An iterative and anthropometrically driven approach to body armor plate design for females

Abstract

The opening of combat arms positions to females, combined with innovative manufacturing processes allowing for increased curvature in rigid ballistic plates, allows the opportunity to design a body armor plate designed specifically for the female body. The current US body armor plates were developed from male torso shapes. This paper presents an iterative design and development process of female specific armor plates, based on the US Army anthropometric survey data (Gordon 2014) and rapid evaluation of prototyping designs.To understand the variation of female torso shapes, a female torso shape classification scheme was developed (Li, 2023), identifying nine torso groups for the US Army female population. For each shape group, a mean shape was generated from all torso surfaces within that group. Those nine torso shape groups were further categorized into three ‘curvature’ groups, based on angular measurement of the front profiles of each mean shape, as this will define the vertical curvature of a plate. Then two mean torso surfaces, a medium and a large bust shape were selected to target the prototype plate design for. Test plates were 3D printed but did not have equivalent weight as an ESAPI. Once the first plate shape was 3D printed, a design-fit evaluation-redesign cycle was initiated. A fit evaluation was performed to identify the design flaws. Then, those findings were documented and applied to the next round design, repeating this cycle four times. During each evaluation cycle, the current prototype, previous prototype versions, if applicable, and a 3D printed currently fielded plate were tested together. During the fit evaluation, the test participants’ (TPs) bra size was recorded but no measurements were taken. Based on TP’s bra size and prototype preferences, a fit table was created to correlate body size and bust shape to plate shape.The first round of fit evaluations involved the medium curvature plate and TPs (mostly with medium bust shapes). It was found that the TPs felt the top edge of the plate created pressure on the body, causing discomfort. We reduced the peak height of the prototyping plate by 20 mm to create the second iteration of the prototype. The second prototype was an improvement, however some could still feel the top edge of the plate. For the third iteration, the top and bottom plate edges were curved out to alleviate the pressure from the top edge, however, the fit test from this round indicated the curvature of the plate seems too flat. Hence the fourth prototype was developed by reducing the peak height only 10 mm from the first design with curved out edges on the top and bottom; it showed the best acceptability by all medium bust sized TPs. For future development, the accommodation envelope of the fourth iteration prototype will be evaluated so that we can delineate the anthropometric range of the central size in the target population, based on their breast size. Then, the large curvature plate will be evaluated to accommodate large breasted females (approximately 24% population according to the angular analysis of the front torso profile). Author contributions: P.L., H. C-R. and B. M. designed research plan and wrote the abstract. P.L. and H. C-R performed data analysis and fit evaluation, A.T and M.H did detail design and prototyping.