scholarly journals Investigating the Effect of Stepped Scarf Repair Ratio in Repaired CFRP Laminates under Compressive Loading

2020 ◽  
Vol 4 (4) ◽  
pp. 153
Author(s):  
Spyridon Psarras ◽  
Theodoros Loutas ◽  
Magdalini Papanaoum ◽  
Orestis Konstantinos Triantopoulos ◽  
Vasilis Kostopoulos
Keyword(s):  
Numerical Models ◽  
Compressive Loading ◽  
Composite Plates ◽  
Step Length ◽  
Critical Threshold ◽  
Cfrp Laminates ◽  
Threshold Size ◽  
Repair Patch ◽  
Parametric Studies ◽  
Strength And Stiffness

In this work the effectiveness of stepped repairs to damaged fiber reinforced composite materials is investigated by using previously validated numerical models which were compared with tested repaired composite plates. Parametric studies were carried out in order to assess the scarf ratio (i.e., step length to ply thickness ratio) influence on ultimate forces, displacements, stresses and stiffnesses. FE models with repair scarf ratios varying from the value of 20 to the value 60 with a step increase of 10 were developed. The numerical models allowed a direct comparison of the influence that the scarf ratio had to the strength and stiffness restoration of the repaired composite structure. The study verifies that the restoration of the strength of a damaged laminate depends largely on the size of the repair patch. Generally, the bigger the size of a patch, the stronger the repaired structure is, up to a critical threshold size. To maximize the strength restoration, it is advised that the number of steps in each patch are no less than the number of plies on the base laminate.

scholarly journals A Computational Approach to Solve a System of Transcendental Equations with Multi-Functions and Multi-Variables

Mathematics ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 920
Author(s):  
Chukwuma Ogbonnaya ◽  
Chamil Abeykoon ◽  
Adel Nasser ◽  
Ali Turan
Keyword(s):  
Numerical Models ◽  
Problem Formulation ◽  
Science And Engineering ◽  
Physical Systems ◽  
Engineering Problems ◽  
Parametric Studies ◽  
Independent Variable ◽  
Transcendental Equations ◽  
The Waves ◽  
Modelling Approach

A system of transcendental equations (SoTE) is a set of simultaneous equations containing at least a transcendental function. Solutions involving transcendental equations are often problematic, particularly in the form of a system of equations. This challenge has limited the number of equations, with inter-related multi-functions and multi-variables, often included in the mathematical modelling of physical systems during problem formulation. Here, we presented detailed steps for using a code-based modelling approach for solving SoTEs that may be encountered in science and engineering problems. A SoTE comprising six functions, including Sine-Gordon wave functions, was used to illustrate the steps. Parametric studies were performed to visualize how a change in the variables affected the superposition of the waves as the independent variable varies from x1 = 1:0.0005:100 to x1 = 1:5:100. The application of the proposed approach in modelling and simulation of photovoltaic and thermophotovoltaic systems were also highlighted. Overall, solutions to SoTEs present new opportunities for including more functions and variables in numerical models of systems, which will ultimately lead to a more robust representation of physical systems.

scholarly journals Adipocyte death triggers a pro-inflammatory response and induces metabolic activation of resident macrophages

2021 ◽  
Vol 12 (6) ◽  
Author(s):  
Andreas Lindhorst ◽  
Nora Raulien ◽  
Peter Wieghofer ◽  
Jens Eilers ◽  
Fabio M. V. Rossi ◽  
...  
Keyword(s):  
Inflammatory Response ◽  
Metabolic Activation ◽  
Degradation Process ◽  
Critical Threshold ◽  
Low Grade ◽  
Blood Monocytes ◽  
Threshold Size ◽  
Laser Injury ◽  
Reporter Mice

AbstractA chronic low-grade inflammation within adipose tissue (AT) seems to be the link between obesity and some of its associated diseases. One hallmark of this AT inflammation is the accumulation of AT macrophages (ATMs) around dead or dying adipocytes, forming so-called crown-like structures (CLS). To investigate the dynamics of CLS and their direct impact on the activation state of ATMs, we established a laser injury model to deplete individual adipocytes in living AT from double reporter mice (GFP-labeled ATMs and tdTomato-labeled adipocytes). Hence, we were able to detect early ATM-adipocyte interactions by live imaging and to determine a precise timeline for CLS formation after adipocyte death. Further, our data indicate metabolic activation and increased lipid metabolism in ATMs upon forming CLS. Most importantly, adipocyte death, even in lean animals under homeostatic conditions, leads to a locally confined inflammation, which is in sharp contrast to other tissues. We identified cell size as cause for the described pro-inflammatory response, as the size of adipocytes is above a critical threshold size for efferocytosis, a process for anti-inflammatory removal of dead cells during tissue homeostasis. Finally, experiments on parabiotic mice verified that adipocyte death leads to a pro-inflammatory response of resident ATMs in vivo, without significant recruitment of blood monocytes. Our data indicate that adipocyte death triggers a unique degradation process and locally induces a metabolically activated ATM phenotype that is globally observed with obesity.

