In Part I of our 2025 PASS review, we covered Canadian work on flexible rifle plates, a plate sizing optimization study, and Dutch cooling vest research. These are topics of general interest which might give readers some indication of where research into finished armor systems is heading. This installment, the second of four, covers three presentations from Bruges which address questions ranging from manufacturing fundamentals to threat characterization – research with direct implications for how armor is made, tested, and specified.
Consolidation Pressure: Quantifying a Key Manufacturing Variable
Avient Protection Solutions, working with Fraunhofer EMI, presented research that should be required reading for anyone manufacturing or specifying UHMWPE armor. Their presentation examined how consolidation pressure during hot-pressing affects ballistic performance against AK47 MSC projectiles.
The materials tested were Dyneema HB212, HB210, HB311, and HB480, pressed at 20, 165, and 300 bar. (2 MPa, 16.5 MPa, and 30 MPa, respectively.) The results establish a clear hierarchy: Higher consolidation pressure means a higher V50, decreased depth of penetration, and increased projectile core deformation.
But here’s the critical finding: The improvement isn’t linear. The jump from 20 to 165 bar produced dramatic improvements across all metrics. Going from 165 to 300 bar? The gains were exceedingly modest. This suggests there’s a threshold effect at play; below a certain pressure, you’re leaving significant performance on the table, but, beyond a certain point, additional pressure yields little-to-no further return.
The mechanism appears to be porosity reduction. Shock property measurements using planar plate impact showed systematically lower shock velocities in panels pressed at 20 bar compared to 165 bar, particularly below particle velocities of 1100 m/s. The researchers attribute this to residual porosity in the low-pressure panels. Higher shock velocities mean higher contact pressures on the projectile, more core deformation, and ultimately better ballistic resistance.
Another finding, very useful for quality control and the characterization of R&D test panels, is that the team developed a statistical relationship that can predict V50 from depth-of-penetration measurements at a single reference velocity well below V50. This means manufacturers could potentially screen panel quality quickly, without shooting a large number of panels to destruction. The correlation held remarkably well across all four UHMWPE types and all three consolidation pressures.
For armor manufacturers, the message couldn’t be any clearer or simpler. If you’re pressing below 165 bar, you’re probably not getting the performance your material is capable of delivering.
I’d also note that prior work has been done on this question, and it generally agrees with that conclusion, with most finding diminishing returns past 200 bar consolidation pressure, and in some instances even reduced performance at higher pressures than that.
Effect of consolidation pressure on the impact behaviour of AK47 MSC on UHMWPE composite panels
H. van der Werff1, U. Heisserer1, J. van Elburg1, W. Riedel2
1Avient Protective Materials (APM), P.O. Box 1163, 6160 BD Geleen, The Netherlands, [email protected]
2Fraunhofer Institute for High Speed Dynamics, Ernst-Mach-Institute (EMI), Zermelo Str. 4, D79104, Freiburg, Germany.
Body Habitus and Armor Fit
A JHU/APL study addressed something the armor testing community has largely ignored: How does the wearer’s body type affect BABT outcomes?
The research used a clever experimental design. Instead of full post-mortem human surrogate (PMHS) testing with all its biological variability, they isolated the variables of interest – air gap between armor and body, and flesh thickness at the impact point – using excised tissue samples positioned over load cells and clay blocks. This allowed them to systematically vary these parameters while keeping everything else constant.
The findings confirm what intuition suggests but quantifies it precisely: Both air gap and flesh thickness are protective factors. For every millimeter of air gap or tissue thickness, clay BFS decreased by approximately 1mm. Force measurements followed a decaying exponential relationship with these parameters.
When they applied these relationships to PMHS test data from previous studies, the adjusted metrics proved to be better predictors of injury outcomes than impact velocity alone. The fit metrics all improved substantially when body habitus was factored in.
The implications for armor testing standards are significant. Current clay-backed testing with the armor pressed directly against the backing material represents a worst-case scenario that doesn’t reflect operational wear conditions. Real armor on real people has standoff – sometimes significant standoff, depending on body type, carrier type, and armor fit. An armor design optimized purely for the clay test might not be optimal for actual wearers.
