Extreme Energy Absorption in Thin-Film and Mat Materials under Ultra-High-Rate Micro-Projectile Impact

Lightweight materials that absorb large kinetic energy per unit mass are critical for protective structures, yet their behavior at ultra-high strain rates (10⁶–10⁸ s⁻¹) is poorly understood. We use laser-induced projectile impact testing (LIPIT), launching a silica microsphere at 300–900 m/s into freestanding targets, to study three nanostructured thin-film systems and identify features governing extreme-rate energy dissipation.

Freestanding polystyrene (PS) films, normally brittle at room temperature, undergo extensive crazing and adiabatic self-heating above Tg, producing melt-like flow and record energy absorption that increases as thickness decreases. Absorption collapses for low-molecular-weight, poorly entangled PS, confirming entanglement enables craze-mediated melt draw.

Polystyrene-grafted silica and Fe₃O₄ nanoparticle (PGN) films add a nanoparticle network atop chain entanglement. Well-entangled PGNs show the same melt-draw mechanism as linear PS but reach even higher absorption, tracking chains anchored per particle, while poorly entangled PGNs behave brittlely. Thinner films develop more uniform heating on impact, favoring the melt draw behind this thickness effect.

Finally, isotropic multiwall carbon nanotube (MWCNT) mats, despite modest quasi-static strength, reach energy absorption far higher than Kevlar or Dyneema. Dissipation arises not from melt flow but from mat densification, frictional sliding of load-bearing tubes, fibril formation, and fracture of the drawn fibrils.

Together, these systems show fragile or compliant materials can achieve exceptional micro-ballistic energy absorption when their architecture permits large-volume, rate-activated reconfiguration — via entanglement-enabled crazing, nanoparticle network coupling, or nanotube sliding.