ASTM INTERNATIONAL Selected Technical Papers Performance of Protective Clothing and Equipment: 10th Volume, Risk Reduction Through Research and Testing STP 1593 Editors: Brian Shiels Karen Lehtonen Selected technical PaPerS StP1593 Editors: Brian Shiels and Karen Lehtonen Performance of Protective Clothing and Equipment: 10th Volume, Risk Reduction Through Research and Testing ASTM STOCK #STP1593 DOI: 10.1520/STP1593-EB ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959 Printed in the U.S.A Library of Congress Cataloging-in-Publication Data ISBN: 978-0-8031-7631-7 ISSN: 1040-3035 Copyright © 2016 ASTM INTERNATIONAL, West Conshohocken, PA All rights reserved This material may not be reproduced or copied, in whole or in part, in any printed, mechanical, electronic, flm, or other distribution and storage media, without the written consent o f the publisher Photocopy Rights Authorization to photocopy items for internal, personal, or educational classroom use, or the internal, personal, or educational classroom use o f specifc clients, is granted by ASTM International provided that the appropriate fee is paid to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http://www.copyright.com/ The Society is not responsible, as a body, for the statements and opinions expressed in this publication ASTM International does not endorse any products represented in this publication Peer Review Policy Each paper published in this volume was evaluated by two peer reviewers and at least one editor The authors addressed all o f the reviewers’ comments to the satis faction o f both the technical editor(s) and the ASTM International Committee on Publications The quality o f the papers in this publication re f ects not only the obvious e forts o f the authors and the technical editor(s), but also the work o f the peer reviewers In keeping with long-standing publication practices, ASTM International maintains the anonymity o f the peer reviewers The ASTM International Committee on Publications acknowledges with appreciation their dedication and contribution o f time and e fort on behal f o f ASTM International Citation of Papers When citing papers from this publication, the appropriate citation includes the paper authors, “paper title,” STP title, STP number, book editor(s), ASTM International, West Conshohocken, PA, year, page range, paper doi, listed in the footnote o f the paper A citation is provided on page one o f each paper Printed in Bay Shore, NY September, 2016 Foreword THIS COMPILATION OF Selected Technical Papers, STP1593, Performance of Protective Clothing and Equipment: 10th Volume, Risk Reduction rough Research and Testing, contains peer-reviewed papers that were presented at a symposium held January 28–29, 2016, in San Antonio, Texas, USA e symposium was sponsored by ASTM International Committee F23 on Personal Protective Clothing and Equipment T T Symposium Chairpersons and STP Editors: Brian Shiels PBI Performance Products, Inc Charlotte, NC, USA Karen Lehtonen LION Dayton, OH, USA Contents Overview ix Synchronizing and Integrating Standards into Next Generation First Responder Personal Protective Equipment Development: An Implementation of the National Strategy for CBRNE Standards Assessing Design and Materials for Flame-Resistant Garments 11 Theories from Evaluation: How Arc Flash Protective Fabrics Work to Protect in the Hazard 27 A Heat Transfer Analysis and Alternative Method for Calibration of Copper Slug Calorimeters 42 An Evaluation of the E fects of Bleach Products and Fabric Softener on Properties of a Common Flame-Resistant Cotton-Nylon Fabric 63 Philip Mattson, John Merrill, Teresa Lustig, and William Deso Margaret Auerbach, Thomas God frey, Michael Grady, and Margaret Roylance Hugh Hoagland, Stacy L Klausing, and Jill A Kirby Thomas A God frey and Gary N Proulx Jill A Kirby, Stacy L Klausing, and Hugh Hoagland Parametric Study of Fabric Characteristics’ E fect on Vertical Flame Test Performance Using Numerical Modeling Esther Kim, Nicholas Dembsey, and Thomas A God frey Advanced Layering System and Design for the Increased Thermal Protection of Wildland Fire Shelters Anita Nagavalli, Alexander Hummel, Halil I Akyildiz, John Morton-Aslanis, and Roger Barker v 78 102 A Comparison of Test Methods for Evaluating Textiles for Protection from Hot Water Splash 117 E fects of Convective and Radiative Heat Sources on Thermal Response of Singleand Multiple-Layer Protective Fabrics in Benchtop Tests 