Multifunctional structural batteries and supercapacitors have the potential to improve performance and efficiency in advanced lightweight systems. A critical requirement is a structural electrolyte with superior multifunctional performance. We present here structural electrolytes prepared by the integration of liquid electrolytes with structural epoxy networks. Two distinct approaches were investigated: direct blending of an epoxy resin with a poly(ethylene-glycol) (PEG)-or propylene carbonate (PC)-based liquid electrolyte followed by in-situ cure of the resin; and formation of a porous neat epoxy sample followed by backfill with a PC-based electrolyte. The results show that in situ cure of the electrolytes within the epoxy network does not lead to good multifunctional performance due to a combination of plasticization of the structural network and limited percolation of the liquid network. In contrast, addition of a liquid electrolyte to a porous monolith results in both good stiffness and high ionic conductivity that approach multifunctional goals.
Underbody Blast (UBB) events subject vehicle occupants to large accelerations that often result in severe lumbar spine injury. Little knowledge exists on the intervertebral disc response during high-rate vertical accelerative loading. To address this gap, the current study investigates intradiscal pressures under UBB loading utilizing biomechanical testing from: 1) isolated Post Mortem Human Surrogate (PMHS) lumbar spine motion segments (LMS) in a custom-designed drop tower fixture; and 2) whole body (WHBO) PMHS in a custom-designed Vertically Accelerated Load Transfer System. During testing, intradiscal pressures were comparable between the LMS and WHBO tests, with non-fracture cases producing higher average peak pressures than fractured tests. Additionally, WHBO testing demonstrated that upper body posture can influence lumbar pressure responses. The current study evaluates lumbar intradiscal pressure transduction as it relates to vertebral fracture in both component and whole body experiments.
In applications where a combination of good strength and corrosion resistance is required, 17 − 4 precipitation hardenable (PH) stainless steel is a common material choice. This alloy is traditionally processed through a combination of casting, rolling, and machining. A variety of heat treatments are used to anneal and harden the material via precipitation strengthening. While additive manufacturing (AM) removes many geometric design constraints from these traditional forming processes, until recently, structures fabricated via laser powder bed fusion (L-PBF) were porous and contained undesirable columnar grain structures that contributed to unpredictable and anisotropic mechanical properties. However, recent advances in L-PBF processing technology including improved gas ow, powder atomization, and print parameter optimization enable printing of high-quality AM 17 − 4 PH with properties that are comparable to traditionally processed material. With the ultimate goal of establishing mechanical property baselines involving numerous L-PBF processes, six vendors (including this work) fabricated tensile and fatigue samples of 17 − 4 using a variety of machines. Ultimately, after standard solution annealing and heat treating, the microstructure and mechanical properties across vendors converged with very few, easily explainable exceptions. In particular, powder atomized in nitrogen promoted formation of retained austenite that lead to a yield point phenomenon in as-built conditions and high surface roughness from as-built surfaces reduced the fatigue strength. However, with conventional post-processing heat treatments and surface polishing, AM 17 − 4 PH behaved comparably and consistently to conventionally processed material.
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