Multiobjective Optimization of Fiber Composite Shells for Maximum Buckling Load and Imperfection Tolerance

Abstract The performance of thin-walled structures, which are endangered by buckling, is often strongly influenced by geometrical imperfections. It is impossible to know in advance the imperfections, which will be present in the real structure. Nevertheless, their influence has to be taken into account already at the design process. Attempts to identify characteristic imperfections due to specific manufacturing processes overcome this difficulty only partly, as they do not consider imperfections coming into existence after fabrication. The remedy is, to build imperfection tolerant structures. For that purpose, a simple means to measure imperfection tolerance is defined, and a multiobjective optimization formulation is proposed to design fiber composite shell structures, which simultaneously exhibit high imperfection tolerance and high buckling load. By example of axially compressed CFRP cylindrical shells first computational and experimental results are given to demonstrate the feasibility of the concept, and to identify needs for further research.

Linear buckling topology optimization of reinforced thin-walled structures considering uncertain geometrical imperfections

Structural and Multidisciplinary Optimization ◽

10.1007/s00158-020-02738-6 ◽

2020 ◽

Vol 62 (6) ◽

pp. 3367-3382

Author(s):

Yangjun Luo ◽

Junjie Zhan

Keyword(s):

Topology Optimization ◽

Thin Walled Structures ◽

Linear Buckling ◽

Experimental Nondestructive Test for Estimation of Buckling Load on Unstiffened Cylindrical Shells Using Vibration Correlation Technique

Shock and Vibration ◽

10.1155/2015/729684 ◽

2015 ◽

Vol 2015 ◽

pp. 1-8 ◽

Cited By ~ 8

Author(s):

Kaspars Kalnins ◽

Mariano A. Arbelo ◽

Olgerts Ozolins ◽

Eduards Skukis ◽

Saullo G. P. Castro ◽

...

Keyword(s):

Large Scale ◽

Numerical Models ◽

Cylindrical Shells ◽

Laser Scanner ◽

Experimental Tests ◽

Buckling Load ◽

Correlation Technique ◽

Thin Walled Structures ◽

Instability Point ◽

Nondestructive methods, to calculate the buckling load of imperfection sensitive thin-walled structures, such as large-scale aerospace structures, are one of the most important techniques for the evaluation of new structures and validation of numerical models. The vibration correlation technique (VCT) allows determining the buckling load for several types of structures without reaching the instability point, but this technique is still under development for thin-walled plates and shells. This paper presents and discusses an experimental verification of a novel approach using vibration correlation technique for the prediction of realistic buckling loads of unstiffened cylindrical shells loaded under axial compression. Four different test structures were manufactured and loaded up to buckling: two composite laminated cylindrical shells and two stainless steel cylinders. In order to characterize a relationship with the applied load, the first natural frequency of vibration and mode shape is measured during testing using a 3D laser scanner. The proposed vibration correlation technique allows one to predict the experimental buckling load with a very good approximation without actually reaching the instability point. Additional experimental tests and numerical models are currently under development to further validate the proposed approach for composite and metallic conical structures.

Stability and Vibration of Imperfect Column and Slender Web

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.969.328 ◽

2014 ◽

Vol 969 ◽

pp. 328-331

Author(s):

Ľuboš Šnirc ◽

Jan Ravinger

Keyword(s):

Residual Stresses ◽

Linear Theory ◽

Stiffness Matrix ◽

Natural Vibration ◽

Thin Walled Structures ◽

Thin Walled ◽

Non Destructive ◽

Structural Imperfections ◽

Lagrange Description

Using the geometric non-linear theory (The Total Lagrange Description) in dynamics we can establish the problem of the natural vibration of the structure including the effects of the structural and geometrical imperfections. The incremental stiffness matrix can take into account the residual stresses (structural imperfections) and the geometrical initial displacements (geometrical imperfections) as well. The behaviour of columns, frames and thin-walled structures is sensitive to imperfections. This theory and results can be used as a base for the non-destructive method for the evaluation of the level of the load and the imperfections.

A Simplified Method to Simulate Residual Stresses in Plates

10.20944/preprints202009.0129.v1 ◽

2020 ◽

Author(s):

José Manuel Gordo ◽

Gonçalo Teixeira

Keyword(s):

Residual Stresses ◽

Thermal Process ◽

Structural Strength ◽

Finite Element Models ◽

Welded Structures ◽

Thin Walled Structures ◽

Simplified Method ◽

Adequate Representation ◽

Welded structures are subjected to internal residual stress after manufacturing that may affect the structural strength and normally are associated with an increase on initial geometrical imperfections. This study presents a simplified method to generate an adequate representation of residual stresses on Finite Element models for structural analysis of thin-walled structures and other applications. The results obtained shown that the methodology proposed to introduce residual stresses is simple, accurate and efficient on the modulation of post-welding stresses and their pattern, thus it may be used for simulation of the thermal process.

