MODULATION OF OPTICAL RADIATION BY MAGNETOMECHANICAL OSCILLATIONS IN THREE-LAYER COMPOSITE STRUCTURES

2015 ◽  
Vol 74 (3) ◽  
pp. 199-206
Author(s):  
I.V. Linchevsky
Keyword(s):  
Composite Structures ◽  
Optical Radiation ◽  
Layer Composite

Buckling failure of compressive loaded hard layers in flexible devices

2004 ◽  
Vol 843 ◽  
Author(s):  
Piet C.P. Bouten ◽  
Marcel A.J. van Gils
Keyword(s):  
Composite Structures ◽  
Compressive Strain ◽  
Thin Layers ◽  
Ambient Conditions ◽  
Flexible Devices ◽  
Layer Composite ◽  
Base Polymer ◽  
Buckling Failure ◽  
Inorganic Layers

ABSTRACTSubstrate materials for flexible devices are multi-layer composite structures. On top of a base polymer functional inorganic layers such as permeation barriers and conductive layers are applied. Due to the thermal mismatch between polymer and inorganic layer, the layer is compressive loaded at ambient conditions. A characteristic failure mode, occurring with compressive loaded thin layers, is buckling failure. The interface between adjacent layers fails locally, and the thin top layer bends outwards. The buckles have a characteristic width and height. These sizes are used to analyse the compressive strain, present in the layer before failure, and the adhesion quality of the failed interface. A buckle map is introduced to guide this analysis.

Thermal Performance Measurements of Thermal Interface Materials Using the Laser Flash Method

2007 ◽  
Author(s):  
Vinh Khuu ◽  
Michael Osterman ◽  
Avram Bar-Cohen ◽  
Michael Pecht
Keyword(s):  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Sink ◽  
Composite Structures ◽  
Laser Flash ◽  
Flash Method ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Layer Composite ◽  
Interface Materials

Thermal interface materials are used to reduce the interfacial thermal resistance between contacting surfaces inside electronic packages, such as at the die-heat sink or heat spreader-heat sink interfaces. In this study, the change in thermal performance was measured for elastomeric gap pads, gap fillers, and an adhesive throughout reliability tests. Three-layer composite structures were used to simulate loading conditions encountered by thermal interface materials in actual applications. The thermal resistance of the thermal interface material, including contact and bulk resistance, was calculated using the Lee algorithm, an iterative method that uses properties of the single layers and the 3-layer composite structures, measured using the laser flash method. Test samples were subjected to thermal cycling tests, which induced thermomechanical stresses due to the mismatch in the coefficients of thermal expansion of the dissimilar coupon materials. The thermal resistance measurements from the laser flash showed little change or slight improvement in the thermal performance over the course of temperature cycling. Scanning acoustic microscope images revealed delamination in one group of gap pad samples and cracking in the putty samples.

Study of the Design Representation Methods for the Optimization of Multi-Layer Composite Structures

2017 ◽  
Author(s):  
Hongyi Xu ◽  
Junqi Yang ◽  
Ching-Hung Chuang ◽  
Zhenfei Zhan
Keyword(s):  
Composite Structure ◽  
Composite Structures ◽  
Structure Optimization ◽  
Optimization Methods ◽  
Optimization Strategy ◽  
Root Cause ◽  
Design Representation ◽  
Layer Composite ◽  
Low Efficiency ◽  
The Impact

The purpose of multi-layer composite structure optimization is to find the optimal composite layout, such that superior structure performances and lightweight can be achieved. However, the existing optimization methods have a low efficiency when applied to the multi-component, multi-layer composite structure. Such low efficiency is caused by the high dimensionality and the inherent shortcomings of the existing design representation methods. In this work, two composite layout representation methods are compared to better understand their impacts on optimization. The root cause of the low efficiency is identified, and its influences are also quantified using three metrics. Furthermore, a new Representation-Switch Optimization (RSO) strategy is proposed. This strategy improves the search efficiency by switching the design representation methods during the optimization process. Three benchmark studies, two mathematical examples and one real engineering example, are conducted to demonstrate the impact of design representation methods on the optimization results, as well as the effectiveness of the proposed optimization strategy.

scholarly journals Behavior to Dynamic Loads of Multi-layer Composite Structures

2019 ◽  
Vol 56 (2) ◽  
pp. 460-465 ◽  
Author(s):  
Victor Geanta ◽  
Ionelia Voiculescu ◽  
Tudor Chereches ◽  
Teodora Zecheru ◽  
Liviu Matache ◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
Composite Structures ◽  
Basic Element ◽  
Steel Plates ◽  
Maximum Speed ◽  
Backing Plate ◽  
Layer Composite ◽  
Proposed Model ◽  
The Impact ◽  
Empirical Material

The explosive effect and high velocity penetration of the ballistic projectiles of various sizes, design and compositions, on impact with different targets (armors composed of a combination of different metals) are complex. Both practical experiments and mathematical modeling of the phenomena associated to the interaction projectile-target are required to estimate their effect or to design more efficient projectiles and armor. In this study, the basic element of the simulation model is an incendiary projectile of caliber 7.62 mm with medium piercing power, launched with a maximum speed of 750 ms-1 on the multi-material target, which contains 4 different layers assembled into a ballistic cassette made of aluminum. The purpose of this ballistic cassette is to ensure a better contact and handling of multi-layer materials. The proposed model was calculated using mathematical modeling and empirical material constants to describe the nonlinear transitory impact process. Mathematical simulation of the impact between the projectile and target during impact shows that the projectile moves sequentially through the ballistic package, causing perforation, plastic deformation and heating, the resulting fragments being then expelled into the space around the target. The model indicates that the projectile will penetrate the front aluminum plate, as well as the AlCrFeCoNi and steel plates, but will be stopped by the aluminum backing plate. The real impact tests carried out using the ballistic cassette at dynamic impact with the 7.62mm incendiary projectile confirm the model assumptions, which prove the capacity of the composite model to safely stop the projectile.

