Experimental Investigation of Damage Characteristics in Steel Honeycomb Sandwich Beams

2011 ◽  
Vol 675-677 ◽  
pp. 685-688
Author(s):  
Jie Lu ◽  
Guang Ping Zou ◽  
Bao Jun Liu
Keyword(s):  
Failure Modes ◽  
Failure Process ◽  
Sandwich Beams ◽  
Damage Initiation ◽  
Damage Characteristics ◽  
Damage And Failure ◽  
Honeycomb Sandwich ◽  
Bending Loads ◽  
Good Agreement

Honeycomb sandwich structures are generally designed to carry flexural loads. However, mechanical properties can be influenced by accidental impacts, or service conditions. Thus a nondestructive detection testing is desired for them. In contrast to many conventional nondestructive evaluation (NDE) techniques, acoustic emission (AE) technique permits continuous damage inspection, classification and identification of failure modes in real time. In this work the fracture process of steel honeycomb sandwich beams has been investigated by in-situ AE technique. Pre-cracks were made both for L-direction and W-direction specimens subjected to three-points bending loads. Damage initiation sites were observed in the vicinity of the crack tip. A series of curves among the AE hits, AE amplitude, AE energy and loading time were obtained. Damage characteristics were discussed based on the above parameters. The results indicate AE characteristic parameters can reflect the damage and failure process of specimens. A good agreement was found between the experimental and analytical results.

Experimental Investigation of Damage Characteristics in Steel Honeycomb Sandwich Beams

2010 ◽  
Vol 452-453 ◽  
pp. 557-560
Author(s):  
Jie Lu ◽  
Guang Ping Zou ◽  
Bao Jun Liu
Keyword(s):  
Failure Process ◽  
Sandwich Beams ◽  
Characteristic Parameters ◽  
Damage Initiation ◽  
Damage Characteristics ◽  
Damage And Failure ◽  
Honeycomb Sandwich ◽  
Bending Loads ◽  
Ae Counts ◽  
Good Agreement

In this work the fracture process of steel honeycomb sandwich beams has been investigate by situ acoustic emission(AE) technique. Pre-cracks were made both for L-direction and W-direction specimens subjected to out-plane three-points bending loads. Damage initiation sites were observed in the vicinity of the crack tip. A series of curves among the AE counts, AE hits, AE amplitude, AE energy and loading time were obtained. Damage characteristics were discussed based on the above parameters. The results indicate AE characteristic parameters can reflect the damage and failure process of specimens. A good agreement was found between the experimental and analytical results.

Numerical Simulation of Ring-Shape Rock Failure under Compressive Loading

2011 ◽  
Vol 378-379 ◽  
pp. 15-18
Author(s):  
Yong Bin Zhang ◽  
Zheng Zhao Liang ◽  
Shi Bin Tang ◽  
Jing Hui Jia
Keyword(s):  
Numerical Simulation ◽  
Fracture Process ◽  
Failure Modes ◽  
Failure Process ◽  
Compressive Loading ◽  
Orientation Angle ◽  
Crack Orientation ◽  
Ring Specimen ◽  
Ring Shape ◽  
Good Agreement

In this paper, a ring shaped numerical specimen is used to studying the failure process in brittle materials. The ring specimen is subjected to a compressive diametral load and contains two angled central cracks. Numerical modeling in this study is performed. It is shown that the obtained numerical results are in a very good agreement with the experiments. Effect of the crack orientation angle on the failure modes and loading-displace responses is discussed. In the range of 0°~40°, the fracture paths are curvilinear forms starting from the tip of pre-existing cracks and grow towards the loading points. For the crack orientation angle 90°, vertical fractures will split the specimen and the horizontal cracks do not influence the fracture process.

Strength Characteristics and Deformation Behavior of Aluminum Honeycomb Sandwich Plates under Three-Point Bending Loads

2005 ◽  
Vol 297-300 ◽  
pp. 1503-1509
Author(s):  
Hyoung Gu Kim ◽  
Nak Sam Choi
Keyword(s):  
Failure Modes ◽  
Skin Layer ◽  
Strength Characteristics ◽  
Sandwich Plates ◽  
Honeycomb Core ◽  
Three Point Bending ◽  
Honeycomb Sandwich ◽  
Aluminum Honeycomb ◽  
Deformation Behaviors ◽  
Bending Loads

The strength characteristics as well as local deformation behaviors of honeycomb sandwich composite (HSC) structures under three-point bending loads were investigated in consideration of various failure modes such as skin layer yielding, interface-delamination as well as shear deformation and local buckling in the core layer. Various types of aluminum honeycomb core and skin layer were used for this study. Their finite-element simulation was performed to analyze stresses and deformation behaviors of honeycomb sandwich plates. The results were very comparable to the experimental ones. Consequently, thicker skin layer, smaller cell size of honeycomb core and less delamiantion had dominant effects on the improvement in strength and deformation behaviors of honeycomb sandwich plates.

