4


Combat Helmet Testing

4.0 SUMMARY

This chapter describes how combat helmets are tested. It includes a brief summary of the testing process, a description of the test threats, and a discussion of the various sources of variation in the testing process.

4.1 INTRODUCTION

Federal government departments and agencies are required to “develop and manage a systematic, cost-effective government contract quality assurance program to ensure that contract performance conforms to specified requirements” (Title 48 of the Code of Federal Regulations, subpart 246.1) (CFR, 2013). In particular, first article testing (FAT)1 is conducted to ensure that “the contractor can furnish a product that conforms to all contract requirements for acceptance” (FAR, 2013). Once a contractor has passed FAT and begins production, lot acceptance tests (LAT)2 are used to assess whether combat helmets continue to conform to contract requirements during regular production.

As part of FAT and LAT, combat helmets are subjected to a series of ballistic and nonballistic tests. Ballistic tests assess the helmet’s ability to prevent penetration and limit helmet deformation to a given threshold. Nonballistic tests assess other helmet capabilities, including impact resistance, pad compression durability, coating adhesion durability, and helmet compression resistance testing. Helmets are also subjected to a series of inspections, such as whether the shell dimensions meet those specified in the purchase description. All of these tests and inspections are intended to assess whether a particular manufacturer’s product conforms to the government’s contract specifications as outlined in the purchase description (U.S. Army, 2012).

The goal of testing is to determine if the helmet is of acceptable quality based on a limited test sample. Not every helmet can be tested because the tested helmet is damaged in the testing process. Hence, decisions about the larger collection of helmets must be based on a limited test sample. Because only a sample of helmets can be tested, the resulting test conclusion is subject to uncertainty and unavoidable risks to both the Department of Defense and the manufacturer. Test protocol design requires making trade-offs between risks for both groups. The size of the risk for each group arises because of the test design and any limitation on resources.

4.2 BALLISTIC TESTING METHODOLOGY

The helmet ballistic testing methodology has been derived from existing body armor testing methods. The methodology for ballistic testing for body armor follows from testing done in the late 1970s by Prather et al. (1977) that, however tenuously, connects the current body armor methods and the test measures to some evidence of injury (NRC, 2010, 2012). For combat helmets, however, the current testing methods and measures have no connection to research on head and brain injury. The lack of connection between injury and current test methods and measures is a significant concern.

Test Processes

During a test, the helmet being tested is affixed to a headform packed with modeling clay, and a rifle-like device is used to fire various projectiles into the helmet. The clay is used as a recording medium for: (1) assessing penetration should the projectile or portions thereof pass through the helmet into the clay, and (2) measuring the deformation of the helmet, where an impression is left in the clay surface as a result of the ballistic impact pushing the helmet into the clay. Electronic instrumentation is used to measure projectile velocity before impact. Appendix E describes the ballistic testing process in more detail.

 

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1The current DOT&E protocol for combat helmet first article testing is reprinted in Appendix B.

2The current DOT&E protocol for combat helmet lot acceptance testing is reprinted in Appendix B.