131 High-Intensity Thermal Testing of Protective Fabrics with a CO Laser 159 Comparisons of Two Test Methods for Evaluating the Radiant Protective Performance of Wildland Firef ghter Protective Clothing Materials 178 Experimental Study of Heat Flux in Propane Flash Fires 195 Considerations for Applying Man-in-Simulant Test Methodologies for the Evaluation of Fully Encapsulating Chemical Protective Ensembles 212 Permeation of Active Ingredient in Pesticide Formulations Through Single-Use and Reusable Chemical-Resistant Gloves 233 Development and Validation of an Alternative Chemical Permeation Test Cell 250 Interlaboratory Variation for Permeation Test Standards and Considerations for Test Materials 272 Use of Thermal Mannequins for Evaluation of Heat Stress Imposed by Personal Protective Equipment 285 Heat Strain in Chemical Protective Coveralls—Are Thermal Sweating Mannequin Tests More Informative than Sweating Hot Plate Tests? 296 Alternative Methodologies for Determining the Impact of Clothing Ventilation in Structural Firef ghter Turnout Suits 313 Development of a Human Sensation-Relevant Method for Measuring Phase Change Materials 331 Ghulam Murtaza, Jane C Batcheller, Stephen A Paskaluk, and Mark Y Ackerman David Torvi, Moein Rezazadeh, and Christopher Besp f ug John Fitek, Margaret Auerbach, Thomas A God frey, and Michael Grady Alex Hummel, Kyle Watson, and Roger Barker Stephen A Paskaluk and Mark Y Ackerman R Bryan Ormond Anugrah Shaw, Ana Carla Coleone, and Joaquim Machado-Neto Christopher J Mekeel and Peng fei Gao William Gabler and R Bryan Ormond Xiaojiang Xu, Julio A Gonzalez, Anthony J Karis, Timothy P Rioux, and Adam W Potter ShuQin Wen, Jane Batcheller, and Stewart Petersen Meredith McQuerry, Emiel DenHartog, Roger Barker, and Alex Hummel Daniel B Howe, Keith R Blood, Rick R Burke, and Nathan Lanci vi Round-Robin Testing of European-Weight Fire f ghting Clothing with Fire Engulfment Instrumented Mannequins 351 J D Dal e, S A Paskal uk, and E M Crown Why Does the Structural Integrity of Flame-Resistant Protective Clothing Hang by a Thread? 374 Vincent Diaz Back Protector Performance—Standard Methodologies Versus Realistic Testing Jean-Phil l ippe Dionne, M ing Cheng, Je f Levine, M atthew Keown, and Aris M akris vii 391 Overview Th s volume contains a collection of 23 peer-reviewed papers from the Tenth Symposium on Performance of Protective Clothing and Equipment held January 28–29, 2016, in San Antonio, TX e event was the tenth in an ongoing series of ASTM Committee F23 symposia that has spanned 30 years e symposium theme, “Risk Reduction Th ough Research and Testing,” drew academic and industrial researchers alike with a common goal to increase protection for the users of all varieties of protective clothing and equipment e symposium was preceded by two very full days of standards development during a bi-annual meeting of ASTM Committee F23 on Personal Protective Clothing and Equipment To open the event, the symposium co-chairs invited Lieutenant Jim Reidy of the San Antonio Fire Department to deliver a welcome speech e lieutenant’s talk served as an excellent reminder to all those in attendance of the importance of ongoing research and testing and gave a personal connection to an end user whose life ofen depends on our success Te overall objective of the symposium was to provide a forum for discussing the current state and future of the personal protective clothing and equipment industry Specific bjectives included: T T T T • • • • Showcase current research and advances in personal protective clothing and equipment Defi e and discuss challenges facing those developing, testing, and using personal protective clothing and equipment Promote communication and information sharing between researchers, manufacturers, users, and government agencies Assess the need for new and/or revised standards Although many of the presentations covered topics involving fame exposures, the symposium co-chairs were pleased to welcome several discussions on the topics of chemical and biological protection, arc fash protection, and blast protection for military and law enforcement Te span of topics also shed light on important emerging issues, including a better understanding of physiological impact of protective clothing, and innovative ways to reduce heat stress Particularly useful for the F23 Committee members in attendance were the topics focusing on improving upon existing test methods to better serve