Two Tiered Analysis of a CFRP Laminate Imbedded With Magnetostrictive Particles

2010 ◽  
Author(s):  
George Currie ◽  
Dustin Spayde ◽  
Oliver Myers
Keyword(s):  
Experimental Approach ◽  
Analytical Investigation ◽  
Experimental Investigations ◽  
Cfrp Laminate ◽  
Cfrp Laminates ◽  
Excitation Coil ◽  
Laminate Theory ◽  
Linear Sections ◽  
Strength And Stiffness ◽  
Fundamental Equations

The overall purpose of this research is to characterize the affects of imbedding magnetostrictive particles (MSP) in a CFRP laminate for the purpose of nondestructive evaluation. This paper details an investigation using an analytical and experimental approach. At the time of this publication, both the analytical and experimental investigations are in a preliminary stage and the results have not yet converged. The analytical investigation utilizes fundamental equations for the magnetomechanical properties of the MSP and classical laminate theory for the strength and stiffness of the CFRP laminate to obtain a model of the combination. It is assumed that the magnetomechanical relationship of the MSP layer is a function of the prestress acting on the layer. This relationship is nonlinear in nature but is broken down into a number of linear sections to facilitate analysis. This prestress acting on the MSP layer is a result of the CFRP laminate’s stiffness resisting the induced strain of the MSP layer. Classical laminate theory is used to obtain the value of the prestress as a function of this induced strain. As would be expected, this analysis becomes an iterative process. The induced strain is calculated based on a prestress level of zero. This strain is then used to calculate the amount of stress in the CFRP laminate which becomes the prestress value, and the process is repeated until convergence is reached. Unidirectional CFRP laminates are used in this analysis. The experimental approach involved testing a collection of composite beams imbedded with MSP using a scanner that surrounded the beams. The scanner was composed of an excitation coil and a sensing coil. A detailed schematic of the scanner is included in the paper showing the slide along which the scanner apparatus moved, and the sensing coil surrounded by the excitation coil. The samples used in this analysis were constructed from unidirectional prepreg carbon fiber with varying internal delaminations, ply orientations, and number of plies. A program was constructed that allowed the user to control the signal being output to the excitation coil as well as record data from the sensing coil. The results presented in this paper are not final and will be used to create a foundation for continuation of this research.

Numerical Analysis and Mechanical Properties of Nomex™ Honeycomb Core

2017 ◽  
Author(s):  
Yue Liu ◽  
Weicheng Gao ◽  
Wei Liu ◽  
Zhou Hua
Keyword(s):  
Compressive Strength ◽  
Cell Walls ◽  
Mechanical Response ◽  
Compressive Loading ◽  
Fe Model ◽  
Honeycomb Core ◽  
Practical Applications ◽  
Honeycomb Sandwich ◽  
Nomex Honeycomb ◽  
Strength And Stiffness

This paper presents an investigation on the mechanical response of the Nomex honeycomb core subjected to flatwise compressive loading. Thin plate elastic in-plane compressive buckling theory is used to analyze the Nomex honeycomb core cell wall. A mesoscopic finite element (FE) model of honeycomb sandwich structure with the Nomex honeycomb cell walls is established by employing ABAQUS/Explicit shell elements. The compressive strength and compressive stiffness of Nomex honeycomb core with different heights and thickness of cell walls, i.e. double cell walls and single cell walls, are analyzed numerically using the FE model. Flatwise compressive tests are also carried out on bare honeycomb cores to validate the numerical method. The results suggest that the compressive strength and compression stiffness are related to the geometric dimensions of the honeycomb core. The Nomex honeycomb core with a height of 6 mm has a higher strength than that of 8 mm. In addition, the honeycomb core with lower height possesses stronger anti-instability ability, including the compressive strength and stiffness. The proposed mesoscopic model can effectively simulate the crushing process of Nomex honeycomb core and accurately predict the strength and stiffness of honeycomb sandwich panels. Our work is instructive to the practical applications in engineering.