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4 Combat Helmet Testing 4.0  SUMMARY The goal of testing is to determine if the helmet is of acceptable quality based on a limited test sample. Not every This chapter describes how combat helmets are tested. It helmet can be tested because the tested helmet is damaged includes a brief summary of the testing process, a description in the testing process. Hence, decisions about the larger col- of the test threats, and a discussion of the various sources of lection of helmets must be based on a limited test sample. variation in the testing process. Because only a sample of helmets can be tested, the resulting test conclusion is subject to uncertainty and unavoidable risks 4.1  INTRODUCTION to both the Department of Defense and the manufacturer. Test protocol design requires making trade-offs between risks Federal government departments and agencies are required for both groups. The size of the risk for each group arises to “develop and manage a systematic, cost-effective govern- because of the test design and any limitation on resources. ment contract quality assurance program to ensure that contract performance conforms to specified requirements” (Title 48 of the Code of Federal Regulations, subpart 246.1) 4.2  BALLISTIC TESTING METHODOLOGY (CFR, 2013). In particular, first article testing (FAT)1 is con- The helmet ballistic testing methodology has been derived ducted to ensure that “the contractor can furnish a product from existing body armor testing methods. The methodology that conforms to all contract requirements for acceptance” for ballistic testing for body armor follows from testing done (FAR, 2013). Once a contractor has passed FAT and begins in the late 1970s by Prather et al. (1977) that, however tenu- production, lot acceptance tests (LAT)2 are used to assess ously, connects the current body armor methods and the test whether combat helmets continue to conform to contract measures to some evidence of injury (NRC, 2010, 2012). For requirements during regular production. combat helmets, however, the current testing methods and As part of FAT and LAT, combat helmets are subjected measures have no connection to research on head and brain to a series of ballistic and nonballistic tests. Ballistic tests injury. The lack of connection between injury and current test assess the helmet’s ability to prevent penetration and limit methods and measures is a significant concern. helmet deformation to a given threshold. Nonballistic tests assess other helmet capabilities, including impact resistance, pad compression durability, coating adhesion durability, Test Processes and helmet compression resistance testing. Helmets are During a test, the helmet being tested is affixed to a also subjected to a series of inspections, such as whether headform packed with modeling clay, and a rifle-like device the shell dimensions meet those specified in the purchase is used to fire various projectiles into the helmet. The clay description. All of these tests and inspections are intended to is used as a recording medium for: (1) assessing penetration assess whether a particular manufacturer’s product conforms should the projectile or portions thereof pass through the to the government’s contract specifications as outlined in the helmet into the clay, and (2) measuring the deformation of purchase description (U.S. Army, 2012). the helmet, where an impression is left in the clay surface as a result of the ballistic impact pushing the helmet into the 1The current DOT&E protocol for combat helmet first article testing is clay. Electronic instrumentation is used to measure projectile reprinted in Appendix B. velocity before impact. Appendix E describes the ballistic 2The current DOT&E protocol for combat helmet lot acceptance testing is reprinted in Appendix B. testing process in more detail. 25