the protective clothing industry ix 392 STP 593 On Performance ofProtective Clothing and Equipment th a t sta nd a rds req u i rements (N I J , BS EN , or others) mu st on l y be perceived a s mi n i mu m req u i rements for spi n e protecti on , keepi ng in mi n d tha t rea l i sti c i n ci d en ts a re l i kel y to yi el d mu ch more severe i m pa cts for wh i ch a h i g h er l evel of protecti on ma y be req u i red Keywords spi ne protection, drop testing, performance standard, bomb suit, impact inj ury I ntroduction Explosive ordnance disposal (EOD) suits, also referred to as bomb suits, typically focus on frontal protection This is due to the standard operating procedures requiring a frontal approach to the explosive devices However, spine protection is also essential to mitigate impact severity arising from certain falls, from the body being ejected toward rigid obstacles due to a frontal blast or an unexpected secondary blast from any direction As such, the Public Safety Bomb Suit Standard from the U.S National Institute of Justice (NIJ-0117.00) [1] includes a spine impact protection requirement that must be met for bomb suit models to be certified As per this standard, the protection offered must cover at least the top of the T1 vertebra to at least the bottom of the L5 lumbar vertebra and shall have a minimum width of 20.3 cm The associated test method is based on a drop tower test methodology, whereby a spine protector (which can be extracted from a bomb suit) is hit by a hemispherical-shaped impactor while resting on a force platform The NIJ threshold (pass/fail) values have been determined through drop tower testing of actual bomb suit spine protectors The spine protection requirements from the NIJ bomb suit standard are similar to those found in the BS EN-1621-2 standard for motorcycling spine protectors [2] Unfortunately, both the NIJ-0117.01 and the BS EN-1621-2 standards have no biomechanical basis, and as such, their relevance toward the selection of appropriate spine protectors has yet to be proven There exist only a few injury criteria related to the spine, such as the maximum lumbar force compression of 6.7 kN [3] and the maximum 3-ms spine acceleration clip [4] Unfortunately, these injury criteria have been developed for impact conditions that are not relevant to EOD scenarios (such as a fall on rigid obstacles after being propelled) The lumbar force maximal compression is used in conditions where the spine is compressed axially, while the 3-ms spine acceleration clip was derived for frontal impacts in automobile accidents The Dynamic Response Index (DRI) [3] is another criterion dealing with spine injuries Although the most widely used version of the DRI involves the axial loading of the spine (DRI-z) and is not relevant to this work, the DRI-x version of this criterion is relevant because it considers the loading of the spine perpendicular to the back surface in a direction going through the body from the back to the front (or vice versa) A research paper focused on helicopter seating tests [5] provides injury thresholds for the DRI-x DIONNE ET AL., DOI 10.1520/STP159320160007 In addition, a study related to impacts perpendicular to the back surface from Bass et al [6] will be briefly discussed in the context of this paper The obj ective of this study will be to compare current requirements from spine protection standards with existing inj ury criteria and to force data from both experimental tests and numerical simulations toward suggesting potential enhancements in standard test methodologies, focusing on impactor mass and geometry, impact energy, and impactor material Previous Studies In a recent study [7] , three sets of experimental spine protector tests were conducted: drop tower, more realistic tests involving localized baseball bat blows, and mannequins free-falling on their backs Although the two realistic tests (baseball bat blows and free fall) involved the same Hybrid III fiftieth percentile male anthropomorphic mannequins, thus allowing a direct comparison, the drop tower tests did not involve a mannequin As such, commenting on the drop tower test methodology based on the results from the mannequin tests involved estimating impact energies for the other two cases For the baseball bat case, the energy was calculated using the bat’s rotational velocity at impact and its moment of inertia For the freefall case, the energy could not be computed without the knowledge