Plastics Sandwich Beams under Bending Loads of Short Duration

1967 ◽  
Vol 9 (5) ◽  
pp. 355-361 ◽  
Author(s):  
R. M. Ogorkiewicz ◽  
A. A. M. Sayigh
Keyword(s):  
Polyvinyl Chloride ◽  
Short Duration ◽  
Stress Function ◽  
Local Stress ◽  
Sandwich Beams ◽  
Stress Concentrations ◽  
Four Point Bending ◽  
Bending Loads ◽  
Uniformly Distributed Loads ◽  
Good Agreement

Design of plastics sandwich structures calls for methods of predicting their deformation under load, which were studied with particular reference to beams under three- and four-point bending and under uniformly distributed loads. A preliminary series of tests established the stress-strain characteristics of p.v.c. (polyvinyl chloride) and polyurethane core and rigid p.v.c. skin materials. Using stress function solutions deflections and skin strains of different beams of these materials were then calculated and compared with experimental results obtained with beams made of the same combinations of materials. Good agreement was found for loads of short duration within the limits imposed by local stress concentrations.

Fatigue Life Prediction Investigation on Steel Honeycomb Sandwich Beams at High-Temperature

2011 ◽  
Vol 488-489 ◽  
pp. 698-701
Author(s):  
Jie Lu ◽  
Guang Ping Zou ◽  
Yang Cao
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Deformation Monitoring ◽  
Sandwich Beams ◽  
Three Point Bending ◽  
Time Deformation ◽  
Stiffness Reduction ◽  
Honeycomb Sandwich ◽  
Number Of Cycles ◽  
Good Agreement

The aim of this work is to investigate the fatigue behaviors of the steel honeycomb sandwich beams at 400°C through three point bending experiments. A stiffness reduction approach was adopted which was further based on the interpolation by the empirical functions of experimental results. For load control fatigue experiments, the evolution relations between number of cycles and displacement were obtained through real-time deformation monitoring of the specimens. A method based on exponential function fit was adopted in the further analysis, whose coefficients depended on the material properties, loading levels and high temperature conditions. This approach allowed us to predict the high temperature fatigue life of specimens while avoiding a large number of experiments. The results showed that experimental and prediction results were in a good agreement.

scholarly journals MODELS FOR INTRALAMINAR DAMAGE AND FAILURE OF FIBER COMPOSITES - A REVIEW

2016 ◽  
Vol 14 (1) ◽  
pp. 1 ◽  
Author(s):  
Klaus Rohwer
Keyword(s):  
Failure Modes ◽  
Mutual Influence ◽  
Failure Process ◽  
Matrix Material ◽  
Fiber Composites ◽  
Fiber Direction ◽  
Shear Stresses ◽  
Fiber Failure ◽  
Damage And Failure ◽  
The Matrix

In order to fully exploit the potential of structures made from fiber composites, designers need to know how damage occurs and develops and under what conditions the structure finally fails. Anisotropy and inhomogeneity cause a rather complex process of damage development which may be one reason for an exceptionally large number of existing models. This paper intends to provide an overview over those models and give some hints about current developments. As such it is an updated version of a recent publication [1]. The survey is limited to laminates from unidirectional layers out of straight continuous fiber polymer composites under quasi-static loading. Furthermore, focus is laid on intralaminar damage.Many failure models smear out the inhomogeneity between fibers and the matrix. Simply limiting each stress component separately can lead to surprisingly good results as documented in the first World-Wide Failure Exercise. Interpolation criteria consider mutual influence of normal and shear stresses, predominantly through a quadratic failure condition. Traditionally one distinguishes between interpolation criteria and physically based ones. As an important physical effect the difference between fiber failure and inter-fiber failure is considered. Furthermore, stress invariants are taken as a basis, increased shear strength under compression is accounted for, and characteristic failure modes are captured. Fibers and the matrix material are characterized by a large disparity in stiffness and strength. Micromechanical models consider this inhomogeneity but suffer from the difficulty to determine relevant material properties. Compressive strength in fiber direction has attracted special attention. However, the role of kink band formation, which is observed in the failure process, seems to be not yet fully understood.In summary it must be concluded that despite the tremendous effort which has been put into the model development the damage and failure simulation of fiber composites are not in a fully satisfying state. That is partly due to lack of accurate and reliable test results. 