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26 REVIEW OF DEPARTMENT OF DEFENSE TEST PROTOCOLS FOR COMBAT HELMETS TABLE 4-1 DOT&E First Article Testing Helmet Test Matrix for the Advanced Combat Helmet V50 Ambient Hot Cold Seawater Weatherometer Accelerated Aging 2-grain 1 V50 1 V50 1 V50 1 V50 Size: Small Size: Medium Size: Large Size: XL 4-grain 1 V50 1 V50 1 V50 1 V50 Size: XL Size: Small Size: Medium Size: Large 16-grain 1 V50 1 V50 1 V50 1 V50 Size: Large Size: XL Size: Small Size: Medium 17-grain 1 V50 1 V50 1 V50 1 V50 1 V50 1 V50 Size: Medium Size: Large Size: XL Size: Small Size: Large Size: Medium 64-grain 1 V50 1 V50 1 V50 1 V50 Size: Large Size: XL Size: Medium Size: Small Small arms 1 V50 1 V50 1 V50 1 V50 1 V50 Size: Medium Size: Small Size: XL Size: Large Size: Medium 9-mm RTP/BTD 60 shots 60 shots 60 shots 60 shots shell 12 helmets 12 helmets 12 helmets 12 helmets Sizes: Sizes: Sizes: Sizes: Small: 3 Small: 3 Small: 3 Small: 3 Medium: 3 Medium: 3 Medium: 3 Medium: 3 Large: 3 Large: 3 Large: 3 Large: 3 XL: 3 XL: 3 XL: 3 XL: 3 9-mm RTP 17 shots 16 shots 16 shots 16 shots hardware 9 helmets 8 helmets 8 helmets 8 helmets Sizes: Sizes: Sizes: Sizes: Small: 2 Small: 2 Small: 2 Small: 2 Medium: 3 Medium: 2 Medium: 2 Medium: 2 Large: 2 Large: 2 Large: 2 Large: 2 XL: 2 XL: 2 XL: 2 XL: 2 Small arms RTP 17 shots 16 shots 16 shots 16 shots 17 helmets 16 helmets 16 helmets 16 helmets Sizes: Sizes: Sizes: Sizes: Small: 4 Small: 4 Small: 4 Small: 4 Medium: 5 Medium: 4 Medium: 4 Medium: 4 Large: 4 Large: 4 Large: 4 Large: 4 XL: 4 XL: 4 XL: 4 XL: 4 NOTE: BTD, ballistic transient deformation; RTP, resistance to penetration; V 50, velocity at which the probability of penetration is 0.5; XL, extra large. SOURCE: DOT&E (2011). There are two types of measurements that are made on the For FAT, as shown in Table 4-1, 48 helmet shells are tested helmet: (1) whether the bullet penetrates the helmet or tested against the Remington 9-mm threat, and 35 helmets not (called resistance to penetration [RTP]); and (2) if there are tested for hardware. Another 65 helmets may be tested is no penetration, a surrogate measure of the deformation of against a small arms threat (which is classified). In addition, the helmet referred to as the backface deformation (BFD). 27 helmets are tested for V50. Table 4-1 specifies both the These measures are formally defined in Chapter 5. size of the helmet (small, medium, large, and extra large) Per the Director, Operational Test and Evaluation and whether the helmet is exposed to a particular environ- (DOT&E) protocol, the test is conducted as a sequence of ment, such as ambient, hot, cold, seawater,3 weatherometer five ballistic impacts: one each to the front, rear, left, and (accelerated test to mimic long-term exposure to weather), right sides of the helmet and to the helmet crown. Both pen- and other types of accelerated aging. Under the DOT&E etration and BFD, a measure of the indent in the clay caused protocol, within each set of tests (shell, hardware, and small by the ballistic forces from the bullet, are measured. Current protocol also tests the V50 ballistic limit using a series of 6 to 3The helmets the Army procures are used DoD wide, including both the 14 shots to the five regions of the helmet at varying velocities Navy and the Coast Guard. Soldiers wearing helmets may also find them- per MIL-STD-622F (DoD, 1987). (See Chapter 9 for further selves in a maritime environment while on Navy support troop-carrying discussion of the methodology for estimating V50.) vessels. The purpose of testing helmets that have been conditioned by seawater is to determine if the helmet material can withstand exposure in that environment without degraded ballistic performance.

