Extreme mechanics in laminated shells: New insights

Groh, Rainer; Pirrera, Alberto

doi:10.1016/j.eml.2018.07.004

Cited by 6 publications

(2 citation statements)

References 33 publications

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“…For instance, the analyst has very limited control over the equilibrium path that is being traced, such that unwanted path-jumping typically occurs. As a viable alternative, the in-house MATLAB-based FE code [3] has been employed as it has been validated on various occasions against commercial FE packages (as much as these allow given the lack of comparable capabilities), other results in literature, and also experimental results-the interested reader is encouraged to study these selected examples [31,32,33].…”

Section: Model Definitionmentioning

confidence: 99%

Nudging Axially Compressed Cylindrical Panels Toward Imperfection Insensitivity

Cox

Groh

Pirrera

2019

Journal of Applied Mechanics

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Curved shell structures are known for their excellent load-carrying capability and are commonly used in thin-walled constructions. Although theoretically able to withstand greater buckling loads than flat structures, shell structures are notoriously sensitive to imperfections owing to their postbuckling behavior often being governed by subcritical bifurcations. Thus, shell structures often buckle at significantly lower loads than those predicted numerically and the ensuing dynamic snap to another equilibrium can lead to permanent damage. Furthermore, the strong sensitivity to initial imperfections, as well as their stochastic nature, limits the predictive capability of current stability analyses. Our objective here is to convert the subcritical nature of the buckling event to a supercritical one, thereby improving the reliability of numerical predictions and mitigating the possibility of catastrophic failure. We explore the elastically nonlinear postbuckling response of axially compressed cylindrical panels using numerical continuation techniques. These analyses show that axially compressed panels exhibit a highly nonlinear and complex postbuckling behavior with many entangled postbuckled equilibrium curves. We unveil isolated regions of stable equilibria in otherwise unstable postbuckled regimes, which often possess greater load-carrying capacity. By modifying the initial geometry of the panel in a targeted—rather than stochastic—and imperceptible manner, the postbuckling behavior of these shells can be tailored without a significant increase in mass. These findings provide new insight into the buckling and postbuckling behavior of shell structures and opportunities for modifying and controlling their postbuckling response for enhanced efficiency and functionality.

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Section: Model Definitionmentioning

confidence: 99%

Nudging Axially Compressed Cylindrical Panels Toward Imperfection Insensitivity

Cox

Groh

Pirrera

2019

Journal of Applied Mechanics

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“…Refs. [12][13][14][15]. Through careful tailoring of structural form and the composites' anisotropic stiffness, bespoke nonlinear responses can be readily achieved.…”

Section: Introductionmentioning

confidence: 99%

Visualising Compliance of Composite Shell Mechanisms

Stacey

O’Donnell

Schenk

et al. 2020

Volume 10: 44th Mechanisms and Robotics Conference (MR)

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In the design of isotropic compliant shell-based mechanisms a desired response of an end-effector is commonly achieved through careful selection of shell geometry and material. However, for applications such as the design of medical support devices the shell must conform to a highly constrained set of permissible geometries, limiting tailorability. One solution to this design challenge is to exploit anisotropic material behaviour. Advanced composite materials may be elastically tailored by varying the fibre orientation, but at the cost of increased design complexity. Herein we present an approach for capturing the effects of material anisotropy on compliant shell mechanisms by providing the designer with a method for visualising their response in a physically intuitive manner. We extend the mechanism characterisation technique of Lip-kin and Patterson [1] using eigen-decomposition, and visualise the compliance vectors for structures with material anisotropy. We characterise the behaviour of cantilevered “tape-spring” shell geometries with varying enclosed angles using nonlinear finite element analysis. For small enclosed angles we observe significant reorienting of the compliance vectors due to stiffness anisotropy; as the enclosed angle is increased, geometry dominates the response. However, in an intermediate region both geometric and stiffness effects interact, highlighting the potential richness of the design space.

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