Parametric Study of Specific Buckling Load of Cylindrical Grid Stiffened Composite Shells

2012 ◽  
Vol 13 (1) ◽  
pp. 482-485 ◽  
Author(s):  
Hamid Shahsavari Alavijeh ◽  
Soroush Sadeghnejad ◽  
Mojtaba Sadighi
Keyword(s):  
Parametric Study ◽  
Buckling Load ◽  
Composite Shells ◽  
Cylindrical Grid

Numerical approaches to stability analysis of cylindrical composite shells based on load imperfections

2015 ◽  
Vol 32 (2) ◽  
pp. 498-518 ◽  
Author(s):  
Nikolay Asmolovskiy ◽  
Anton Tkachuk ◽  
Manfred Bischoff
Keyword(s):  
Composite Structures ◽  
Specific Pattern ◽  
Buckling Load ◽  
Perturbation Approach ◽  
Local Dynamic ◽  
Load Estimation ◽  
Composite Shells ◽  
Content Type ◽  
Global And Local ◽  
Dynamic Perturbation

Purpose – Current procedures of buckling load estimation for thin-walled structures may provide very conservative estimates. Their refinement offers the potential to use structure and material properties more efficiently. Due to the large variety of design variables, for example laminate layup in composite structures, a prohibitively large number of tests would be required for experimental assessment, and thus reliable numerical techniques are of particular interest. The purpose of this paper is to analyze different methods of numerical buckling load estimation, formulate simulation procedures suitable for commercial software and give recommendations regarding their application. All investigations have been carried out for cylindrical composite shells; however similar approaches are feasible for other structures as well. Design/methodology/approach – The authors develop a concept to apply artificial load imperfections with the aim to estimate as good as possible lower bounds for the buckling loads of shells for which the actual physical imperfections are not known. Single and triple perturbation load approach, global and local dynamic perturbation approach and path following techniques are applied to the analysis of a cylindrical composite shell with known buckling characteristics. Results of simulations are compared with published experimental data. Findings – A single perturbation load approach is reproduced and modified. Buckling behavior for negative values of the perturbation load is examined and a pattern similar to a positive perturbation load is observed. Simulations with three perturbation forces show a decreased (i. e. more critical) value of the buckling load compared to the single perturbation load approach. Global and local dynamic perturbation approaches exhibit a behavior suitable for lower bound estimation for structures with arbitrary geometries. Originality/value – Various load imperfection approaches to buckling load estimation are validated and compared. All investigated methods do not require knowledge of the real geometrical imperfections of the structure. Simulations were performed using a commercial finite element code. Investigations of sensitivity with respect to a single perturbation load are extended to the negative range of the perturbation load amplitude. A specific pattern for a global perturbation approach was developed, and based on it a novel simulation procedure is proposed.

Parametric study on the buckling load after micro-bolt repair of a composite laminate with delamination

2019 ◽  
Vol 215 ◽  
pp. 1-12 ◽  
Author(s):  
Gyu-Seok Kang ◽  
Byeong-Su Kwak ◽  
Hyeon-Seok Choe ◽  
Jin-Hwe Kweon
Keyword(s):  
Parametric Study ◽  
Composite Laminate ◽  
Buckling Load

PROBABILISTIC DESIGN OF AXIALLY COMPRESSED COMPOSITE CYLINDERS WITH GEOMETRIC AND LOADING IMPERFECTIONS

2010 ◽  
Vol 10 (04) ◽  
pp. 623-644 ◽  
Author(s):  
BENEDIKT KRIEGESMANN ◽  
RAIMUND ROLFES ◽  
CHRISTIAN HÜHNE ◽  
JAN TEßMER ◽  
JOHANN ARBOCZ
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Fourier Coefficients ◽  
Cylindrical Shells ◽  
Probabilistic Approach ◽  
Element Model ◽  
Buckling Load ◽  
Probabilistic Design ◽  
Composite Shells ◽  
Buckling Loads

The discrepancy between the analytically determined buckling load of perfect cylindrical shells and experimental test results is traced back to imperfections. The most frequently used guideline for design of cylindrical shells, NASA SP-8007, proposes a deterministic calculation of a knockdown factor with respect to the ratio of radius and wall thickness, which turned out to be very conservative in numerous cases and which is not intended for composite shells. In order to determine a lower bound for the buckling load of an arbitrary type of shell, probabilistic design methods have been developed. Measured imperfection patterns are described using double Fourier series, whereas the Fourier coefficients characterize the scattering of geometry. In this paper, probabilistic analyses of buckling loads are performed regarding Fourier coefficients as random variables. A nonlinear finite element model is used to determine buckling loads, and Monte Carlo simulations are executed. The probabilistic approach is used for a set of six similarly manufactured composite shells. The results indicate that not only geometric but also nontraditional imperfections like loading imperfections have to be considered for obtaining a reliable lower limit of the buckling load. Finally, further Monte Carlo simulations are executed including traditional as well as loading imperfections, and lower bounds of buckling loads are obtained, which are less conservative than NASA SP-8007.

