1. Design of flexible torso armor based on biomimetic models
for non-assembly 3D printing
Kelly Mellarkey
Mentored by Dr. Shane Bartus
Introduction
Materials and Methods (continued)
Results (continued)
In 2012, the US Army opened 14,000 positions to women, including combat roles, necessitating body armor for women. A major problem with issuing everyone the traditional rigid body armor is the fit for female soldiers. Flexibility and range of motion are also issues for both men and women with the monolithic design currently in use. According to the Anthropology and Human Factors Teams at the Natick Soldier Research, Development and Engineering Center, this kind of improper fit leads to a decrease in the performance of the soldiers, costing lives (Reinert, 2014).
Biomimicry incorporates elements of nature into human problems. The purpose of this investigation was to design torso armor based on biomimetic systems that would provide greater flexibility than the armor currently in use. Recent advancements in 3D printing would allow the manufacture of complicated geometries without requiring any assembly of the individual plates. The intent is to fit female body forms better, as well as to provide greater flexibility and improve soldier survivability.
The vertical portion was curved forward and backward and the angle at which each of the vertical connectors was bent were measured within the program. The horizontal portion was curved outward, as in Figure 5, and inward and the same measurements were taken of the horizontal supports.
The average angles for each of these Directions of Curvature (DOC) were calculated and graphed in Figure 4.
The traditionally used SAPI plate, as a single rigid piece, automatically has a value of zero degrees for all of the flexibility
measurements taken on the new design. The results of the new design are significantly higher than this, all within a range of approximately 16 to 59 degrees for each of the individual connectors across all four DOC.
Both of the vertical DOC are important in the movement of a soldier, and the outward horizontal one is essential for conforming to the body. The inward horizontal DOC does not necessitate much flexibility, fitting with the data that indicates it being the least flexible of all four.
5 cm
2 cm
Figure 5: The outward-curved horizontal analysis portion at full curvature. The measurements of the connector angles make up the fourth plot of Figure 4
Figure 3 (right): All four plates arranged into a full armor assembly
Figure 2 (left): Detail of the three-socket connector and horizontal support of the mesh backing
10 cm
Materials and Methods
Results
Conclusions
A preliminary design was created in the Computer-Aided Design (CAD) program SolidWorks 2014®. The shape and pattern were bio-inspired from the scales of the arapaima, the South American armored fish shown in Figure 1. The scale construction of the arapaima allows it to withstand attacks from piranhas while maintaining a high degree of mobility.
A flexible mesh backing, which can be seen in Figure 2, was created to link with the scales. This design was carried out to the completion of a front, a back, and two side plates, displayed in Figure 3. The front plate deviated from a traditional Small Arms Protective Insert (SAPI) plate in that it included extra scales for increased coverage. The shape of the side plates differed from SAPI side plates in order to correspond with this.
After this design was finalized, analysis of its flexibility was carried out on two separate portions of it. The first consisted of three of the main type of scale stacked vertically and the second consisted of three stacked horizontally. The two portions of the armor were tested for range of motion using the Physical Dynamics tool within SolidWorks 2014®, which keeps real-world properties and relations intact when moving an assembly.
The goal of this investigation was to design a bio-inspired torso armor that is more flexible than the type currently being used in the military and is able to be 3D printed with no assembly required.
The scale design successfully resembles that of the arapaima fish, with each scale attaching at a single point to the flexible mesh backing, similar to the scales of the fish each attaching at a single point to its flexible skin. The data extracted from it supports the existence of its improved flexibility over the conventional SAPI plate. The fully interlocking components of each plate allow them to be printed in one piece, as well.
Since the design was never 3D printed, an extension of this investigation may include printing and examining a thermoplastic model. A long-term objective would then be for an optimized design to be printed in armor-grade ceramics and its ballistic protection factor tested.
References
Reinert, B. (2014, October 9). Natick studies link between body armor fit, performance. Retrieved from between_body_armor_fit__performance/
Stewart, D. J. (2012). Arapaima sp. from Guyana [Online image]. Retrieved May 6, 2015 from
100 cm
Figure 1: The arapaima fish and its armor-like scales (Stewart, 2012)
Figure 4: Displays the range and quartiles of the maximum angle of each connector for the forward-, backward-, inward-, and outward-curved three-scale portions.