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US Army and HotEnd Works explore 3D printed sintered ceramics for soldier body armor – 3ders.org (blog)

by • March 21, 2016 • No Comments

Mar 22, 2016 | By Alec

The nature of war has been changing for a long time, and yet soldiers have additional access to high end technologies than at any time preceding, it’s obvious that the manufacturing of weapons and armor needs to evolve with it. That’s why the US Army has been looking into adopting ceramic 3D printing for the redevelopment of body armor for its ground forces, that may enable additional efficient create and additional effective and speedy production. That’s why they have been collaborating with HotEnd Works on a research project, to see precisely what 3D printing can bring to a soldier’s protective gear. And while 3D printing contributes numerous production advantages, they discovered that the innovation yet needs to improve slightly to meet the high end demands needd.
The conclusions of this informative study are set out in a forthcoming study entitled “The First Static and Dynamic Analysis of 3-D Printed Sintered Ceramics for Body Armor Applications” by Tyrone Jones, Jeffrey J. Swab and Benjamin Becker, with Becker coming of HotEnd Works. That company, as you can understand, was discovereded in 2012 by Becker and Jessica Whittaker with a focus on high end material 3D printing. They are the masterminds behind the HDfab 3D printing device, that uses proprietary high density deposition innovation to 3D print high resolution ceramics with properties that manufacture it really informative for aerospace, defense, and medical applications. But they have worked and are working on different types of research projects with external partners, they are in addition planning to finalize and commercialize their 3D printing device by mid-2017.
But this latest collaboration with the US Army Research Laboratory is one of their most worthwhile projects. As they explain in their study, it is obvious that 3D printing contributes a myriad of advantages over traditional ceramics may already. “Ceramic 3-D printing contributes engineering-grade ceramic components in almost 90% less time than traditional ceramics. Typical turn around can be in days, instead of weeks, depending on the complexity of the part. This not only allows for for faster time to market, but in addition allows for for additional iterations during the create system, resulting in a advantageous end product. Additionally, 3-D printed parts can have a higher degree of complexity for mass reduction, while saving on the cost of the part for the reason of the reduction in material utilized,” they write. But the real question is: can the results compare in terms of static and quasi-static parameters, such as density, hardness, and fracture durablity, and penetration?
Figure 1: Typical Die Press Assembly

Figure 2. Representative Microstructure of AD-995 (A) and HotEnd Works Alumina (B)
To find out, the researchers tested the extent to that 3D printed ceramics stand up to the higher performance ceramics already utilized in US army body armor. Traditionally manufactured, sintered Alumina AD-995 (in addition a fewtimes called CAP3) of CoorsTek was compared to HotEnd Works’ 3D printed and sintered alumina.

Figure 3: PSD Technology
As you can understand, HotEnd Works in fact relies on an unconventional 3D printing innovation called Pressurized Spray Deposition (PSD), that involves the use of high end ceramic raw material with a one-of-a-kind polymeric binder, with the binder servicing as a temporary assist structure during part formation to accommodate overhangs and other intricate showcases. The materials are separately 3D printed of two external hoppers, and can be placed in really high precision, in patterns of 0.127mm up to 3.81mm (0.005” up to 0.150”) in diameter. That is done in a layered sequence. After formation, thermal debinding takes place over an average cycle of 24 hours, at a temperature of less than 150ºC. Thanks to this one-of-a-kind combination of materials and debinding, the resultant parts don’t need to be cleaned, but can only be transferred to a traditional electric or gas furnace to complete the densification. Afterwards, a few diamond grinding can be necessary, but not in all cases.
For the test, rod-shaped specimens of both materials were received, with really comparable properties. Both were3 mm in diameter and 50 mm long, and as can be seen in the table at a lower place, they exhibited really much like characteristics.
Table 1. Property summary

Density (g/cm3)
Flexure Strength (MPa)
Knoop Hardness – HK2 (GPa)
CoorsTek AD-995
3.92 ± 0.00
162 ± 54
13.2 ± 1.3
HotEnd Works
3.89 ± 0.08
130 ± 38
14.7 ± 1.0

So how may they stand up to a bullet? In scientific terms, are their Depth of Penetration (DOP) or residual penetration properties comparable? Experiments were set up to find out. “For DOP testing, a projectile is fired into a ceramic tile attached to a thick metal backer plate such that the projectile penetrates into the metal plate without deforming the back surface. These experiments avoid the important problem of V50 ballistic dependence on armor create (e.g., front-to-back plate ratio and material), need fewer shots than V50 tests, and have a sensitivity equivalent to that of other ballistic test methods,” they explain, with the alter in penetration into the metal plates allowing comparison.

