Post-buckling optimisation strategy of imperfection sensitive composite shells using Koiter method and Monte Carlo simulation

Liguori, Francesco S.; Madeo, Antonio; Magisano, Domenico; Leonetti, Leonardo; Garcea, Giovanni

doi:10.1016/j.compstruct.2018.03.023

Cited by 46 publications

(38 citation statements)

References 41 publications

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“…25. The modified LRSM lower-bound for cylindrical shells under pure bending is given by equation (17). The LRSM lower-bound delivers significantly higher KDFs for the buckling moment than the NASA SP-8019 if Z > 875 and vice versa.…”

Section: Comparison With Experimental Knockdown Factorsmentioning

confidence: 99%

“…Over the years different concepts to consider the influence of imperfection on the buckling load have been developed. One of these concepts is Koiter's asymptotic analysis which can be used to consider the influence of geometric imperfections for the design of slender structures [16], [17]. The most commonly used approach is based on the application of KDFs like the NASA SP guideline and Eurocode guidelines [18], [19].…”

Section: Introductionmentioning

confidence: 99%

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On the development of shell buckling knockdown factors for imperfection sensitive conical shells under pure bending

Wagner

Hühne

Khakimova³

2019

Thin-Walled Structures

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Thin-walled cylindrical shells are used as adapters between cylindrical shells of different diameters in launch-vehicle systems or as tailbooms in helicopters. A major loading scenario for cylindrical shells is bending. The buckling moment of these shells is very sensitive to imperfections (geometry, loading conditions) which results in a critical disagreement between theoretical and experimental results for axially loaded cylindrical shells. The design of these stability critical shells is based on classical buckling loads obtained by a linear analysis which are corrected by a single knockdown factor (0.41-NASA SP-8019) for all cone geometries. This practice is well established among designers and hasn't changed for the past 50 years because the buckling behavior is till today not very well understood. Within this paper a reduced stiffness analysis for cylindrical shells under pure bending is performed. Data of previous experimental testing campaigns are used to validate the new design criteria for different cylindrical shell geometry configurations. The results show that the application of the new design recommendation for cylindrical shell structures results in increased knockdown factors for the buckling moment which in turn may lead to a significant weight reduction potential. All ABAQUS-Python scripts and the results generated for this article are deposited in the Elsevier repository.

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Section: Comparison With Experimental Knockdown Factorsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On the development of shell buckling knockdown factors for imperfection sensitive conical shells under pure bending

Wagner

Hühne

Khakimova³

2019

Thin-Walled Structures

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“…With this tool, they were able to evaluate statistically the effect of the imperfection on the load capacity as well as the sensitivity to the amplitude of the worst imperfection. With a similar strategy based on stochastic simulations, Liguori et al [37], produced a tool to optimise the stacking sequence of slender composite shells detecting both the best layup and the worst shape of geometrical imperfection and its effect on the collapse load. Moreover, in their most recent work, Liguori et al [38] applied this Koiter-inspired method, coupled with Monte-Carlo and stochastic algorithm, to optimise the post-buckling behaviour of a variable angle tow (VAT) wingbox.…”

Section: Eigenvalue/eigenmode Analysismentioning

confidence: 99%

“…In all, these studies can be useful to assess the most critical set of impacted cases considering the number, relative sizes and damage implantation location on the panels with a low computational cost. It is the author's opinion that more holistic tools [36], [37], [38] could be implemented for achieving the optimum structure considering the initial imperfection. However, this is beyond the scope of this study and a simpler eigenvalue/eigenmode analysis is applied to obtain an insight on the criticality of the induced damage on the post-buckling behaviour of the examined panels.…”

Section: Eigenvalue/eigenmode Analysismentioning

confidence: 99%

Numerical FEA parametric analysis of CAI behaviour of CFRP stiffened panels

Gaitanelis

Giannopoulos

Theotokoglou

2019

Thin-Walled Structures

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This paper examined the effect of numerical modelling parameters on the accuracy and computational efficiency of Carbon Fibre Reinforced Polymer (CFRP) stiffened panels under Compression After Impact (CAI). Pristine and damaged CFRP stiffened panels were subjected to compression in Abaqus ® software using Cohesive Zone Model (CZM) method. Various case studies were examined and the effect of the stiffness parameters of the cohesive elements was critically assessed. Moreover, the required number of cohesive zones to fully capture the damage mechanisms of the impacted and pristine panels under compressive loading was examined. The results showed that a wrong set of parameters can even lead to neglecting the induced damage and can cause severe convergence problems in the numerical model. The importance of the Overall Meshing Factor (OMF) was highlighted and a user-defined subroutine (USDFLD) was applied to capture the decrease in the load bearing capability of an impacted panel prior to the compressive loading, since CZM was found insufficient for this scope. The above-mentioned remarks illustrated the process of investigating the optimum numerical parameters set to achieve an accurate and efficient finite element modelling of the stiffened panels structural performance and maximum load-carrying capability, when subjected to CAI loading.

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“…More recently, a solution algorithm based on Koiter’s theory implemented within a Finite Element environment was proposed in [ 26 , 27 ]. It allows structures to be optimized with general geometries, loading and boundary conditions.…”

Section: Introductionmentioning

confidence: 99%

Optimal Design of CNT-Nanocomposite Nonlinear Shells

et al. 2020

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Carbon nanotube/polymer nanocomposite plate- and shell-like structures will be the next generation lightweight structures in advanced applications due to the superior multifunctional properties combined with lightness. Here material optimization of carbon nanotube/polymer nanocomposite beams and shells is tackled via ad hoc nonlinear finite element schemes so as to control the loss of stability and overall nonlinear response. Three types of optimizations are considered: variable through-the-thickness volume fraction of random carbon nanotubes (CNTs) distributions, variable volume fraction of randomly oriented CNTs within the mid-surface, aligned CNTs with variable orientation with respect to the mid-surface. The collapse load, which includes both limit points and deformation thresholds, is chosen as the objective/cost function. An efficient computation of the cost function is carried out using the Koiter reduced order model obtained starting from an isogeometric solid-shell model to accurately describe the point-wise material distribution. The sensitivity to geometrical imperfections is also investigated. The optimization is carried out making use of the Global Convergent Method of Moving Asymptotes. The extensive numerical analyses show that varying the volume fraction distribution as well as the CNTs orientation can lead to significantly enhanced performances towards the loss of elastic stability making these lightweight structures more stable. The most striking result is that for curved shells, the unstable postbuckling response of the baseline material can be turned into a globally stable response maintaining the same amount of nanostructural reinforcement but simply tailoring strategically its distribution.

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Post-buckling optimisation strategy of imperfection sensitive composite shells using Koiter method and Monte Carlo simulation

Cited by 46 publications

References 41 publications

On the development of shell buckling knockdown factors for imperfection sensitive conical shells under pure bending

On the development of shell buckling knockdown factors for imperfection sensitive conical shells under pure bending

Numerical FEA parametric analysis of CAI behaviour of CFRP stiffened panels

Optimal Design of CNT-Nanocomposite Nonlinear Shells

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