For individual users, the takeaway is more nuanced. If you’re lean with minimal soft tissue coverage over your ribs, the protective benefit of that tissue isn’t there. Armor fit and trauma-reduction layers may become more critical. Conversely, if you’re carrying more mass in the torso, you have some built-in padding that the clay test doesn’t capture.
The Effects of Armour Fit and Body Habitus on Behind Armour Blunt Trauma Loading
A. Iwaskiw1, K. Ott1, N. Hahne1, M. Vignos1, N. Steiner1, R. Hingorani1, M. Clark2 1The Johns Hopkins University Applied Physics Laboratory (JHU/APL), 11100 Johns Hopkins Road, Laurel, MD 20723, [email protected] 2 U.S. Special Operations Command, 10 General Greene Avenue, Natick, MA 01760
Ceramic Geometry, Shot Location, and Performance – Hexagons vs. Squares Against 7.62×39mm AP
The Indian Institute of Technology Delhi presented a study examining something surprisingly understudied: Does the shape of ceramic tiles in mosaic armor systems affect ballistic performance, and where exactly are these systems most vulnerable?
Using 6.5mm thick hot-pressed B4C tiles in both hexagonal (17mm edge, 30mm edge-to-edge) and quadrilateral (25mm square) configurations, they conducted high-velocity impact tests with 7.62×39mm hardened steel core projectiles. The tiles were bonded to either aluminum or polycarbonate backing blocks, and impacts were targeted at tile centers, edges between two tiles, and vertices where three tiles meet.
The backing material turned out to be more influential than expected. With 150mm thick aluminum backing, the stiffness was so high that projectile dwell time on the ceramic increased dramatically – to the point where there was essentially no measurable depth of penetration. The cores were completely eroded and fragmented after their interaction with the ceramic, and there was no meaningful penetration into the aluminum backer. When they reduced the aluminum backing to 75mm, they finally got measurable DoP values, but they were still quite low. The polycarbonate backing, being more compliant, allowed for better differentiation between test conditions.
The key finding on tile geometry is that it’s effectively a wash. DoP values between hexagonal and quadrilateral tiles weren’t dramatically different in this preliminary work. Residual core length showed slight differences: Hexagonal tiles consistently produced shorter residual cores than quadrilateral tiles, possibly hinting at better projectile erosion. As expected, impacts at tile vertices produced higher DoP and longer residual cores than impacts at edges. The vertex – where three tiles meet in a quadrilateral array or six tiles meet in a hexagonal array – is the weak point.
This has interesting implications for mosaic armor design. First, “tile geometry” in isolation is a second-order lever. The first-order performance drivers are seam width, adhesive stiffness/thickness, confinement, vertex density, and whether you allow 4-way vertices. The current work points to adhesive and gap width as known factors via prior work they cite, and they themselves kept adhesive thickness minimal and added a top confinement tape to reduce ejecta.
Second, if vertices are weak, treat them like design objects. You can (a) eliminate 4-way corners (offset patterns), (b) reduce vertex density (bigger tiles, at multi-hit cost), (c) “cap” vertices with deliberate inserts or local overwrap, or (d) make the vertex region mechanically closer to “edge,” for example by using interlocking/scarf joints.
Third, for the specific tile sizing in the paper, hex tiles are likely the better default, but square can be the better manufacturing choice if you commit to an offset/anti-vertex layout. A “masonry-style” square grid would have a lower vertex density than a hexagonal tiling. The worst option is square tiles in a perfect grid with 4-way corners.
Effect of Personal Body Armor’s Ceramic Geometry and Shot Location in Defeating 7.62 mm Hardened Projectiles
Kartikeya Kartikeya1, Mohit Garg1, Hemant Chouhan1, Makhan Singh1 and Naresh Bhatnagar1
1Department of Mechanical Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi – 110016, India
[email protected]