of the effective mass of the falling mannequin An experimental study has been conducted in the past in the context of snowboarding spine protectors [8] That study highlighted the fact that the only recognized test methodology for back protectors was the BS EN-1 621 -2 standard, which might not be relevant for snow sports applications, but no alternative was available Relative Spine Protector Performance at Different Loadings Personal protective designs can be optimized toward meeting specific standard requirements through the selection of materials exhibiting desired properties (e.g., stress-strain behavior) As such, test parameters used in standards (e.g., impact energy, maximum transmitted force, impactor mass) must be carefully selected because they will influence personal protective equipment (PPE) design Performance standards also are commonly used to compare the effectiveness of different protective solutions However, it is common for solutions based on different materials and constructions to vary in performance in such a way that, although Solution A outperforms Solution B for a specific threat, the situation is reversed at a different threat level This further emphasizes the need to appropriately define the impact testing standard parameters Fig provides a comparison in the specific context of spine protectors Two prototype spine protectors (referred to as Solution A and Solution B) were tested using the NIJ-01 7.00 methodology at different energy levels Both solutions 393 394 STP 1593 On Performance ofProtective Clothing and Equipment FIG Comparing the performance of two protective solutions at different energy levels Solution A outperforms Solution B at 45 J, but the trend is reversed at higher-impact energies consisted of all bomb suit materials, including soft ballistics and outer-layer fabrics, as mandated by the NIJ standard At an impact energy of 45 J (also dictated by the NIJ standard), Solution A outperforms Solution B by exhibiting a lower transmitted force However, the situation was reversed for tests conducted at energies of 75 and 1 J, with a significant difference observed for the 1 0-J tests where Solution B now outperforms Solution A The results from Fig thus clearly emphasize the importance of carefully selecting the impact energy because it affects the relative ranking of protective solutions Determining which solution performs better for the application depends on which energy level is deemed better suited to actual threats the protective equipment must protect against Although the current NIJ-01 7.00 and BS EN 621 -2 standards both suggest a single-impact energy level, it can be argued that, in some cases, more than one energy level should be tested PPE must provide protection against both the infrequent large impacts potentially yielding severe injuries and against the more frequent weaker impacts more likely to yield minor injuries The selection of impact energy and acceptable transmitted force must therefore be based on the frequency and severity of threats as well as on the tolerable impact levels (injury thresholds) for the human body Effect of Impactor Mass—Experimental Tests In the previous section, the impact energy was used as a proxy for impact severity However, the transmitted force also depends on the impactor mass The NIJ-01 17.00 and BS-EN 621-2 standards both use a similar impact energy (45 and 50 J, DIONNE ET AL., DOI 10.1520/STP159320160007 respectively), but they require a different impactor mass (1 46 and 5.00 kg, respectively) As a result, for a given impact energy, the impact velocity, and hence the linear momentum, will differ To illustrate the effect of impactor mass, Fig shows transmitted force results for impacts delivered on spine protectors (Solutions A and B) at a constant 45-J impact energy but using different impactor masses, ranging from 68 to 4.03 kg (NIJ-01 7.00 test methodology otherwise adopted) One can see that no significant effect of impactor mass is observed for both protective solutions However, the impactors tested are lightweight compared to the more realistic case of a mannequin being dropped on its back According to Bass et al [6] , an effective mass of 28 kg can be used for free-fall tests representing a human body The next section extrapolates the experimental results from Fig to larger impactor masses using numerical simulations Effect of Impactor Mass—Numerical Simulations Due to the physical limitations of the drop tower test