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This paper presents a comparative study on the size optimization of four mesostructures to meet the design requirements for a nonpneumatic tire's (NPT) shear beam with 10% shear flexure (SF) at 10 MPa effective shear modulus. The need for such comparison is motivated from the previous research wherein a systematic design method is proposed to design a mesostructure with high SF by studying the strain energy distribution pattern in honeycomb, auxetic, and sinusoidal auxetic mesostructure. Based upon the distribution pattern, a new type of mesostructure termed S-type is invented. Although it exhibited higher SF than the other mesostructures for a comparable set of geometry, it is not possible to validate the design method without exploring the complete design space of both existing and newly invented mesostructures. In order to address this limitation, these four mesostructures are optimized using the following optimization algorithms: (i) particle swarm; (ii) genetic algorithm (GA); and (iii) FAST–SIMPLEX (using response surface method). The results show the S-type mesostructure can be configured to meet the design requirements, thereby validating the design method presented in previous research. Additionally, it is also observed that auxetic mesostructure is only 5% less than the required design target, which presents an opportunity in future, to develop an alternate design method to maximize SF other than the one that is being validated in this paper.

The evolution of meso-structures in the development of the shear band of Michelin’s non-pneumatic tire, the Tweel, is presented in this paper. Designers and researchers at Clemson University worked on a research projects with Michelin to support NIST efforts in fuel efficiency improvement and NASA efforts in manned exploration systems. The goal of each was to replace the elastomeric material of shear band with materials which can tolerate harsh temperatures and shear loads or to replace the materials with linear elastic low-hysteretic loss materials. The concepts initially proposed by ideation method were prototyped for physical testing. A case study examining the documentation reports for each project is conducted to provide a reflective understanding of how the evolution in the projects occurred. The goal of developing this retrospective is to try to identify guidelines and approaches that could be integrated into a designer driven systematic approach for custom design of meso-structures.

Much research has been conducted on effective elastic properties of meso-scaled periodic cellular material (MPCM) structures; however, limited research is found in the literature for design guidelines to develop a unit cell (UC) topology and shape for multiple loading conditions. The current methods to design topology of unit cells has experienced limitations including numerical modeling challenges and trial-and-error associated with topology optimization and intuitive methods, respectively. To address this limitation this paper aims to develop guidelines for redesign of unit cell topology and shape under in-plane shear loading. The guidelines are intended to use design knowledge for helping engineers by providing recommendations at any stage of the design process. In this paper, the guidelines are developed by changing topology characteristics to achieve a desired effective property of a MPCM structure. The effect of individual members such as side connection and transverse connection of MPCM structure when subjected to in-plane shear loading are investigated through conducting a set of numerical simulation on UCs with similar topology and shape characteristics. Based on the simulation results, the unit cell design guidelines are developed to provide recommendations to engineers on improving shear flexure of MPCM during the design process.

Over the past decade, there has been an increase in the intentional design of meso-structured materials that are optimized to target desired material properties. This paper reviews and critically compares common numerical methodologies and optimization techniques used to design these meso-structures by analyzing the methods themselves and published applications and results. Most of the reviewed research targets mechanical material properties, including effective stiffness and crushing energy absorption. The numerical methodologies reviewed include topology and size/shape optimization methods such as homogenization, Solid Isotropic Material with Penalization, and level sets. The optimization techniques reviewed include genetic algorithms (GAs), particle swarm optimization (PSO), gradient based, and exhaustive search methods. The research reviewed shows notable patterns. The literature reveals a push to apply topology optimization in an ever-growing number of 3-dimensional applications. Additionally, researchers are beginning to apply topology optimization and size/shape optimization to multiphysics problems. The research also shows notable gaps. Although PSOs are comparable evolutionary algorithms to GAs, the use of GAs dominates over PSOs. These patterns and gaps, along with others, are discussed in terms of possible future research in the design of meso-structured materials.