Elastomeric mechanical metamaterials have revealed striking ability to attenuate shock loads at the macroscopic level. Reports suggest that this capability is associated with the reversible elastic buckling of internal beam constituents observed in quasistatic characterizations. Yet, the presence of buckling members induces non-affine response at the microscale, so that clear understanding of the exact energy dissipation mechanisms remains clouded. In this report, the authors examine a mechanical metamaterial that exhibits both micro-and macroscopic deformations under impact loads and devise an experimental method to visualize the resulting energy dissipation mechanisms. By illuminating the dynamic distribution of strain in the metamaterial, the authors uncover a rational way to program the macroscopic deformation and enhance impact mitigation properties. The results emphasize that mechanical metamaterials clearly integrate materials science and structural engineering, encouraging future interdisciplinary studies to capitalize on the opportunities.The blow of an impact can rapidly harm people and engineered systems. [1,2] This challenge has fueled development of resilient engineered material systems able to suppress the transmission of impact energy to the shielded body or structure. Recent attention has turned to buckling-based material system concepts, whereby elastic and/or plastic buckling structural members on a microscale level [3][4][5][6][7] are harnessed to absorb shock at the system level. Preferring the reusability of elastic buckling phenomena and the practicality of elastomers, classes of elastomeric mechanical metamaterials have been devised with internal cellular geometries that absorb elastic energy via reversible buckling events in periodic, microscale elastomeric beam constituents. [8][9][10][11][12] Under low frequency cycling of applied strain or stress, these new generations of cellular materials [13] are shown to exhibit exceptional elastic energy dissipation properties [14][15][16] due to a "reversible plasticity" effect [17] that has an analogy to energy management in cytoskeletal actin networks. [18][19][20][21] Yet, a common vision for elastomeric mechanical metamaterials is to mitigate impact, in which case high strain rates are induced. In this light, experimental evidence suggests these metamaterials are effective to dissipate sudden accelerations [9] and shocks, [11] although the exact energy mitigation mechanisms are unknown. While there are inherent ties between shock absorption mechanisms and the elastic buckling of the beam constituents in such elastomeric metamaterials, [22] when composed into material systems the presence of buckling members gives rise to non-affine response at the microscale that ultimately governs macroscopic energy dissipation properties of the system. [23,24] These internal instabilities break the direct proportionality between micro-and macroscale behaviors. [25] Although high-speed video has shed light on energy transfer and dissipation in similar problem...

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For many first-year engineering students, what it means to be an engineer is an abstract concept. Introducing major-related classes early in an engineer's education helps students answer, "what is an engineer?" However, these classes often lack connections between engineering and society. Additionally, current courses do not always effectively support students in becoming experienced problem solvers. To address the connection between engineering and society and to help students develop their confidence in problem solving, the Toy Adaptation Program (TAP) at The Ohio State University provides students with a hands-on experience modifying electronic toys for children with special needs. These adapted toys are donated to toy-lending libraries and families in-need, so that families are not burdened with the increased cost and inconvenience of purchasing marked-up adapted toys from select toy manufacturers. For this "In Progress" paper for the Community Engagement in Engineering Education Division, we will introduce the program in its current format along with our assessment techniques and next steps.

Effective suppression of impulsive elastic waves requires the reduction of the transmitted shock pulse and the elongation of shock duration. Recent experimental studies with engineered, lightweight elastomeric materials suggest that these requirements are met to large extent. The materials capitalize upon the mesoscale geometry that is known to collapse in unique ways according to the internal geometric design and magnitude of the impact force. Yet, the relations among material design, collapse trend, and resulting shock mitigation remain unknown. This research seeks to shed light on the connections using digital image correlation techniques that uncover exact origins of energy distribution through mapping of local strain fields. With a sequence of controlled shock experiments, we first identify how the impact force magnitude governs the classification of shock mitigation capability of the materials. Then, the relative variations of such trends as tailored by the internal material geometry are examined. All together, the results illuminate the range of working conditions and material designs for which shock attenuation capability of the materials remains exceptional.