Atomic Layer Deposition of LiF and Lithium Ion Conducting (AlF3)(LiF)x Alloys Using Trimethylaluminum, Lithium Hexamethyldisilazide and Hydrogen Fluoride

2017 ◽  
Author(s):  
Younghee Lee ◽  
Daniela M. Piper ◽  
Andrew S. Cavanagh ◽  
Matthias J. Young ◽  
Se-Hee Lee ◽  
...  
Keyword(s):  
Lithium Ion ◽  
Atomic Layer ◽  
Mass Gain ◽  
Alloy Film ◽  
Ex Situ ◽  
X Ray ◽  
Layer Deposition ◽  
Ion Conducting ◽  
Good Agreement

<div>Atomic layer deposition (ALD) of LiF and lithium ion conducting (AlF<sub>3</sub>)(LiF)<sub>x</sub> alloys was developed using trimethylaluminum, lithium hexamethyldisilazide (LiHMDS) and hydrogen fluoride derived from HF-pyridine solution. ALD of LiF was studied using in situ quartz crystal microbalance (QCM) and in situ quadrupole mass spectrometer (QMS) at reaction temperatures between 125°C and 250°C. A mass gain per cycle of 12 ng/(cm<sup>2</sup> cycle) was obtained from QCM measurements at 150°C and decreased at higher temperatures. QMS detected FSi(CH<sub>3</sub>)<sub>3</sub> as a reaction byproduct instead of HMDS at 150°C. LiF ALD showed self-limiting behavior. Ex situ measurements using X-ray reflectivity (XRR) and spectroscopic ellipsometry (SE) showed a growth rate of 0.5-0.6 Å/cycle, in good agreement with the in situ QCM measurements.</div><div>ALD of lithium ion conducting (AlF3)(LiF)x alloys was also demonstrated using in situ QCM and in situ QMS at reaction temperatures at 150°C A mass gain per sequence of 22 ng/(cm<sup>2</sup> cycle) was obtained from QCM measurements at 150°C. Ex situ measurements using XRR and SE showed a linear growth rate of 0.9 Å/sequence, in good agreement with the in situ QCM measurements. Stoichiometry between AlF<sub>3</sub> and LiF by QCM experiment was calculated to 1:2.8. XPS showed LiF film consist of lithium and fluorine. XPS also showed (AlF<sub>3</sub>)(LiF)x alloy consists of aluminum, lithium and fluorine. Carbon, oxygen, and nitrogen impurities were both below the detection limit of XPS. Grazing incidence X-ray diffraction (GIXRD) observed that LiF and (AlF<sub>3</sub>)(LiF)<sub>x</sub> alloy film have crystalline structures. Inductively coupled plasma mass spectrometry (ICP-MS) and ionic chromatography revealed atomic ratio of Li:F=1:1.1 and Al:Li:F=1:2.7: 5.4 for (AlF<sub>3</sub>)(LiF)<sub>x</sub> alloy film. These atomic ratios were consistent with the calculation from QCM experiments. Finally, lithium ion conductivity (AlF<sub>3</sub>)(LiF)<sub>x</sub> alloy film was measured as σ = 7.5 × 10<sup>-6</sup> S/cm.</div>

scholarly journals Millisecond lattice gasification for high-density CO2- and O2-sieving nanopores in single-layer graphene

2021 ◽  
Vol 7 (9) ◽  
pp. eabf0116
Author(s):  
Shiqi Huang ◽  
Shaoxian Li ◽  
Luis Francisco Villalobos ◽  
Mostapha Dakhchoune ◽  
Marina Micari ◽  
...  
Keyword(s):  
Single Layer ◽  
High Density ◽  
Single Layer Graphene ◽  
Pore Density ◽  
Vacancy Defects ◽  
Carbon Gasification ◽  
Layer Graphene ◽  
Gas Molecules ◽  
Good Agreement

Etching single-layer graphene to incorporate a high pore density with sub-angstrom precision in molecular differentiation is critical to realize the promising high-flux separation of similar-sized gas molecules, e.g., CO2 from N2. However, rapid etching kinetics needed to achieve the high pore density is challenging to control for such precision. Here, we report a millisecond carbon gasification chemistry incorporating high density (>1012 cm−2) of functional oxygen clusters that then evolve in CO2-sieving vacancy defects under controlled and predictable gasification conditions. A statistical distribution of nanopore lattice isomers is observed, in good agreement with the theoretical solution to the isomer cataloging problem. The gasification technique is scalable, and a centimeter-scale membrane is demonstrated. Last, molecular cutoff could be adjusted by 0.1 Å by in situ expansion of the vacancy defects in an O2 atmosphere. Large CO2 and O2 permeances (>10,000 and 1000 GPU, respectively) are demonstrated accompanying attractive CO2/N2 and O2/N2 selectivities.

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