Controlled blast studies found that standard unisex armor reduced peak pressures for both male and female mannequins, but larger air gaps around the female torso increased impact exposure, raising new questions about how well current armor fits and protects different body types.
Research: Gender-based effects of impact energy exposure in combatants. Image credit: Svitlana Hulko / Shutterstock
In a recent study published in the journal scientific reportresearchers investigated the performance of standard body armor under blast conditions on male and female combatants. Armor reduced both peak pressures, but significant differences emerged between the sexes. The female body shape created a large air gap between the armor and torso, increasing energy entrapment and greater exposure to impact.
These findings raise concerns about how well unisex armor protects different body types from blast exposure under controlled blast conditions, with potential implications for blast exposure and injury risk. Explosive orientation further influenced the results, highlighting the potential limitations of current unisex armor designs.
Bulletproof vests have long been designed around men’s torsos, but today women are increasingly finding themselves on the battlefield. Many female combatants still rely on unisex armor that scales down male designs, often resulting in a poorer fit in the chest, waist, and upper body.
This can reduce coverage and shift during movement, causing discomfort and difficulty breathing. Additionally, air gaps may occur between the armor and the fuselage, which may alter pressure transfer during blast exposure.
These issues may reduce the effectiveness of protection for some female personnel. However, the impact of gender-based anatomical differences on the fit and performance of armor remains unclear.
Blast armor research design and air gap testing
In this study, researchers used a controlled experimental setting to examine differences in blast exposure and armor performance between female and male combatants. They tested anatomically representative female and male mannequins fitted with commercially available small arm protection inserts (SAPI) plates. The mannequins included realistic features such as silicone skin, rib structure, and breast anatomy on the female models. To capture pressure changes, sensor arrays were placed at key locations on the torso, including the sternum, nipples, and underbust.
To assess the suitability of the armor, the team used heat-shrinkable plastic and gap-filling foam to measure the air gap between the armor and the fuselage, allowing them to accurately map the thickness of the gap. Both mannequins were then exposed to a controlled blast wave in an open field setting generated by a Composition C4 charge placed 2 meters apart. To assess the direction of the explosion, the researchers oriented the mannequin at angles ranging from 0° to 180° from the point of explosion.
The researchers repeated each condition three times in both armored and unarmored conditions. They recorded pressure data using a data acquisition system. High-speed video recording using background-oriented Schlieren (BOS) technology captured the behavior of the shock wave and its interaction with the protection plate.
The research team analyzed pressure waveforms, impulses, and energy distribution across different regions of the body. They also investigated the role of air gaps, armor fit, and body shape in influencing pressure transfer and energy trapping during blast exposure.
Gender differences in blast pressure and impact force
This study revealed clear gender-based differences in how body armor affects exposure to explosions. The armor reduced peak pressure for both mannequins, but increased shock, especially for the female mannequin tested here. Female mannequins showed an up to 79% increase in total impulse compared to unarmored, with consistently higher impulses in the underbust region, although findings in the bust region were more mixed. These effects were associated with larger air gaps, which reached up to 2.97 cm in women compared to 1.59 cm in men, allowing energy to be trapped and exposure to pressure to be prolonged.
The direction of the blast also played an important role. Frontal (0°) exposure produced the highest peak pressures (111 kPa for men and 108 kPa for women) and shocks, with mean shock values up to 73% higher than at oblique angles. Although peak pressures were similar between men and women, women consistently experienced greater urges due to differences in armor fit and body shape. In contrast, males showed higher peak pressures in some areas, likely due to closer contact of the armor.
High-speed imaging further demonstrated that the shock waves reflected and diffracted around the edges of the armor, creating complex energy patterns. In women, breast anatomy altered the position of the plate, increasing the angle by 3.1°, creating a larger air gap and increasing energy trapping. These dynamics resulted in multiple pressure peaks and extended exposure periods. Taken together, these findings suggest that while current armor reduces peak pressures, poor fit for female combatants may increase overall energy transfer and increase the risk of blast injury.
What comprehensive body armor design means
This study highlights important gender differences in blast protection and shows that unisex body armor may not provide the same pressure and impact distribution for different female and male torso shapes. This finding highlights the need for more comprehensive design strategies. Armor designers and manufacturers need to move beyond scaled male models and develop fit-specific solutions that take into account female anatomy, potentially lowering peak pressure levels and overall energy transfer.
Going forward, testing strategies should incorporate a variety of body types and realistic fit conditions to better understand changes in protection. However, the results are based on a single male and female model, which limits their generalizability. Future studies should target a wider range of body types, including differences in breast size, to better understand how anatomical differences affect armor performance. This could support the development of more effective and customized protection systems.