Optimization of thin-walled structures with geometric nonlinearity for maximum critical buckling load using optimality criteria

Thin-Walled Structures ◽

10.1016/j.tws.2008.04.002 ◽

2008 ◽

Vol 46 (12) ◽

pp. 1319-1328 ◽

Cited By ~ 12

Author(s):

Peyman Khosravi ◽

Rajamohan Ganesan ◽

Ramin Sedaghati

Keyword(s):

Geometric Nonlinearity ◽

Optimality Criteria ◽

Buckling Load ◽

Critical Buckling Load ◽

Thin Walled Structures ◽

Material Design for Optimal Postbuckling Behaviour of Composite Shells

Materials ◽

10.3390/ma14071665 ◽

2021 ◽

Vol 14 (7) ◽

pp. 1665

Author(s):

Domenico Magisano ◽

Francesco Liguori ◽

Antonio Madeo ◽

Leonardo Leonetti ◽

Giovanni Garcea

Keyword(s):

Material Design ◽

Computational Design ◽

Discrete Models ◽

Composite Shells ◽

Imperfection Sensitivity ◽

Thin Walled Structures ◽

Solution Methods ◽

Thin Walled ◽

Optimal Material

Lightweight thin-walled structures are crucial for many engineering applications. Advanced manufacturing methods are enabling the realization of composite materials with spatially varying material properties. Variable angle tow fibre composites are a representative example, but also nanocomposites are opening new interesting possibilities. Taking advantage of these tunable materials requires the development of computational design methods. The failure of such structures is often dominated by buckling and can be very sensitive to material configuration and geometrical imperfections. This work is a review of the recent computational developments concerning the optimisation of the response of composite thin-walled structures prone to buckling, showing how baseline products with unstable behaviour can be transformed in stable ones operating safely in the post-buckling range. Four main aspects are discussed: mechanical and discrete models for composite shells, material parametrization and objective function definition, solution methods for tracing the load-displacement path and assessing the imperfection sensitivity, structural optimisation algorithms. A numerical example of optimal material design for a curved panel is also illustrated.

Multiobjective optimization for foam-filled multi-cell thin-walled structures under lateral impact

Thin-Walled Structures ◽

10.1016/j.tws.2015.03.031 ◽

2015 ◽

Vol 94 ◽

pp. 1-12 ◽

Cited By ~ 57

Author(s):

Hanfeng Yin ◽

Youye Xiao ◽

Guilin Wen ◽

Qixiang Qing ◽

Yufeng Deng

Keyword(s):

Multiobjective Optimization ◽

Lateral Impact ◽

Thin Walled Structures ◽

Foam Filled ◽

Comparison of theoretical approaches to account for geometrical imperfections of unstiffened isotropic thin walled cylindrical shell structures under axial compression

Thin-Walled Structures ◽

10.1016/j.tws.2015.02.019 ◽

2015 ◽

Vol 92 ◽

pp. 1-9 ◽

Cited By ~ 27

Author(s):

Linus Friedrich ◽

Theodor-Andres Schmid-Fuertes ◽

Kai-Uwe Schröder

Keyword(s):

Cylindrical Shell ◽

Axial Compression ◽

Shell Structures ◽

Theoretical Approaches ◽

Free Vibration of Thin-Walled Composite Shell Structures Reinforced with Uniform and Linear Carbon Nanotubes: Effect of the Elastic Foundation and Nonlinearity

Nanomaterials ◽

10.3390/nano11082090 ◽

2021 ◽

Vol 11 (8) ◽

pp. 2090

Author(s):

Avey Mahmure ◽

Francesco Tornabene ◽

Rossana Dimitri ◽

Nuri Kuruoglu

Keyword(s):

Carbon Nanotubes ◽

Free Vibration ◽

Elastic Foundation ◽

Composite Shell ◽

Free Vibrations ◽

Shell Structures ◽

Pasternak Foundation ◽

Thin Walled ◽

Basic Equations ◽

Benchmark Solutions

In this work, we discuss the free vibration behavior of thin-walled composite shell structures reinforced with carbon nanotubes (CNTs) in a nonlinear setting and resting on a Winkler–Pasternak Foundation (WPF). The theoretical model and the differential equations associated with the problem account for different distributions of CNTs (with uniform or nonuniform linear patterns), together with the presence of an elastic foundation, and von-Karman type nonlinearities. The basic equations of the problem are solved by using the Galerkin and Grigolyuk methods, in order to determine the frequencies associated with linear and nonlinear free vibrations. The reliability of the proposed methodology is verified against further predictions from the literature. Then, we examine the model for the sensitivity of the vibration response to different input parameters, such as the mechanical properties of the soil, or the nonlinearities and distributions of the reinforcing CNT phase, as useful for design purposes and benchmark solutions for more complicated computational studies on the topic.