I am a SNSF postdoctoral researcher in Bertoldi group at Harvard School of Engineering and Applied Sciences. I am working in the general area of mechanics of materials with a focus on designer matter to create new architected materials with novel functionalities. In my research, I get inspirations from natural and biological systems, origamikirigami and architecture.

Full text of articles are available upon request.

Recent Publications

Durable Bistable Auxetics Made of Rigid Solids
X. Shang, L. Liu, A. Rafsanjani, and D. Pasini. In Press. “Durable Bistable Auxetics Made of Rigid Solids.” Journal of Materials Research, Focus Issue: Architected Materials.Abstract
Bistable Auxetic Metamaterials (BAMs) are a class of monolithic perforated periodic structures with negative Poisson’s ratio. Under tension, a BAM can expand and reach a second state of equilibrium through a globally large shape transformation that is ensured by the flexibility of its elastomeric base material. However, if made from a rigid polymer, or metal, BAM ceases to function due to the inevitable rupture of its ligaments. The goal of this work is to extend the unique functionality of the original kirigami architecture of BAM to a rigid solid base material. We use experiments and numerical simulations to assess performance, bistability and durability of rigid BAMs at 10,000 cycles. Geometric maps are presented to elucidate the role of the main descriptors of BAM architecture. The proposed design enables the realization of BAM from a large palette of materials, including elastic-perfectly plastic materials and potentially brittle materials.
On the design of porous structures with enhanced fatigue life
F. Javid, J. Liu, A. Rafsanjani, M. Schaenzer, M. Q. Pham, D. Backman, S. Yandt, M. C. Innes, C. Booth-Morrison, M. Gerendas, T. Scarinci, A. Shanian, and K. Bertoldi. 10/2017. “On the design of porous structures with enhanced fatigue life.” Extreme Mechanics Letters, 16, Pp. 13-17. Publisher's VersionAbstract
Many components of gas turbines, including the combustion liners, ducts, casings and sealing structures, comprise metallic sheets perforated with arrays of circular cooling holes. These parts are highly prone to fatigue failure due to the stresses induced by temperature variations during operation. Here, we demonstrate both experimentally and numerically that the fatigue life of these porous components can be greatly enhanced by carefully designing the pores’ shape. In particular, we show that while the fatigue life of a metallic sheet with a square array of conventional circular cooling holes is <100k cycles, by replacing the pores with novel orthogonal S-shaped holes the life of the structure increases up to more than one million cycles. This is because the S-shaped pores introduce a soft mode of deformation based on rotation of the domains between neighboring holes that significantly affect the stress distribution and crack propagation in the structure.
Buckling-Induced Kirigami
A. Rafsanjani and K. Bertoldi. 2/24/2017. “Buckling-Induced Kirigami.” Physical Review Letters, 118, Pp. 084301. Publisher's VersionAbstract

We investigate the mechanical response of thin sheets perforated with a square array of mutually orthogonal cuts, which leaves a network of squares connected by small ligaments. Our combined analytical, experimental and numerical results indicate that under uniaxial tension the ligaments buckle out-of-plane, inducing the formation of 3D patterns whose morphology is controlled by the load direction. We also find that by largely stretching the buckled perforated sheets, plastic strains develop in the ligaments. This gives rise to the formation of kirigami sheets comprising periodic distribution of cuts and permanent folds. As such, the proposed buckling-induced pop-up strategy points to a simple route for manufacturing complex morphable structures out of flat perforated sheets.

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