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COMBAT HELMET TESTING 27 arms), the results are combined across the helmet sizes and it may be tested against an unspecified small arms threat.5 environments to assess whether FAT is passed or failed. The The helmet is also tested for V50, the velocity at which the details are described in Chapters 5 and 6. helmet is equally likely to stop or not stop an object, such The current DOT&E testing methodology is based on a as the following: number of assumptions, including the following: • 2-grain right-circular-cylinder (RCC) fragment, • Shots are independent. In FAT and LAT each helmet • 4-grain RCC fragment, is shot five times in five separate locations. The • 16-grain RCC fragment, resulting analyses treat these shots as independent, • 64-grain RCC fragment, and, combining all the shots across the helmets to assess • 17-grain fragment simulating projectile (FSP) RTP performance. This practice minimizes the num- (DOT&E, 2011).6 ber of helmets tested so that, to the extent that RTP failure is a rare, helmet-level event, this practice The ACH purchase description further specifies minimum decreases the chances of selecting a defective helmet V50 velocities for the above RCC and FSP test projectiles to test. That said, to the extent that the shots are truly (U.S. Army, 2012, p. 13). independent this is appropriate. On the other hand, to As discussed in Chapter 3, there are three general cat- the extent that they are not, this practice introduces egories of head injury threats: ballistic/fragmentation threats a bias in favor of soldier safety because helmets are from rapidly moving bullets or fragments; blunt threats from stressed beyond what is likely to occur in the field. impact into vehicle interiors, the ground, large slow frag- • Helmet performance is equivalent across testing ments, or other sources of head impact; and blast threats environments. In FAT, helmets are exposed to vari- from bombs, artillery, improvised explosive devices, and ous environments that include temperature extremes other explosive sources. Blast and fragmentation threats and other potential helmet stressors. The goal in from explosions historically have been the source of a large such testing is to ensure that the helmets perform majority of U.S. military wounding, while direct gunshot up to specifications in a variety of environments. wounds have decreased 46 percent relative to injuries with an Because the helmets exposed to these environments explosive source between Vietnam and Operation Enduring respond differently to either RTP or BFD, combin- Freedom and Operation Iraqi Freedom. ing the results across all the helmets is not precisely For the DOT&E LAT protocol, the shell and hardware are statistically correct. However, given the relatively required only to be tested against the Remington 9-mm, 124- small observed differences between environmental grain FMJ projectile (DOT&E, 2012). The ACH purchase conditions, it does not appear that this is likely a description further requires V50 testing for the 17-grain FSP major contributor to variability. (U.S. Army, 2012). • Data from predefined test locations sufficiently char- acterizes overall helmet performance. As described 4.3  SOURCES OF TEST VARIATION in Appendix E, helmets are tested in five precise locations, and thus it is implicitly assumed that the Variation in test measurement is an unavoidable part of results from these five locations adequately describe testing. In the ideal testing process, all observed variation in the performance of the helmet overall. From a pro- test measures is related directly and perfectly to the items cess variation perspective, this approach potentially being tested. In industrial quality control parlance, this is helps minimize testing variation. However, by defini- referred to as “part-to-part” variation. However, in the real tion, it also means that not all parts of the helmet are world, the testing process itself also introduces variation into tested, some of which are known to be weaker. For the test measurements. In terms of assessing the quality of example, the edges of the helmet are not tested, nor an item, this is the “noise” in the testing process. The goal of are the raised areas of the helmet around the ears. As a good testing process is to minimize these process-related such, the performance of the helmet in these regions sources of noise. The National Research Council Phase I is simply not observed during FAT and LAT.4 report (NRC, 2009, p. 12) noted that the “measurement system variance required for a test should be a factor of 10 or better than the total measured variation,” in order to have Test Threat Projectiles confidence that differences in the observed measurements For FAT, the helmet shell and hardware are tested against predominantly represent part-to-part (i.e., helmet-to-helmet) a Remington 9-mm, 124-grain full-metal-jacket (FMJ) differences. projectile (DOT&E, 2011), and per the DOT&E protocol, 5Kyle Markwardt, Test Officer, Aberdeen Test Center, “Helmet IOP PED-003 Briefing to NRC Helmet Protocols Committee,” presentation to 4See Chapter 9 for a discussion of assessing helmet performance at other the committee on March 22, 2013. locations during characterization testing. 6Ibid.