Figure 4. Alumina Tiles preceding impact

Figure 5. Sketch of Ceramic Composite Samples.
The targets themselves were 90-mm x 90-mm ceramic tiles at a nominal thickness of 8 mm, backed by two aluminum alloy 6061 plates of 2-inch thickness, glued together with an epoxy resin. The alloy in question is a well-characterized and readily on the market backer material, and were expected to provide advantageous resolution than steel. These were shot at with 12.7-mm APM2 bullets, which include a hardened steel core penetrator, with length of 47.6 mm a diameter of 10.87 mm. For all experiments, the bullet hit the plates at 848 m/s (2782 ft/s), alyet there was a few practical variation. “The velocity was chosen in order to create a range of practical residual penetrations, while being consistent with normal operating conditions,” they explain.

Figure 6. Cross section of a 12.7-mm APM2.

(a) Front view
Figure 7. Initial conditions of ceramic composite samples in fixture.

DOP = Tb – a
Figure 8. Measurement of Residual Penetration
So how do you in fact measure penetration? Essentially, by sectioning the plates with the assist of electrical discharge machining (EDM) and manufacturing measurements with vernier calipers. Firstly, a baseline was built with the backup plates, the results of that can be seen in Table 2 at a lower place. The system was subsequently repeated for all targets. “In order to adonly for variations in the actual strike velocity, all residual penetration values were normalized to a striking velocity of 848 m/s,” they say, via an built technique for measuring penetration. The results of the six shots can be seen at a lower place.
Table 2. Ballistic Impact Measurements for Alumina Tiles

Shot #
Striking Velocity

Whilst the ceramic tiles were largely much like in properties, they did in fact find that the average DOP for the AD-995 was really a bit lower than for the 3D printed part. With correction, the DOP of the AD-995 tile was 14.43mm (with a standard deviation of 3.01mm), while it was 24.01mm (standard deviation of 2.06mm) for the 3D printed part by HotEnd Works. “In these limited experiments, the AD-995 tiles cautilized additional injure to the penetrator than the HEW Alumina tiles. The penetrator underwent two failure mechanisms, fragmentation and erosion, when it impacted the AD-995 tiles. The penetrator underwent one failure mechanism, erosion, when it impacted the HEW Alumina tiles,” they say. “The CoorsTek and HotEnd Works Alumina both started failing with tensile fracture, and so continued into comminution to dissipate the energy of the penetrator. The extent of the ceramic injure was really much like for both types of alumina,” they introduced.
Table 3. Front Photos of Reference Material

Plate 1
(Front Plate)
Plate 2




Figure 9. Penetration of 12.7mm APM2 into AA6061
To fully comprehend the results, a comparative performance value was calculated for both materials, via aluminum alloy 6061 (AA6061) plates as the reference material. Ergo, how most additional times is the plate effective than only via AA6061 plates? Through calculations, a relative comparison to of the ceramic to AA6061 is built, with the number revealing that the ceramics are that most times additional effective than AA6061 (a Cp of 5 meaning its five times as effective). The results can be seen in the table at a lower place.

Figure 10. Residual Mass of 12.7mm APM2 into AA6061

Figure 11. Residual Length of 12.7mm APM2 into AA6061

Figure 12. CoorsTek Alumina AD-995 after Impact.

Figure 13. HotEnd Works Alumina after Impact
Table 4. Comparative Performance of Ceramics Based on Cp

HotEnd Works Alumina
In short, both materials are worthwhilely additional effective than only AA6061 plates as body armor, but the 3D printed ceramics by HotEnd Works are slightly less effective than the built ceramic version. “This program was a preliminary investigation into the viability of via a 3-D printed alumina ceramic for body armor applications. The study announced that CoorsTek Alumina AD-995 yielded a lower DOP, and hence performed advantageous, than the HotEnd Works Alumina,” the researchers say. Whilst the 3D printed plates thus pretty contribute a number of manufacturing advantages, their properties can need to be improved preceding adversion. “The 3-D deposition and sintering systemes can need to be improved to provide properties that match, or exceed, those of conventionally sintered alumina,” they complete. Perhaps a fewthing for the next?

Posted in 3D Printing Application

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