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Despite plenty of static and dynamic mechanical measurements and modeling for bulk polydimethylsiloxane (PDMS) specimens, a notable gap exists in comprehensively understanding the dynamic mechanics under large cycle, low strain conditions, especially for microscale samples. This study integrates tensile testing and nanoindentation techniques to compare dynamic mechanical response for bulk PDMS samples and μ-pillars. The results from cyclic tensile testing, which involved up to 10,000 cycles at a strain range of 10%–20%, indicate a stabilization of energy dissipation rate after the initial 25 cycles. This attributes to stress relaxation and strain hardening, validating by rapid dual-phase exponential decay in maximum stress, coupled with an incremental increase in elastic modulus. In comparison to tensile testing, μ-pillars exhibited a 0.82% reduction in stiffness, stabilizing ~600th cycle. Concurrently, there was an approximately twofold increase in approaching distance during the initial 120 cycles, and an approximately fourfold increase in dissipated energy over the first 80 cycles, before reaching a plateau. This lagging hysteresis effect attributes to the distribution of the resultant force, including top tension, bottom compression, and base tilt. Overall, this study illuminates temporal mechanical deformations in PDMS under two application scenarios, enhancing our understanding of PDMS mechanical behavior. [ABSTRACT FROM AUTHOR]

Boron Nitride Nanotubes (BNNTs), a 1D nanomaterial with extraordinary mechanical properties, are structurally like carbon nanotubes. BNNTs possess superior thermal stability of ∼900 °C, higher resistance to oxidation at elevated temperatures, and enhanced neutron shielding capacity. These benefits open a wider processing window for manufacturing BNNT-reinforced metal matrix composites (MMC) and hold promise for several structural applications, including radiation shielding. This critique presents the current status, challenges, and future scientific possibilities of BNNT-reinforced MMC. Particular emphasis is laid on the progress made in this area regarding the synthesis, manufacturing, and characterization of BNNT-MMCs to date. The challenges associated with various processing techniques, including additive manufacturing (AM), are discussed in the fabrication of BNNT-MMCs. The experimental mechanics and structure-property relationship modeling are examined in detail to establish the utilization of BNNT-reinforced MMCs. Additionally, prospective research areas with a huge untapped potential for BNNT-MMCs are suggested. The scientific framework behind these methods' chronological development is analyzed, and a pathway for subsequent advancement is projected. By providing a comprehensive overview, this critique aims to facilitate further progress in BNNT-reinforced MMCs. [ABSTRACT FROM AUTHOR]

High‐resolution printing afforded by two‐photon polymerization (2PP) has opened up vast design space, spanning over four orders of magnitude (sub‐μm to cm), unleashing the opportunity to fabricate architected materials with intriguing mechanical characteristics. This study seeks to exploit direct laser writing to print accordion‐shaped honeycomb lattices constituted of slender micro‐membranes to achieve in‐plane mechanical anisotropy. The deformation mechanisms governing orientation‐sensitive mechanical properties of the lattice are examined by in situ investigations in a scanning electron microscope. The microlattice displays greater flexibility, compliance, and strain hardening during in‐plane compression, whereas it is highly stiff and resistant to fatigue in the out‐of‐plane orientation. The high aspect ratio of accordion‐shaped cells imparts prominent in‐plane anisotropy, with longitudinal stiffness twice the transverse stiffness. Folding, interlocking, and compaction of micro‐walls are the major deformation mechanisms, inducing brilliant energy dissipation ability, with up to 87% mechanical work‐absorption. Digital image correlation analysis reveals that strain re‐distribution facilitated by hinges dictates the recoverability of the microlattice. This work provides useful mechanistic insights at the micrometer length scale for tuning the orientation‐sensitive mechanical response of mesostructures printed by 2PP. [ABSTRACT FROM AUTHOR]