Three different types of yarn have been subjected to transverse impact experiments in efforts to gain an understanding of local yarn failure and to provide input parameters for future transverse yarn impact simulations. Dupont™ Kevlar® KM2, DSM Dyneema® SK76, and AuTx® from JSC Kamenskvolokno were selected as representative materials, as the former two are commonly implemented into bullet resistant panels and the latter is a promising material for future impact resistant fabrics. In order to assess the effect of projectile nose shape on the critical rupture velocity range for each yarn type, three missile geometries have been implemented, namely a 0.30 caliber rounded head, a 0.30 caliber chisel nosed fragment simulation projectile (FSP), and a high-carbon steel razor blade. As opposed to one single velocity wherein yarn behavior transitions from transverse wave development to immediate local failure, a range is defined wherein progressive filament failure is detected with increasing impact velocities. Such ranges are determined for all yarn types using the three projectile geometries yielding critical velocity transition regions of increasing value when impacting via razor blade, FSP, and round projectile heads, accordingly. In addition, post-mortem fracture surfaces recovered from impact experiments have been imaged so as to elucidate the mechanism of failure throughout the range of velocities tested for each projectile type and yarn material and said fracture surfaces correlate well with impact velocity and projectile nose geometry.
In current electric vehicles batteries fulfill only the role of power source and are stored within the passenger cabin, protected from external impact loads. This study considers a multifunctional, damage tolerant battery system which combines the energetic material with mechanically sacrificing elements that control mechanical stresses and dissipate energy. With such a multifunctional battery system in place it is proposed to place the battery pack into the secondary safe zone of a unibody-type vehicle. Full-vehicle crash analysis via finite element simulations are conducted for several battery pack configurations, thereby comparing the multifunctional battery system to battery packs with batteries alone and battery packs where cellular solids are used as energy absorbers. The analysis demonstrates the use of a multifunctional (damage tolerant and energy storage capable) battery system to ensure battery safety and aid in the energy absorption in a crash overall. The use of the multifunctional battery systems can aid in solving technology limitations of electric vehicles.
In this paper, we report on a multifunctional battery assembly, which possesses a balanced combination of energy storage capability and resistance to electrical failure under mechanical impact loading. The Granular Battery Assembly (GBA) presented here exhibits a mechanical response that emerges from features of granular and cellular media. We demonstrate that for the specific GBA embodiment considered in the present study, the electrical reliability following a mechanical loading event is substantively increased compared to that of plain battery cells. The increased reliability is due to the sacrificial material elements interspersed between the battery units, attributing energy absorption and local stress limiting.
AAE 35200 is an aerospace structural mechanics course for third-year students majoring in Aeronautical and Astronautical Engineering at Purdue University. In AAE 35200, students were given the opportunity to attend weekly optional one-hour supervised homework sessions instructed by a graduate teaching assistant (TA) during the Fall 2015 semester. The contents of the supervised homework session included the theoretical background and technical details about the assigned homework problems, knowledge beyond the original context of the problems, and alternative approaches to solve the problems. In this study, we investigated the effect of the supervised homework sessions on students' homework and exam scores. We found that the supervised homework sessions had the most influence on the homework scores of the students with low native ability. Also, as the byproduct of the study, we investigated the effect of the Scholastic Aptitude Test (SAT)-Math scores on students' academic performance. We found that the SAT-Math score was not correlated with the exam score. In order for us to rigorously study the effect of student attributes (independent variables) on the academic performance (dependent variables), we performed an analysis of covariance (ANCOVA) on the experimental data, controlling for student attributes. We found that the attendance and interaction between SATMath and attendance were the two terms that influenced the homework scores the most.
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