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Phanisri Pradeep Pratapa
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Phanisri Pradeep Pratapa
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Phanisri Pradeep Pratapa
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Pratapa, Phanisri P.
Pratapa, Phanisri Pradeep
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5 results
Now showing 1 - 5 of 5
- PublicationTriclinic Metamaterials by Tristable Origami with Reprogrammable Frustration(01-10-2022)
;Liu, Ke; ;Misseroni, Diego ;Tachi, TomohiroPaulino, Glaucio H.Geometrical-frustration-induced anisotropy and inhomogeneity are explored to achieve unique properties of metamaterials that set them apart from conventional materials. According to Neumann's principle, to achieve anisotropic responses, the material unit cell should possess less symmetry. Based on such guidelines, a triclinic metamaterial system of minimal symmetry is presented, which originates from a Trimorph origami pattern with a simple and insightful geometry: a basic unit cell with four tilted panels and four corresponding creases. The intrinsic geometry of the Trimorph origami, with its changing tilting angles, dictates a folding motion that varies the primitive vectors of the unit cell, couples the shear and normal strains of its extrinsic bulk, and leads to an unusual Poisson effect. Such an effect, associated with reversible auxeticity in the changing triclinic frame, is observed experimentally, and predicted theoretically by elegant mathematical formulae. The nonlinearities of the folding motions allow the unit cell to display three robust stable states, connected through snapping instabilities. When the tristable unit cells are tessellated, phenomena that resemble linear and point defects emerge as a result of geometric frustration. The frustration is reprogrammable into distinct stable and inhomogeneous states by arbitrarily selecting the location of a single or multiple point defects. The Trimorph origami demonstrates the possibility of creating origami metamaterials with symmetries that are hitherto nonexistent, leading to triclinic metamaterials with tunable anisotropy for potential applications such as wave propagation control and compliant microrobots. - PublicationUnraveling tensegrity tessellations for metamaterials with tunable stiffness and bandgaps(01-10-2019)
;Liu, Ke ;Zegard, Tomás; Paulino, Glaucio H.Tensegrity structures resemble biological tissues: A structural system that holds an internal balance of prestress. Owing to the presence of prestress, biological tissues can dramatically change their properties, making tensegrity a promising platform for tunable and functional metamaterials. However, tensegrity metamaterials require harmony between form and force in an infinitely–periodic scale, which makes the design of such systems challenging. In order to explore the full potential of tensegrity metamaterials, a systematic design approach is required. In this work, we propose an automated design framework that provides access to unlimited tensegrity metamaterial designs. The framework generates tensegrity metamaterials by tessellating blocks with designated geometries that are aware of the system periodicity. In particular, our formulation allows creation of Class-1 (i.e., floating struts) tensegrity metamaterials. We show that tensegrity metamaterials offer tunable effective elastic moduli, Poisson's ratio, and phononic bandgaps by properly changing their prestress levels, which provide a new dimension of programmability beyond geometry. - PublicationReprogrammable Kinematic Branches in Tessellated Origami Structures(01-06-2021)
; ;Liu, Ke ;Vasudevan, Siva P.Paulino, Glaucio H.We analyze the folding kinematics of a recently proposed origami-based tessellated structure called the Morph pattern, using thin, rigid panel assumptions. We discuss the geometry of the Morph unit cell that can exist in two characteristic modes differing in the mountain/valley assignment of a degree-four vertex and explain how a single tessellation of the Morph structure can undergo morphing through rigid origami kinematics resulting in multiple hybrid states. We describe the kinematics of the tessellated Morph pattern through multiple branches, each path leading to different sets of hybrid states. We study the kinematics of the tessellated structure through local and global Poisson's ratios and derive an analytical condition for which the global ratio switches between negative and positive values. We show that the interplay between the local and global kinematics results in folding deformations in which the hybrid states are either locked in their current modes or are transformable to other modes of the kinematic branches, leading to a reprogrammable morphing behavior of the system. Finally, using a bar-and-hinge model-based numerical framework, we simulate the nonlinear folding behavior of the hybrid systems and verify the deformation characteristics that are predicted analytically. - PublicationExperimental realization of tunable Poisson's ratio in deployable origami metamaterials(01-05-2022)
;Misseroni, Diego; ;Liu, KePaulino, Glaucio H.Origami metamaterials are known to display highly tunable Poisson's ratio depending on their folded state. Most studies on the Poisson effects in deployable origami tessellations are restricted to theory and simulation. Experimental realization of the desired Poisson effects in origami metamaterials requires special attention to the boundary conditions to enable nonlinear deformations that give rise to tunability. In this work, we present a novel experimental setup suitable to study the Poisson effects in 2D origami tessellations that undergo simultaneous deformations in both the applied and transverse directions. The setup comprises a gripping mechanism, which we call a Saint-Venant fixture, to eliminate Saint-Venant end effects during uniaxial testing. Using this setup, we conduct Poisson's ratio measurements of the Morph origami pattern whose configuration space combines features of the Miura-ori and Eggbox parent patterns. We experimentally observe the Poisson's ratio sign switching capability of the Morph pattern, along with its ability to display either completely positive or negative values of Poisson's ratio by virtue of topological transformations. To demonstrate the versatility of the novel setup we also perform experiments on the standard Miura-ori and the standard Eggbox patterns. Our results demonstrate the agreement between the theory, the simulations, and the experiments on the Poisson's ratio measurement and its tunability in origami metamaterials. The proposed experimental technique can be adopted for investigating other tunable properties of origami metamaterials in static and in dynamic regimes, such as elastic thermal expansion, and wave propagation control. - PublicationKinematics of the morph origami pattern and its hybrid states(01-01-2020)
; ;Liu, KePaulino, Glaucio H.A new degree-four vertex origami, called the Morph pattern, has been recently proposed by the authors (Pratapa, Liu, Paulino, Phy. Rev. Lett. 2019), which exhibits interesting properties such as extreme tunability of Poisson's ratio from negative infinity to positive infinity, and an ability to transform into hybrid states through rigid origami kinematics. We look at the geometry of the Morph unit cell that can exist in two characteristic modes differing in the mountain/valley assignment of the degree-four vertex and then assemble the unit cells to form complex tessellations that are inter-transformable and exhibit contrasting properties. We present alternative and detailed descriptions to (i) understand how the Morph pattern can smoothly transform across all its configuration states, (ii) characterize the configuration space of the Morph pattern with distinguishing paths for different sets of hybrid states, and (Hi) derive the condition for Poisson's ratio switching and explain the mode-locking phenomenon in the Morph pattern when subjected to in-plane deformation as a result of the inter-play between local and global kinematics.