setup used for the tests illustrated in Fig , the larger impactor mass tested weighed only 4.03 kg This impactor mass is significantly lower than the mass of a full-body Hybrid III anthropomorphic fiftieth-percentile male mannequin (approximately 70 kg) or even the effective mass proposed by Bass et al [6] for free-fall simulations of humans on their backs (28 kg) As such, numerical simulations were conducted to extend the range of transmitted force results at a constant energy value of 45 J to higher impactor masses FIG Effect of impactor mass on transmitted force for a constant 45-J impact energy (experimental results based on the NIJ-0117.00 standard) 395 96 STP 1593 On Performance ofProtective Clothing and Equipment FIG I m p a ct o r a n d tests a n vi l d i cta ted b y th e N I J - 1 0 s ta n d a rd fo r s p i n e p ro t e c t o r N o t e t h a t t h e c y l i n d e r re s t s a b o ve t h e t w o s u p p o rt w i n g s The model used was developed using LS-Dyna, an advanced general-purpose multiphysics simulation software package developed by the Livermore Software Technology Corporation The model includes four parts: impactor, sample, anvil, and load cell ( Fig 4) The test sample is composed of a relative rigid composite sheet 3.175 mm thick and a 25.4-mm-thick foam-type shock attenuation panel All parts are modeled using constant stress eight-node hexagonal elements except the composite sheet that is modeled with Belytschko-Tsay four-node shell elements Appropriate hourglass controls are applied to control hourglass energy Symmetries were leveraged to reduce the size of the model As such, only a quarter of the 210 mm by 300 mm sample panel was modeled to simulate the impact event The impactor and anvil are modeled with the dimensions designated in the Canadian Standards Association (CSA) Z617-06 standard [9] As a result, the forces calculated are only a quarter of the total force (adjusted values presented in this paper) The impactor and anvil are made of aluminum alloy, while the load cell is made of steel These three parts are modeled with the *MAT_PLASTIC_KINEMATIC LS-Dyna subroutine The materials from the spine protector dominate the output of the simulation The stress versus strain curve for the foam-type material is shown in Fig No effort was made to accurately model either Solution A or Solution B from the previous section Instead, a generic material with stress-strain curve, illustrated in Fig 5, was implemented As such, only trends are investigated through the numerical simulations; there are no direct comparisons with the experimental data Fig provides an illustration of the model at maximum compression for the case of a 1.4-kg impactor hitting the spine protector with an impact energy of 45 J DIONNE ET AL., DOI 10.1520/STP159320160007 FIG Numerical model of the impactor and anvil from Fig as implemented for numerical simulations of transmitted force Support wings from Fig are not modeled The maximum Von Mises stress observed throughout the spine protector is 1.18 MPa, indicating that the foam-type material has been compressed up to its solidifying stage Transmitted forces from simulations are filtered using a four-pole Butterworth low-pass filter with a cut-off frequency of 500 Hz to remove oscillations due to structural vibration and numerical noises Fig provides the peak transmitted force FIG Stress-strain curve for the foam-type material used in the impact simulations 97 98 STP 1593 On Performance ofProtective Clothing and Equipment FIG Maximum compression for a 1.4-kg impactor with an impact energy of 45 J Maximum Von Mises stress is 1.18 MPa results for 45-J drop tower impacts as a function of impactor mass for the range of impactor masses used experimentally (as shown in Fig ) Similar to the experimental results, the peak transmitted force values were found to vary only minimally, without showing a definite trend (either up or down) Thus, the trend observed numerically was validated by the experimental results However, when the impactor mass was increased further, up to masses more representative of an actual human being (up to 1 kg here), an increase in peak transmitted force was clearly seen ( Fig 8) Comparing the two extremes (1 and 1 kg), the peak transmitted force was increased more than three-fold Keeping in mind that the impact energy was kept constant at 45 J, this indicates the key role played by the FIG Peak transmitted force versus impactor mass for 45-J simulated