of Aluminum-Aluminide Layered Composites

1996 ◽  
Vol 434 ◽  
Author(s):  
D. E. Alman
Keyword(s):  
Layered Structure ◽  
Hot Pressing ◽  
Tensile Tests ◽  
Layered Composite ◽  
Structure And Properties ◽  
Layered Composites ◽  
Heat Treated

AbstractThe fabrication of aluminum-aluminide layered composites by reactive bonding of elemental Al and Ni foils was investigated. It was observed that after hot-pressing, thin Ni foils were converted to NiAl. The as-processed Al-NiAl layered structure could be heat-treated to produce an equilibrium Al-Al3Ni layered composite. Tensile tests revealed that composites could be produced that failed in a “tough” manner and were stronger and stiffer than aluminum.

Alumina and Zirconia Based Layered Composites: Part 2 Fracture Response

2009 ◽  
Vol 412 ◽  
pp. 227-232 ◽  
Author(s):  
Zdeněk Chlup ◽  
Hynek Hadraba
Keyword(s):  
Residual Stresses ◽  
Crack Propagation ◽  
Bulk Material ◽  
Fracture Plane ◽  
Limiting Factor ◽  
Tension Stress ◽  
Angle Of Incidence ◽  
Layered Composites ◽  
Wide Range ◽  
Laminated Structures

Laminated materials are used for special applications where combination of properties of two components is needed. Ceramics is inherently brittle and above all superior properties (wear resistance, temperature durability, stiffness, low density and others) the brittleness is limiting factor for massive implementation in wide range applications. The laminated structure can be capable to overcome this handicap. Electrophoretic deposition (EPD) is the technique able to prepare ceramic laminated structures having strong interface between layers [1]. It is possible to prepare dense and crack free materials with tailored residual stresses controlled by layer thickness and deposition conditions by this technique. Crack propagation through layered composites based on Al2O3 and ZrO2 was studied. Cracks, produced by an indentation technique, propagated in direction to layer interfaces deflected towards the interface in the compressed layers and away from the interface in the layers containing tension stress [2,3]. Changes in the direction of crack propagation for the whole range of angles of incidence (0° - 90°) were described. The biggest change in the crack propagation was observed for the angle of incidence 45° for A/Z systems and was ca. 15°. The change in the crack propagation was independent on the level of residual stresses in the layers. Behaviour of indentation cracks observed in laminates under investigation was compared with the results obtained on standard SEVNB specimens having inclined the fracture plane with respect to the composite lamellar structure. This model condition helps to understand crack propagation in bulk material. All experimental work was supported by fractographical techniques enabling explanation of fracture micromechanism.

scholarly journals Torsion Dynamic Behaviour of the Ship Hull Made out of Layered Composites

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Ionel Chirica
Keyword(s):  
Composite Plates ◽  
Past Research ◽  
Layered Composite ◽  
Ship Hull ◽  
Scale Model ◽  
Behavioral Characteristics ◽  
Container Ship ◽  
Layered Composites ◽  
Dynamic Torsion ◽  
Software Code

This paper addresses the dynamic torsion behaviour of the ship hull with very large open decks. A short overview of the past research is presented, and several key findings and behavioral characteristics are discussed. In the paper, the author is focusing on the dynamic part of a new macroelement model used for torsion dynamic analysis of the ship hull made of composite materials. The numerical analysis (using two methods, one of them being a new proposed method) and experiments are developed on a simplified typical hull of a container ship. The torsion analysis is performed on a scale model of a container ship, made of layered composite plates, and the first 5 natural frequencies are determined. The results obtained with the proposed numerical method (software code TORS, made by the author) are compared with the results obtained with FE analysis and with the experiments done on the physical model.

scholarly journals Plasma coatings containing high-baring phases

2019 ◽  
Vol 64 (1) ◽  
pp. 35-43
Author(s):  
N. A. Rudenskaya ◽  
G. P. Shveykin ◽  
M. V. Rudenskaya
Keyword(s):  
Plasma Flow ◽  
Plasma Generator ◽  
Ceramic Materials ◽  
Layered Composite ◽  
Accelerated Cooling ◽  
High Wear Resistance ◽  
Layered Composites ◽  
Polymorphic Transformations ◽  
Temperature Plasma ◽  
Antifriction Properties

Results of comparative researches of the initial and processed in a plasma flow oxidic microcomposites, consisting of TiO2, SiO2, Al2O3, ZrO2, and plasma coverings from them – the materials which are characterized by amorphous and crystal structure and strengthened by ultradispersed phases of the stishovit, are presented. It is shown the influence of a type, structure and a way of processing of material (initial powder of different dispersion; the powder obtained in a plasma flow at the different modes and with the normal and accelerated cooling; a plasma layered composite) on the content of silicon oxides, aluminum and titanium, on the type of polymorphic transformations (anatase is found both in powders, and in coverings; the accelerated cooling of spheroids leads to growth of its contents in microcomposites) and also on feature of forming in ceramic materials of a high-bar phase – the stishovit (stishovit it is found only in coverings). It is established that increase in power of the plasma generator leads to increase in extent of amorphicity of plasma-layered composites. In the structure of layered composites three groups of the inclusions, combined by the composition, are revealed: two groups of aluminosilicates and inclusions on the basis of zirconium dioxide. Inclusions of the third group are characterized by two types of structures: homogeneous, consisting of zircon, and plated (with a kernel of dioxide of zirconium and a cover from zircon). The developed layered composites are characterized by high wear resistance, corrosion resistance and antifriction properties. In the conditions of low-temperature plasma at atmospheric pressure the stishovit-containing materials are obtained for the first time.

Indentation Mechanics for Micro- and Nano-Layered Composites

2008 ◽  
Author(s):  
G. Tang ◽  
Y.-L. Shen
Keyword(s):  
Composite Structure ◽  
Layered Composite ◽  
Material System ◽  
Layered Composites ◽  
The Finite Element Method ◽  
Diamond Indenter ◽  
Stress And Deformation ◽  
Deformation Patterns ◽  
Model Features ◽  
Multilayered Thin Films

The effect of micro- and nano-scale heterogeneity on the indentation behavior of the composite structure was studied numerically using the finite element method. The material system of concern is the aluminum (Al)/silicon carbide (SiC) multilayered thin films above the silicon (Si) substrate. The numerical model features the explicit composite structure indented by a conical diamond indenter within the axisymmetric simulation framework. Attention is devoted to the evolution of stress and deformation fields in the layered composite during the indentation loading and unloading processes. It was found that the layered composite, consisting of materials with distinctly different mechanical properties, results in unique deformation patterns. Significant tensile stresses can be generated locally along certain directions, which offers a mechanistic rationale for the indentation-induced internal cracking observed experimentally. The unloading process also leads to an expansion of the tension-stressed area, as well as continued plastic flow in parts of the Al layers. Implications of these numerical findings to the nanoindentation response of metal-ceramic laminates are discussed.

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