Presentation on theme: "Environmental chamber manufactured by Lunaire Environmental (Model number: CEO910W-4 A B IV. Procedures Two samples were formed for both ballistic materials."— Presentation transcript:
Environmental chamber manufactured by Lunaire Environmental (Model number: CEO910W-4 A B IV. Procedures Two samples were formed for both ballistic materials. For Unidirectional Dyneema, the samples were constructed from 15 12x12 layers each, while for Kevlar KM2, 32 12x12 layers were used. The samples for both materials were left to rest in lab environmental conditions for approximately 14 hours. Then all samples were vacuum sealed. For each of the ballistic materials, one sample was sealed at maximum vacuum and the other at 15 inches of mercury (IOM). Afterwards the samples were placed inside the environmental chamber for 4 hours acclimatization period prior to the Rct testing. The settings on the hotplate and the environmental chamber were according to the ISO 11092 standard. However, the acclimatization procedure had been altered as was described previously. The same procedure was repeated for four consecutive days. Investigating the need for acclimatization before measuring dry thermal resistance of vacuum sealed materials Panagiotis Kamenidis, Donna Branson, Semra Peksoz, Huantian Cao Insti Department of Design Housing and Merchandizing Oklahoma State University, Stillwater, OK Introduction: According to the ISO (11092) standard for measuring dry thermal resistance (Rct) of textile materials with a guarded hotplate, samples 5 mm thick or more should be acclimatized for at least 24 hours prior to testing. There was no reference found to indicate an acclimatization methodology prior to testing the Rct of thick vacuum sealed samples. The primary goal of this study was to determine the influence of lab environmental conditions on Rct values of textile fabric samples prior to vacuum sealing. The secondary objective was to define differences by level of vacuum sealing on the two types of ballistic materials that were tested. Materials and Methods: I. Ballistic materials Two types of commercially available ballistic fabrics were selected. KM2 Kevlar (woven, composed of aramid fibers) A Unidirectional Dyneema (non-woven, composed of polyethylene fibers) B II. Vacuum sealing pouches One commercially available type of vacuum sealing pouch (3mm thick) was used. It was composed of nylon/polyethylene and manufactured by Pleasant Hill Grain. III. Instruments Table-top vacuum sealer manufactured by Multivac (Model number: A300/16MC series 1994) Sweating guarded hotplate manufactured by Measurement Technology (Model number: SGHP-8.2) housed inside an environmental chamber Results: A summary of the recorded Rct and environmental measurements is presented in Table 1. The humidity during the four days of the experiment ranged between 50% and 75% while the temperature was between 67 and 73 o F. Conclusion : Ambient environmental conditions during storage of Kevlar KM2 and Unidirectional Dyneema samples prior to vacuum sealing and subsequent thermal testing, did not affect the Rct measurements of the samples. Thus there is no need to acclimatize these two ballistic materials 24 hours as indicated by the ISO 11092 standard. Furthermore, the effect of vacuum sealing on Rct suggest that there is a possibility to control the thermal resistance of ballistic materials by vacuum sealing them at different levels. This phenomenon is currently under investigation from the same team of researchers that worked for this study. A. Environmental conditions Among different environmental conditions, there was no significant difference on Rct measurements for both ballistic materials (Table 2). B. Vacuum level Among different vacuum levels, there was a significant difference on Rct measurements for both ballistic materials (Table 2). Both Kevlar KM2 (Table 3) and Unidirectional Dyneema (Table 4) presented lower Rct values when maximum vacuum occurred. Institute for Protective Apparel Research and Technology Acknowledgements: William MacGlyn, PhD Fig 1. A&B ballistic materials Fig 2. A Hotplate, B Environmental chamber Table 1. Rct values and environmental conditions during testing. Kevlar RctDyneema RctEnvironmental conditions Vacuum level (IOM) Maximum (0.2) 15 Maximum (0.08) 15Humidity (%)Temperature ( o F) Day 10.1280.17860.02760.11927473 Day 20.11960.18920.05640.09936467 Day 30.11850.18240.03540.10845067 Day 40.10920.17940.02620.0977567 Table 2. ANOVA analysis of both ballistic materials Ballistic material SourceDFMean squareF valuePr > F KevlarVacuum level10.00808356195.060.001 Different days 30.000040960.990.504 DyneemaVacuum level10.0096813648.010.006 Different days 30.000094470.470.725 Table 3. Vacuum level effect on Rct of Kevlar KM2 Vacuum Level (IOM)Rct ( o C m 2 / Watts) 0.2 0.1188 b z 150.1824 a z Means with different letters within columns are significantly different by LSD test at 0.05 level Table 4. Vacuum level effect on Rct of Unidirectional Dyneema Vacuum Level (IOM)Rct (oC m2/ Watts) 0.08 0.0364 b z 150.1060 a z Means with different letters within columns are significantly different by LSD test at 0.05 level Funding:
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