impacts (LS Dyna) DIONNE ET AL., DOI 10.1520/STP159320160007 FIG Peak transmitted force versus impactor mass for 45-J simulated impacts (LS Dyna) across a wider range of impactor masses impactor mass and, hence, the linear momentum (or impulse) For a constant impact energy, the linear momentum at impact increases with impactor mass Fig provides transmitted force versus time traces for all impactor masses simulated Of note is the significant increase in impact duration as the impactor mass increases, as well as the location of the peak moving toward the “right” compared to the center of the signal This was due to the reduced impact velocity as the mass increases Effect of Impactor Energy—Numerical Simulations As one would expect, the impact energy (for a given impactor mass) plays a significant role in the peak transmitted forces calculated, where the impact energy FIG Transmitted force versus time traces for 45-J simulated impacts (LS Dyna) across a wider range of impactor masses 399 400 STP 1593 On Performance ofProtective Clothing and Equipment increases linearly with the drop height and square of the velocity at impact Fig 10 shows the results from numerical simulations conducted at three different energy levels: 45 J (per the NIJ 01 7.00 standard) , 75 J (as required by some end- user groups) , and 1 J (close to the maximum limit for the experimental drop tower apparatus shown in Fig ) Fig 10 shows peak transmitted forces for three impactor masses: kg (corresponding to the NIJ 01 00 standard) , kg (corresponding to the BS- EN 621 - standard but for an energy of 50 J) , and kg (close to the 28- kg value suggested by Bass et al [6] as an effective mass for humans falling on their backs) The fourth curve represents the full human weight—here taken as the weight of a fiftieth-percentile Hybrid III male mannequin of approximately 70 kg The strong dependence on impact energy suggests that this impact parameter, together with the corresponding acceptable peak transmitted force, must be picked carefully to be representative of actual threats Realistic Free Falls Versus Injury Threshold and Impact Energy Previous sections have focused on the role of impactor mass and energy in affecting the transmitted force, without investigating how realistic or representative these energy and force values are as compared to actual impact events To determine representative force and energy values, the results from a previous study [7] are used for a free- falling mannequin; photos of the test setup are shown in The maximum drop height (shown in Fig 11 ) Fig 11 and Fig 12 had been selected to generate an impact velocity typical of a fall on the ground after having been subj ected to the blast of a large explosive (approximately - m drop height for a 5.4- m/s impact velocity) The free- fall tests were conducted by dropping an instrumented fiftiethpercentile Hybrid III male mannequin using a Precision Drop Tester (Lansmont, CA) that simulated free falls on the ground This machine, once triggered, generates obstacle- free, friction- free falls, with minimal sideways displacements FIG 10 Peak transmitted force versus impact energy for four representative impactor masses DIONNE ET AL., DOI 10.1520/STP159320160007 FIG 11 Photo of the test setup used by Dionne et al [7] A spine protector sample is used; drop height: 1.51 m Using an effective mass of 28 kg per the suggestion of Bass et al [6], the corresponding impact energy for this 5.4-m/s impact is 408 J This energy value far exceeds the impact energies used in either the NIJ 0117.00 or BS EN 1621-2 standard test methods (45 and 50 J, respectively) A fall from such a height might be FIG 12 Photo of the test setup used by Dionne et al [7] A spine protector sample is used; drop height: 0.40 m 401 402 STP 1593 On Performance ofProtective Clothing and Equipment considered as too severe a threat for a protective component to be tested against A more benign threat was also tested ( Fig 12 ), corresponding to a drop height of 0.40 m (impact velocity: 2.8 m/s) The impact energy associated with this drop height is 1 J This value is more in line with impact energies used in the two standards, but one might argue that the threat (drop height lower than the center of gravity) is not severe enough Measurements of interest made during these tests are the DRI-x values (not reported in Dionne [7] ) and the measured lumbar forces (x-direction) measured using the mannequin instrumentation