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28 REVIEW OF DEPARTMENT OF DEFENSE TEST PROTOCOLS FOR COMBAT HELMETS Helmet-to-helmet variability includes both variation the test process as the clay cools, and this can affect within and between helmet manufacturers. There are a BFD. number of additional sources of variation in the current test • Impact location variability arises to the extent that process, including the following: different locations on the helmet respond to the bal- listic impacts differently and/or if the order in which • Gauge-to-gauge (measurement) variability, which the locations are shot affects the test outcome. arises when there are accuracy or precision differ- • Environmental testing variability arises when the ences within or between the gauges used to measure various environmental conditions to which some of helmet performance. For helmet testing, the issue of the helmets are exposed (high and low temperature, gauge-to-gauge variation is largely associated with seawater, etc.) differentially affect the RTP and BFD the laser used to measure BFD, although it may performance of the helmets, and yet the helmets are also arise in other test-range measures such as those combined together for analysis. related to measuring projectile velocity, yaw, and obliquity. The current testing process seeks to control many of • Operator-to-operator variability, which arises when these sources of variation via the use of standardized testing the individuals conducting the test either execute procedures, accurate measurement instrumentation, and the the test differently or interpret test or measurement like. To the extent physically, analytically, and economically outcomes differently (or both). For helmet testing, possible, the more these sources of variation are controlled because V0 RTP testing is assessed visually, the the easier it is to distinguish signal (i.e., differences in hel- operator is the “gauge,” and thus the two types of met performance) from noise (i.e., variation in the testing variation are synonymous in this particular case. process). • Lab-to-lab variability arises when different laborato- Of course, testing costs time and money, and there are ries conduct helmet ballistic testing. Currently, only diminishing returns (and often increasing costs) in the pursuit the U.S. Army Aberdeen Test Center (ATC) conducts of increasingly precise test measurements. Furthermore, the helmet testing, so this type of variation is not appli- required level of measurement precision should be linked cable at this time, but it could be in the future. to and driven by the overall variation in the testing process • Environmental conditions variability arises to the where, for example, excessively precise measurements add extent that the testing is dependent on environmental little value to a testing process that is itself inherently highly conditions such as ambient test range temperature variable. Conversely, in any testing process, there should and humidity. Although the current ATC test is con- be a precision threshold that any measurement device must ducted in a temperature- and humidity-controlled test meet—again based on the overall variation of the testing range, the temperature and humidity can still vary process—to ensure that the measurement process itself does within specified constraints around nominal values. not add excessive variability to the test (NRC, 2012). As • Projectile velocity and impact variability arise from noted earlier, the previous NRC body armor reports recom- variation in individual shots. Much of this variability mend that variance attributable to the test measurement is controlled via the criteria that fair shots must be process should be less than one-tenth of the total measured within certain constraints on velocity, obliquity, yaw, variation (see NRC, 2009, p. 12; NRC, 2012, Appendix G; and location, but, as with the environmental condi- McNeese and Klein, 1991). tions, some residual variation remains within the range of the specified constraints. Finding 4-1. Some sources of test variation are relevant to • Test item configuration variability could arise in V0 the current helmet testing process while others are not. For helmet testing if helmet pads and other hardware example, given that tests are currently conducted only at differ if, for example, the helmet pads are installed ATC, lab-to-lab variability is not currently applicable. Simi- in different configurations or if the construction or larly, some sources of variation are directly observable with make-up of the pads themselves differs. existing data, and some are not. For example, as discussed in • Helmet-to-headform stand-off variability arises when Chapter 5, the test data show clear helmet size effects, impact one headform size is used to test multiple sizes of location effects, and minor environmental effects. helmets. This can result in differential stand-off dis- tances by helmet size, which can affect BFD. Finding 4-2. In the absence of more formal gauge repeat- • Clay variability arises because the clay formulation ability and reproducibility (R&R) studies, as well as other has changed over time and, as a result of this, the clay experimental studies, it is generally not possible to estimate now has to be heated in order to achieve historical the variation attributed to helmets that actually arises from rheological properties. However, because the clay is the other sources of variation listed above, such as the clay, now heated, its properties change over time during operators, and the laser.

