Prof. Ivan Petrović, PhD, M. Arch (1932–2000)

Svetel, Igor

doi:10.1016/s0926-5805(01)00081-4

Cited by 3 publications

(3 citation statements)

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“…His primary objective was to be able to use these structures for buildings or architecture devices. Petrovic was also the first person to use the term "Vacuumatics" (Svetel (2002)). This definition describes the integration of granular jamming into a deformable structure and control by vacuum.…”

Section: Granular Jamming and Vacuumaticsmentioning

confidence: 99%

Switchable stiffness morphing aerostructures based on granular jamming

Brigido-González¹,

Burrow

Woods

2019

Journal of Intelligent Material Systems and Structures

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One of the persistent challenges facing the development of morphing aerostructures is the need to have material and structural solutions which provide a compromise between the competing design drivers of low actuation energy and high stiffness under external loads. This work proposes a solution to this challenge in the form of a novel switchable stiffness structural concept based on the principle of granular jamming. In this article, the concept of using granular jamming for controlling stiffness is first introduced. Four-point bending tests are used to obtain the flexural rigidity and bending stiffness of three different granular materials under different levels of applied vacuum loading. Nonlinear finite element analysis simulations using experimentally derived nonlinear material properties show good agreement with experiment. A specific application of this concept is then proposed based on the Fish Bone Active Camber morphing airfoil. A unit cell of this concept is built, tested and analysed, followed by the first prototype of a complete switchable stiffness Fish Bone Active Camber morphing airfoil, which is experimentally shown to be able to achieve an increase in stiffness of up to 300% due to granular jamming.

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Section: Granular Jamming and Vacuumaticsmentioning

confidence: 99%

Switchable stiffness morphing aerostructures based on granular jamming

Brigido-González¹,

Burrow

Woods

2019

Journal of Intelligent Material Systems and Structures

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“…Such devices have been used to create architectural, robotic, and civil engineering structures, but to date have not been applied to morphing aircraft concepts. One early example of a granular jamming bases structure was the dome structure presented in [20], which was built of Expanded Polystyrene beads within a polymer membrane. The main objective of this work was to demonstrate a concept for reconfigurable buildings.…”

Section: B Granular Jammingmentioning

confidence: 99%

An analytical model for granular jamming beams with applications in morphing aerostructures

Brigido

Burrow

Woods

2020

AIAA Scitech 2020 Forum

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Modern aircraft wings use discrete, flapped control surfaces that are simple and effective, but which create a significant drag and noise penalty when used. This research is working towards the replacement of these flaps with a continuous morphing device that can increase the aerodynamic performance and reduce noise emissions. However, the need to create smoothly morphing aerostructures presents a fundamental challenge in that the structures need to be stiff enough to resist aerodynamic and inertial loads while being flexible enough to change shape with minimal energy required. One way to address this competing set of constraints would be to use a material that is able to actively vary its stiffness. Such a device could be softened while morphing and then stiffened to hold its morphed shape. In this work, granular jamming is proposed as a mechanism for creating a material which can change stiffness from a liquid-like state to a solid-like state through the application of an applied pressure field which jams together the grains to stiffen an otherwise soft material. The basic concept of switchable stiffness for morphing aircraft has been shown in previous work. This paper introduces an analytical model to describe the bending dominated behaviour of granular jamming based morphing structures. Four-point bending experiments are performed to validate the model, and detailed strain fields from digital image correlation measurements are used to further elucidate the micro-mechanics. The experimental data was compared against predictions from the proposed model, where it was seen that while the model is able to capture the presence of different regimes of response, the overall stiffness and strength are overpredicted. Possible sources of discrepancy are highlighted and motivate future work.

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“…In recent years, granular-jamming structures have been used to build various concepts of smart structures to vary their stiffness depending on operating conditions. One smart structure that used vacuum-packed particles was Petrovic's smart dome [4]. The dome has polystyrene beads inside a polymer membrane and can be reshaped into different geometries.…”

Section: Introductionmentioning

confidence: 99%

Flexural Models for Vacuum-Packed Particles as a Variable-Stiffness Mechanism in Smart Structures

et al. 2022

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Vacuum-packed particle (VPP) systems have been recently used in the development of smart structures due to their ability to actively change material stiffness through the mechanism of granular jamming. By altering the strength of the vacuum pressure applied to the particles, the material can be proportionally and reversibly transitioned from a liquidlike low-stiffness state to a stiff state. The ability to control material stiffness in this way opens up different possibilities for the design of morphing and smart structures by allowing them to soften during deformation to reduce actuation energy requirements and to then stiffen once the desired shape has been achieved to provide a zero-energy holding mechanism. The following research describes two useful models that predict the mechanical response of VPP beams under flexural loading. Firstly, four-point bending tests with digital image correlation strain mapping are performed in order to measure the axial and transverse strains in a bending beam made from vacuum-packed particles. The test results show a nonlinear mechanical response, including a change in beam thickness with deformation, that motivated an analytical model of the structure incorporating a nonlinear material stress model based on the Mohr-Coulomb failure envelope. In addition, finite-element simulations are implemented using a Johnson-Cook model extension to predict the response under loading of three-dimensional beam elements at different vacuum pressure levels. Lastly, the models are compared to the experimental results, indicating good agreement. Both methods are shown to be useful for predicting the variation of stiffness of vacuum-packed particle beams.

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Prof. Ivan Petrović, PhD, M. Arch (1932–2000)

Cited by 3 publications

References 0 publications

Switchable stiffness morphing aerostructures based on granular jamming

Switchable stiffness morphing aerostructures based on granular jamming

An analytical model for granular jamming beams with applications in morphing aerostructures

Flexural Models for Vacuum-Packed Particles as a Variable-Stiffness Mechanism in Smart Structures

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