These results are presented in Table The injury threshold for the DRI-x published in Jackson et al [5] is DRI-x ¼ 35 for a low risk of injury and 40 for a moderate risk of injury (for positive values of DRI-x) All DRI-x values listed in Table are below the low risk of injury but very close in the 51 -m drop case, indicating that this drop height is indeed a severe impact configuration The DRI-x values corresponding to the 0.4-m drop height are much lower, not exceeding No references could be found for an injury threshold corresponding to the lumbar force in the x-direction (such an injury threshold exists for the lumbar force in the y-direction) Discussion Ideally, the “input” impact parameters (impactor mass and velocity—hence, energy) should be representative of the threats being faced In addition, the passing threshold for transmitted force should have a biomechanical basis (link with injury thresholds) Table summarizes the impact parameters from standards (NIJ01 7.00, BS-EN 621 -2, and an unpublished government client requirement) as well as results from experiments and numerical simulations Assuming that the 0.40-m drop experiment is representative of a field threat against which spine protectors should provide protection, one should aim for a standard test that would involve a similar impactor mass (effective mass of 28 kg as reported by Bass et al [6] ) and impact energy (approximately 00 J) The 28-kg impactor mass is far in excess of the impactor masses currently used by existing TABLE Lumbar forces and DRI-x values measured during free falls of Hybrid I II fiftieth-percentile mannequins with a prototype spine protector Test Condition 0.4-m drop height (6 tests) 1.51-m drop height (6 tests) Impact Energy (J) 110 408 Lumbar Fx (kN) DRI-x Average 1.29 15.4 Min 1.59 13.7 Max 1.01 16.8 Average 2.12 31.3 Min 1.60 30.7 Max 2.79 32.4 DIONNE ET AL., DOI 10.1520/STP159320160007 standard methodologies On the other hand, one of the simulation scenarios did involve a very similar impactor mass of 30 kg, with an impact energy of 1 J, closely matching the 0.40-m drop height requirement (last row of Table The configuration listed in the last row of Table 2 ) (impactor mass of 30 kg and impact energy of 1 J) would therefore seem appropriate However, dropping a 30-kg mass from a drop tower test apparatus might push the limits of acceptable weight drops in most test facilities Mandating such a large impactor mass in a standard therefore might severely limit the number of potential test facilities that could conduct the test But beyond this practical laboratory limitation, one must also consider the resulting transmitted forces Although the 30 kg–1 J scenario matches the representative 0.40-m free-fall height in terms of “input threat,” the transmitted force of 25.8 kN (keeping in mind that the materials models were not aimed at modeling the exact materials used in the mannequin free-fall experiments) is very high compared to the transmitted forces measured in the free-fall mannequin tests (factor of 0) Ideally, the standard test methodology should subject the protective components to a similar level of compression (hence, transmitted forces) that would be seen in representative impacts from the field It can be assumed that the transmitted forces measured with the mannequins would be similar to those that would have been measured through the spine protector materials As such, based on the lumbar force values recorded with the mannequins (1 29 and 2.1 kN) —corresponding to noninjurious DRI-x values, acceptable transmitted forces for a standard test method TABLE Summary of impact parameters (standards, experiments, simulations) Result Type Spine protector standards (drop tower) Mannequin freefall experiments Drop tower numerical simulations Configuration NIJ-0117 [1] BS-EN 1621-2 [2] (Level 2) Unpublished government requirement 0.40-m drop height [7] 1.51-m drop height [7] Based on NIJ-0117 [1] Energy based on NIJ, impactor mass ? effective mass from Bass et al [6] Energy based on unpublished government requirement, impactor mass ? effective mass from Bass et al [6] Energy close to 0.40-m mannequin free-fall drop, impactor mass ? effective mass from [6] Impactor Mass Impact Velocity Impact Energy Transmitted Force 1.46 kg kg 1.46 kg 7.99 m/s 4.47 m/s 10.3 m/s 45 J 50 J 75 J kN kN kN 28 kg 28 kg 1.46 kg 30 kg 2.8 m/s 5.4 m/s 7.99 m/s 1.73 m/s 110 J 408 J 45 J 45 J 1.29 kN 2.12 kN 4.36 kN 5.44 kN 30 kg 2.24 m/s 75 J 