Defense

Ballistic Performance of Multilayer Graphene

The micro-ballistic experiment. (A) Scheme of the experiment. (B) Side-view image of a moving m-bullet taken by triple exposure at time steps t₁-t₃. (C) MLG membrane on a sample holder after ?-LIPIT. Impact regions are highlighted by green backlight. (D) A schematic illustration of penetration steps. (i) Pre-penetration stage; (ii) Conic deformation stage; (iii) Fracture stage; (iv) Post-penetration stage showing the film morphology after penetration and relaxation. Scale bars, 50 µm.

[1] J.-H. Lee, P.E. Loya, J. Lou, E.L. Thomas, “Dynamic mechanical behavior of multilayer graphene via supersonic projectile penetration” Science 346, 1092 (2014).

 

Polymer Nanocomposites

Macroscopic ballistic impact test. (a) Photograph of a polyurethane armor disc (Cleargard^®, Courtesy of BAE Systems) impacted by copper jacketed 9 mm lead projectiles. (b) Magnified view of the projectile and penetration path. The scale bar is 5 mm. (c) Schematic of the nanostructure of a polyurethane nanocomposite comprised of glassy and rubbery domains.

Cross sectional SEM images of the horizontally-oriented lamellae targets for three velocities as indicated. (a)-(c) False color maps of lamellar spacing on a logarithmic scale. (d)-(f) False color maps of angular deviation from the original orientation on a linear scale. All scale bars are 1 ?m.

[1] J.-H. Lee, D. Veysset, J. Singer, M. Retsch, G. Saini, T. Pezeril, K.A. Nelson, E.L. Thomas, “High strain rate deformation of layered nanocomposites” Nature Communications 3, 1164 (2012)

Enhancement of Plastic Deformation using Nano-scale Frames for Future Armors

(a) Schematic illustration of the microscopic uniaxial compression experiment. SEM images of (b) polymer nanoframe (PnF), (c) carbon nanoframe (CnF), and (d) carbon-polymer nanoframe (CPnF) pillars. (e?g) SEM images after uniaxial compression tests.

Outstanding energy absorption per unit weight (or specific energy absorption (SEA) has been demonstrated.

[1] J.-H. Lee, L. Wang, M.C. Boyce, E.L. Thomas, “Periodic bicontinuous composites for high specific energy absorption” Nano Letters 12, 4392 (2012).

[2] J.-H. Lee, L. Wang, S. Kooi, M.C. Boyce, E.L. Thomas,“Enhanced energy dissipation in periodic epoxy nanoframes” Nano Letter 10, 2593 (2010).