Delamination Effects on Composite Shells

1990 ◽  
Vol 112 (3) ◽  
pp. 336-340 ◽  
Author(s):  
Fu-Kuo Chang ◽  
Zafer Kutlu
Keyword(s):  
Shear Fracture ◽  
Strain Energy Release ◽  
Analytical Investigation ◽  
Buckling Load ◽  
Composite Shells ◽  
Delamination Growth ◽  
Buckling Behavior ◽  
Post Buckling ◽  
Crack Tips ◽  
Updated Lagrangian

An analytical investigation was performed to study the effect of delamination on the response of cylindrical composite shells subjected to external loadings. It was of particular interest to determine the buckling load and the post-buckling behavior of externally pressurized cylindrical composite shells containing delaminations. An analytical model was developed that consists of a structural analysis for calculating the global deformations of the structures and a fracture analysis for determining the delamination growth in the structures. A nonlinear finite element code based on the updated Lagrangian formulation was developed for the model. Based on the results of calculations, it was found that delamination can significantly affect the buckling load and response of cylindrical composite shells subjected to externally pressurized loadings, depending upon the initial length and location of the delamination, ply orientation and laminate curvature. The calculated strain energy release rate at the crack tips indicates that delamination growth occurs in the wake of buckling due to Mode II shear fracture.

Buckling of Edge Damaged, Cylindrical Composite Shells

1989 ◽  
Vol 56 (1) ◽  
pp. 121-126 ◽  
Author(s):  
M. Sabag ◽  
Y. Stavsky ◽  
J. B. Greenberg
Keyword(s):  
Boundary Conditions ◽  
Axial Compression ◽  
Cylindrical Shells ◽  
Buckling Load ◽  
Composite Shells ◽  
Gradual Reduction ◽  
Critical Buckling Load ◽  
Anisotropic Composite ◽  
The Stability ◽  
Edge Damage

The stability of thin composite layered anisotropic cylindrical shells under axial compression is considered for the case of nonuniform boundary conditions. Such conditions are employed to model the situation where there is edge damage to the shell. The influence of weakening or a crack at an edge on the critical buckling load of a variety of single and multilayered shells is investigated. Results indicate that isotropic shells exhibit a rather sudden steep reduction in the critical buckling load for relatively small edge damage. However, some anisotropic composite shells may not be so sensitive and, in contrast, only a gradual reduction may be brought about by the edge damage. The degree of sensitivity to edge damage appears to be dependent, in some complex fashion, on the various geometric and physical shell parameters.

Parametric Study of Photovoltaic Thermal Solar Collector Using An Improved Parallel Flow

2020 ◽  
Vol 2 (1) ◽  
pp. 19-24
Author(s):  
Sakhr Mohammed Sultan ◽  
Chih Ping Tso ◽  
Ervina Efzan Mohd Noor ◽  
Fadhel Mustafa Ibrahim ◽  
Saqaff Ahmed Alkaff
Keyword(s):  
Thermal Conductivity ◽  
Energy Balance ◽  
Parametric Study ◽  
Solar Collector ◽  
Parallel Flow ◽  
Operating Conditions ◽  
Balance Equations ◽  
Conductivity Type ◽  
Pv Module ◽  
Sunny Weather

Photovoltaic Thermal Solar Collector (PVT) is a hybrid technology used to produce electricity and heat simultaneously. Current enhancements in PVT are to increase the electrical and thermal efficiencies. Many PVT factors such as type of absorber, thermal conductivity, type of PV module and operating conditions are important parameters that can control the PVT performance. In this paper, an analytical model, using energy balance equations, is studied for PVT with an improved parallel flow absorber. The performance is calculated for a typical sunny weather in Malaysia. It was found that the maximum electrical and thermal efficiencies are 12.9 % and 62.6 %, respectively. The maximum outlet water temperature is 59 oC.

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