Efficient Reduced Simulation of Shell Structures With a Full Description of the Thickness: Application to Composites

2012 ◽  
Author(s):  
Etienne Pruliere
Keyword(s):  
Composite Structures ◽  
Computation Time ◽  
Full Description ◽  
Layered Shell ◽  
Shell Elements ◽  
Layer Composite ◽  
Plane Space ◽  
Out Of Plane ◽  
Separated Representation ◽  
3D Solid

Numerical simulations of composite structures are generally performed using multi-layered shell elements in the context of the finite elements method. This strategy has numerous advantages like a low computation time and the capability to reproduce the comportment of composites in most of cases. The main restriction of this approach is that it has only a coarse description of strain and stresses variations in the thickness. This approximation is no more valid when increasing the thickness, near the boundary and loading conditions and when non linear phenomena like delamination occurs in the thickness. This paper explores an alternative to shell computation using the Proper Generalized Methods based on a separated representation. The idea is to solve the full 3D solid problem separating the in-plane and the out-of-plane spaces. Practically, a classical shell mesh is used to describe the in-plane geometry and a simple 1D mesh is used to deal with the out-of-plane space. This allows to represents complex fields in the thickness without the complexity and the computation cost of a solid mesh which is particularly interesting when dealing with multi-layer composite.

scholarly journals TECHNOLOGICAL ASPECTS OF CREATING A FIBER-OPTIC NON-DESTRUCTIVE TESTING OF SANDWICH COMPOSITE STRUCTURES

2019 ◽  
pp. 24-29 ◽  
Author(s):  
M. Yu. Fedotov ◽  
O. N. Budadin ◽  
S. O. Kozel’skaya
Keyword(s):  
Control System ◽  
Composite Structure ◽  
Optical Method ◽  
Composite Structures ◽  
Fiber Optic ◽  
Fiber Optic Sensors ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Layer Composite ◽  
Non Destructive

The results of research on the formation of the system of built-in non-destructive testing of linings of composite three-layer structures by an optical method using fiber-optic sensors based on fiber Bragg gratings are presented. The features of creating an input/output zone for fiber-optic sensors as applied to three-layer composite structures are studied. Recommendations for ensuring the integrity and optimal functioning of the fiber-optic monitoring system as applied to a real three-layer composite structure are formulated. The following is shown. The process of creating an integrated control system of three-layer composite structures by an optical method using integrated fiber-optic sensors includes a number of operations to form a topology and to ensure the output of fiber-optic sensors from composite claddings in a single technological cycle of manufacturing the structure according to the standard technological process without significantly adjusting it, which is extremely important in relation to serial technologies. When developing the technology of integrating fiber-optic sensors into a three-layer composite structure, it was experimentally shown that from the point of view of survivability and preservation of the efficiency of the embedded control system, it is necessary to fulfill a number of requirements for the placement and output of fiber-optic sensors taking into account the characteristics of manufacturing, machining, and operation designs. Thus, it is advisable to place fiber optic sensors in the casings at least 5 mm from the intended edge of the structure, at least 2 layers from the outer surface of the structure and not less than 5 layers from the honeycomb core. The fiber bend radius should be at least 30 mm to prevent mechanical burst and sharp bending of the signal when it is bending. Fiber optic sensors are recommended to be placed between layers with a reinforcement scheme in the direction of the fiber optic sensor, however placement is also allowed between the fiber sensors and one layer with a different direction of reinforcement, while in order to prevent fractures, computation fiber optic sensors overlap is unacceptable, thus, between crossover fiber-optic sensors must be at least 2 layers of prepreg.

Dual-Band Linear Polarization Transformer with Diode-Like Asymmetric Transmission Based on Composite Metamaterial

2016 ◽  
Vol 848 ◽  
pp. 351-356 ◽  
Author(s):  
Yong Zhi Cheng ◽  
Bo He ◽  
Chen Jun Wu ◽  
Rong Zhou Gong
Keyword(s):  
Linear Polarization ◽  
Composite Structures ◽  
Ring Resonators ◽  
Dual Band ◽  
Tunneling Effect ◽  
Asymmetric Transmission ◽  
Layer Composite ◽  
Optical Isolators ◽  
Incident Waves ◽  
Sub Wavelength

A dual-band linear polarization transformer with diode-like asymmetric transmission using a three-layer composite metamaterial was proposed and investigated numerically. The proposed three-layer composite metamaterial was comprised of two layers of asymmetric split-ring resonators and a sub-wavelength cross structures sandwiched symmetrically between these layers. By introducing the sub-wavelength cross structure into the asymmetric chiral metamaterial, an electromagnetic wave tunneling effect formed for the incident waves. Thus, the transmissions in the composite structures can be strongly modified, one of the two off-diagonal cross-polarized transmission (txy) of the Jones matrix is enhanced while all the others (txx, tyy, and tyx) are suppressed extremely at resonances. This present design for enhancing asymmetric transmission via polarization conversion can be used as many novel devices, such as optical isolators, asymmetric wave splitters, and circulators.

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