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COMBAT HELMET TESTING 29 The NRC Phase III report on body armor noted the need for a formal gauge R&R study to determine the sources and magnitudes of variation in the test process (NRC, 2012, p. 10). To the best of the committee’s knowledge, such a study has not been done. Recommendation 4-1. The Department of Defense should conduct a formal gauge repeatability and reproducibility study to determine the magnitudes of the sources of test variation, particularly the relative contributions of the vari- ous sources from the testing methodology versus the varia- tion inherent in the helmets. The Army and the Office of the Director, Operational Test and Evaluation, should use the results of the gauge repeatability and reproducibility study to make informed decisions about whether and how to improve FIGURE 4-1 Clay time and temperature effects in the column the testing process. drop test. Each line represents the results of repeated column drop tests on a Figure 4-1 clay box, each of which was subject to different standard fixed environmental conditioning. Measurements were taken at times 3, 4.4  ADDITIONAL MEASUREMENT AND TESTING 18, 33, and 48, and the lines on the graph are linear interpolations ISSUES between the observed results at those time points. The graph shows Without delving into the specific details of the DOT&E that the depth of penetration systematically decreases over time as FAT and LAT protocols here (see Chapters 5-7), there are the clay cools. (See Appendix E for a description of the column drop test.) SOURCE: NRC (2010). two additional BFD measurement and testing issues of note: the use of clay as a BFD recording medium, and headform impacts on the measurement of BFD. Headforms Clay as a Recording Medium Army helmet testing is currently based on the ATC headform—derived from the National Institute of Justice As described in the Phase III report (NRC, 2012), there headform discussed in Chapter 3—with slots in the coro- is not much that is known about the use of clay as an impact nal and midsagittal directions (Figure 4-2). As more fully recording medium, including how accurately it records the described in Appendix E, the slots in the headform are backface signature of an impact and how much variation it packed with clay as the recording medium for both penetra- adds to the testing process. Thus it is unclear if the use of tion and BFD. There is currently one headform size, although clay is appropriate for helmet testing, particularly because there may be up to six helmet sizes (depending on the type “the mechanical backface response of the head surrogate may of helmet). govern both penetration and impact tolerance portions of the Two major issues with the headform may compromise its test” (NRC, 2012, p. 152). ability to appropriately and consistently measure BFD. First, One of the critical issues with the current clay (Roma the petals may impede the BFD of the helmet, which could Plastilina #1), as first noted in the NRC Phase II report (NRC, result in under-measurement of the actual ballistic transient 2010), is that the clay is time and temperature sensitive in deformation of the helmet. Second, as previously discussed, that, as Figure 4-1 shows, its properties can change signifi- with only one headform size, the stand-off distances may cantly over a 45-minute period as it cools. These effects are vary by helmet. Large helmets likely have a larger stand-off likely to affect BFD measurements. distance, whereas small helmets likely have to be forced onto The previous body armor committees studied many of the headform with minimal stand-off. the issues related to clay (NRC, 2012, 2010), and a detailed The Army is developing five new “sized” headforms examination of these issues is beyond the scope of this com- that will have a constant helmet shell-to-headform standoff mittee’s charge. But the committee notes that, purely from a distance for the Advanced Combat Helmet.7 As illustrated in testing process perspective, it is important to minimize this Figure 4-3, the motivation with the new sized headforms is to source of variation in the testing process. In particular, the eliminate one source of variation in helmet testing that arises Phase III body armor report recommended that DOT&E and because different sizes of helmets interact with the current the Army expedite the development of a replacement for the single-size headform in different ways. current Roma Plastilina #1 clay that can be used at room temperature (NRC, 2012). The committee notes that suc- cessful completion of this effort has the potential to remove 7James Zheng, Chief Scientist, Soldier Protective and Individual Equip- a significant source of testing variation and thus greatly ment, PEO Soldier, “Helmet Testing, Related Research & Development,” improve the testing process. presentation to the committee on March 22, 2013.