16.3 kN 30 kg 2.77 m/s 115 J 25.8 kN 403 404 STP 1593 On Performance ofProtective Clothing and Equipment should probably not exceed kN Otherwise, the protective materials would end up being much further compressed than what is to be realistically expected in actual field events As such, an ideal standard test methodology would involve a 30-kg impactor mass, dropped to generate approximately 1 J, and would result in spine protector transmitted forces of no more than kN However, the experimental tests shown in Fig and Fig , involving much lower impactor masses and impactor energy, did generate transmitted forces far in excess of kN This is most likely due to the fact that the impactors and anvils used in standard testing are made of metal (typically steel or aluminum) Metallic materials are not representative of the human body (or the Hybrid III mannequin) Moreover, drop tower tests involved localized impacts, compared to the mannequin free-fall experiments for which a much larger area contributes to mitigating the impact, thus limiting the total transmitted force A possible recommendation for defining a better test methodology would be to replace the metallic anvil with a softer material that would be more representative of the human body and that would result in lower transmitted forces Anvil material could be wood or rubber However, it might prove challenging to carefully define anvil material properties while ensuring that the anvil integrity is maintained for a large number of tests The impactor area should also be significantly increased to better represent the area of the back involved in free falls, also contributing toward generating lower transmitted forces However, should changes in anvil materials prove too challenging, then the current metallic anvil and impactor materials should be kept In that case, the focus should be on a test method that limits the transmitted force to not too far beyond kN (approximate maximum value measured for mannequin free-fall tests) Otherwise, protective materials are likely to be compressed much further than is to be expected realistically For that purpose, the current NIJ-01 7.00 method might represent an acceptable compromise, even though its impactor mass (1 46 kg) and its impact energy (45 J) are low compared to realistic threats At the very least, the NIJ-01 7.00 standard methodology generates transmitted forces more in line with what is to be expected in the field for the spine protector Conclusion The ideal impact parameters for a spine protector test method would involve an impactor mass of approximately 30 kg with an area covering a good portion of the back protector, an impact energy of approximately 1 J, with a soft anvil material that would result in transmitted forces of the order of no more than kN However, given the practical limitations of test facilities in terms of maximum impactor mass and the challenges associated with using and validating anvils with soft materials, standard test methodologies should focus on ensuring that measured transmitted forces not deviate too much from a kN maximum Subjecting spine protectors DIONNE ET AL., DOI 10.1520/STP159320160007 to excessive, transmitted force levels might result in rej ecting systems that are likely to provide a good level of protection in more realistic field use and in designing systems optimized for an unrealistic threat level To ensure that spine protectors provide protection across a broad range of impact severity, another impact energy level could also be selected Further experimental studies should be conducted investigating anvil materials and impactor masses and shapes Finally, investigations of inj ury thresholds relevant to back-loading in the x-direction in impact severity ranges relevant to EOD would provide further j ustification for the selection of specific transmitted force levels to be used in protection standards References [1 ] Public Safety Bomb Suit Standard , NIJ Standard-0117.00, U.S Department of J u sti ce, Offi ce of J usti ce Prog rams, Washi ngton, DC, M arch 201 [2] Motorcyclists’ Protective Clothing Against Mechanical Impact, Part 2: Motorcyclists’ Back Protectors—Requirements and Test Methods, Bri ti sh Stand ard s I nsti - BS EN 621 -2: 2003, tuti on, London, UK, 2003 [3] “Test M ethod ol ogy for Protecti on of Vehi cl e Occu pants Ag nst Anti -Vehi cul ar Land mi ne Effects,” [4] TR-HFM-090, N ATO Research 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