Theoretical Framework for the Sizing of Body Armor Plates to Optimize Fit
Authors: Choi-Rokas Hyegjoo , Garlie Todd , Blake Mitchell K. 
Published: June 2022

The development of optimized fitting body armor is critical to the fightability and protection of our warfighters and first responders. Body armor systems generally worn by warfighters consists of three protective portions: rigid plates, a soft armor insert, and a carrier/vest. Rigid plates are inserted into the front, back, and sides of the body armor to provide a higher level of protection for the wearer, while the soft armor is positioned behind the plates and in areas of the body where a lower level of protection is acceptable or required for mobility and comfort. Previously, a comprehensive fit mapping study on the family of armor plates to investigate the relationship between the coverage, anthropometry and mobility relative to size specifications of torso and side plates was conducted (Choi et. al., 2017). There is a delicate tradeoff between covering more (i.e., a greater area of protection) while not degrading the wearer’s mission performance (primarily their mobility). However, some level of mobility degradation is unavoidable. Choi et. al. (2017)'s results quantitatively defined the impact of coverage on mobility, visualized the mobility degradation as coverage increase, and set the allowable mobility degradation to be 10%. The coverage corresponding to the allowable mobility degradation was then converted into anthropometric dimensions. Accommodation envelopes for the current U.S. Army torso plates, relative to the male and female US Army population, were reported. Final size tariffs were calculated using the front plate. A sizing system for the back plate and/or side plates were not developed.This current study explores a theoretical framework for ballistic rigid plate size optimization for the front, back and side plates. When the protection coverage is maximized with minimal mobility degradation, the system would be considered optimized. For this study, minimal mobility degradation was set to 10%. For the front plate, Choi et. al. was revisited to retrieve the maximum width and length while limiting the mobility degradation to 10%. Chest Breadth, was measured using the ANSUR II (Gordon et. al., 2014) procedure, and Suprasternale -Tenth Rib Length was used to derive the width and length of plates, respectively. Then, a specification of the front ballistic plate, given anthropometric characteristics of the current U.S. Army population was developed from a reverse engineering approach. Theoretical accommodation envelopes for each front plate size were then developed and plotted against the current ANSUR II data. Once the front plate sizing system was developed, anthropometric characteristics of cases within each accommodation envelope per size were investigated to develop the required size specifications for the back plate. The width of the back plate shares the width of the matching front plate, but the length takes into account the back length, from the Cervicale -Tenth Rib Length. Size specifications for the side plates were also developed. Given that the front and back plates are worn together; the maximum width of the side plate is defined by the surface availability at the location of the tenth rib level. The side plate length is defined using the distance between Tenth Rib and the Axilla. A theoretical size system for a family of rigid armor plates is presented in a series of tables as well as bivariate plots. A detailed process for plate size prediction and the interaction between the front, back and side plates is presented.