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30 REVIEW OF DEPARTMENT OF DEFENSE TEST PROTOCOLS FOR COMBAT HELMETS As described NRC (2012), the ATC headform has three potential problems. The first is that the solid aluminum pet- als constrain the flow of the clay during impact, which may result in a smaller BFD than otherwise would have occurred. The Peepsite headform reduces this possibility by eliminat- ing the metallic petals near the impact location. The second potential problem is that helmet backface con- tact can span the aluminum petals, either preventing further impact or altering the BFD response and backface signature recorded in the clay. As with the first problem, the lack of petals in the Peepsite headform eliminates the potential for this type of helmet-headform interaction, which may alter helmet backface response. The third potential problem arises because the clay and helmet have very different temperature characteristics. Using the current Roma Plastilina #1 clay, the clay is heated above room temperature to achieve the desired rheological behav- ior. Testing on the Peepsite headform, however, is done at room temperature, which means that the rate of cooling of the clay and the aluminum headform will be different, resulting in thermal gradients and residual strains and stresses in the clay that may affect the impact event (NRC, 2012). NRC (2012) noted that the Peepsite headform reduces the potential for a number of problems with the existing ATC headform. It further recommended that the Army should FIGURE 4-2 Aberdeen Test Center headform. SOURCE: NRC investigate the use of the Peepsite headform for use with the (2012). new room-temperature clay. That report indicated that the headform has the potential to improve testing compared to Finding 4-3. The implementation of new “sized” headforms the ATC clay headform using clay at elevated temperatures. by the Army represent an improvement in the helmet testing Figure 4-2 fixed process because the stand-off between helmet and headform 4.5  REFERENCES will be the same for all helmet sizes. CFR (Code of Federal Regulations). 2013. 48 CFR part 246–Quality Assur- ance. http://cfr.regstoday.com/48cfr246.aspx. Accessed April 1, 2013. The committee notes that these headforms were “reverse DoD (Department of Defense). 1987. Department of Defense Test Method engineered” from the existing helmets so that the stand-off Standard: V50 Ballistic Test for Armor. MIL-STD-662F. U.S. Army distances would all be exactly the same. It is not clear how Research Laboratory, Aberdeen Proving Ground, Md. anthropomorphically correct the new headforms are or how DOT&E (Director of Operational Test and Evaluation). 2011. Standardiza- closely they reflect the actual needs of soldiers and marines. tion of Combat Helmet Testing. Memorandum from J. Michael Gilmore, Director. September 20, 2011. Office of the Secretary of Defense, Washington, D.C. [reprinted in Appendix B] Recommendation 4-2. For future helmet development and DOT&E. 2012. Standard for Lot Acceptance Ballistic Testing of Military testing efforts, the Department of Defense should assess the Combat Helmets. Memorandum from J. Michael Gilmore, Director. importance of using anthropomorphically correct headforms May 4, 2012. Office of the Secretary of Defense, Washington, D.C. (as well as any other ballistic test dummies) based on head [reprinted in Appendix B] FAR (Federal Acquisition Regulations). 2013. Federal Acquisition Regula- sizes and proportions that appropriately characterize the tions, Subpart 9.3, Paragraph 9.302. First Article Testing and Approval. population that will wear the helmet. http://www.acquisition.gov/far/current/html/Subpart%209_3.html. Ac- cessed March 30, 2013. The “Peepsite”8 headform (Figure 4-4) was developed by McNeese, W., and R. Klein. 1991. Measurement systems, sampling, and the U.S. Army Research Laboratory to avoid the drawbacks process capability. Quality Engineering 4(1):21-39. NRC (National Research Council). 2009. Phase I Report on Review of the of the ATC headform, in particular, that the clay used to Testing of Body Armor Materials for Use by the U.S. Army: Letter measure BFD is located in between four solid aluminum Report. The National Academies Press, Washington, D.C. parts of the headform. NRC. 2010. Testing of Body Armor Materials for Use by the U.S. Army— Phase II: Letter Report. The National Academies Press, Washington, D.C. NRC. 2012. Testing of Body Armor Materials: Phase III. The National 8The “Peepsite” headform was developed at the Army Research Ex- Academies Press, Washington, D.C. perimental Facility Peep Site Range 20 at Aberdeen Proving Ground, Md.

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COMBAT HELMET TESTING 31 FIGURE 4-3 New Army “sized” headforms. SOURCE: James Zheng, Chief Scientist, Soldier Protective and Individual Equipment, PEO Soldier, “Helmet Testing, Related Research & Development,” presentation to the committee on March 22, 2013. Figrue 4-3 fixed FIGURE 4-4 Peepsite headforms: five headforms, one for each shot direction. SOURCE: Robert Kinsler, Survivability/Lethality Analysis Directorate, Army Research Laboratory, “The Peepsite Headform,” presentation to the committee on January 24, 2013. Prather, R., C. Swann, and C. Hawkins. 1977. Backface Signatures of Soft U.S. Army. 2012. Advanced Combat Helmet (ACH) Purchase Description, Figure 4-4 fixed Body Armors and the Associated Trauma Effects. ARCSL-TR-77055. U.S. Army Armament Research and Development Command Technol- Rev A with Change 4. AR/PD 10-02. Soldier Equipment, Program Executive Office—Soldier, Fort Belvoir, Va. ogy Center, Aberdeen Proving Ground, Md.