Numerical Testing and Validation of LVI on Composite Plates

2019 ◽  
Vol 957 ◽  
pp. 358-365
Author(s):  
Giuseppe Lamanna ◽  
Francesco Caputo
Keyword(s):  
Residual Life ◽  
Numerical Models ◽  
Laminated Composite ◽  
Composite Plates ◽  
Experimental Tests ◽  
Numerical Code ◽  
Experimental Comparison ◽  
Structural Behaviour ◽  
Numerical Tests ◽  
Impact Energies

Laminated composite plates are widely used in the aerospace field, the prediction of their residual life is a interesting challenge for research communities. Their structural behaviour could be affected by several rupture mechanisms due to exercise loading conditions. One of the most critical is the low velocities impacts with different impact energies. This paper deals with an experimental test program performed in order to validate a numerical model developed by using finite element method. All experimental tests were carried out under international standard ASTM D7136 while all numerical tests were carried out by use of a worldwide numerical code Abaqus®. Inter-laminar and intra-laminar rupture mechanisms were taken into account and special-purpose elements were used. Rupture criteria were implemented in the numerical models thanks to their functional ease; results of numerical-experimental comparison were presented and discussed.

Bending of Laminated Composite Plates

2015 ◽  
Vol 725-726 ◽  
pp. 667-673 ◽  
Author(s):  
Marina Rakočević ◽  
Nikolay Vatin
Keyword(s):  
Cross Section ◽  
Numerical Models ◽  
Single Layer ◽  
Laminated Composite ◽  
Composite Plates ◽  
Layered Composite ◽  
Laminated Composite Plates ◽  
Layerwise Theory ◽  
Geometrical Characteristics ◽  
Laminate Theory

In this work, there are presented overviews of theoretical and numerical models for defining the stress-strain state in the cross section of moderately thick and thick composite plates in case of bending. Layered composite plates are constructed by combination of layers of various materials and geometrical characteristics, wherein each of them has got a bearing capacity in previously defined directions. By applying Equivalent Single-layer Laminate Theory (or ESL theory) these layers' problems cannot be solved successfully. That is the reason to apply contemporary theories of plates, in literature known as Layerwise theories. At the end of this work, there are given numeric examples of applying Partial Layerwise Theory.

Failure Mechanisms of Composite Plates With a Circular Hole Under Remote Biaxial Planar Compressive Loads

1997 ◽  
Vol 119 (1) ◽  
pp. 56-64 ◽  
Author(s):  
A. R. Khamseh ◽  
A. M. Waas
Keyword(s):  
Failure Mechanisms ◽  
Compressive Loading ◽  
Infinite Plate ◽  
Laminated Composite ◽  
Composite Plates ◽  
Laminated Composite Plates ◽  
Biaxial Tests ◽  
Compressive Loads ◽  
Stress Raisers ◽  
Plate Width

We report the results of an experimental investigation carried out for the analysis of failure mechanisms in fibrous laminated composite plates containing stress raisers, in the form of circular cutouts, under static biaxial planar compressive loading (i.e., compression in the two inplane orthogonal directions). A series of biaxial tests were carried out with 48 ply graphite/epoxy composites of varying fiber orientation. In all cases, the hole diameter to plate width aspect ratio remained in a range suitable for infinite plate assumptions. Fiber microbuckling, fiber kink banding, and fiber/matrix debonding are identified as the dominant failure mechanisms.

scholarly journals The Effect of Local Fuse on Behavior of Concentrically Braced Frame by a Numerical Study

2018 ◽  
Vol 4 (3) ◽  
pp. 655 ◽  
Author(s):  
Ali Kachooee ◽  
Mohammad Ali Kafi ◽  
Mohsen Gerami
Keyword(s):  
Seismic Response ◽  
Numerical Study ◽  
Numerical Models ◽  
Compressive Loading ◽  
Braced Frames ◽  
Concentrically Braced Frames ◽  
Reduced Cross Section ◽  
Braced Frame ◽  
Concentrically Braced Frame ◽  
Concentrically Braced

The concentrically braced frames (CBFs) are one of the most widely used lateral load-resisting systems. Seismic performance of these structures has a weakness that is due to the brace buckling at a lower loading than the ultimate compressive loading capacity. In this paper, attempt is made to enhance the seismic response of CBFs through utilizing a local fuse. For this purpose, first the formulation of fuse area and length are presented. Then based on this formulation, several numerical models have been built and analyzed to examine the effect of implementing this fuse on seismic response of CBFs. From the analyses results, it is found that if the reduced cross-section fuse (RCF) is properly designed and also the end of brace is fixed, the CBFs with equal energy dissipation capacity, that are equipped with this fuse exhibit a better ductility than the customary CBFs.

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