Researchers atSan Diego State University’s (SDSU)Experimental Mechanics LaboratoryandAdvanced Manufacturing Hubhave developed 3D printed continuous carbon fiber “meta-skins” designed to improve impact mitigation in composite foam-core structures. Published inAdditive Manufacturing Letters, the study by Sean Eckstein, Sophia Benkirane, and George Youssef evaluates pseudo-woven composite skins fabricated using automated tow placement (ATP) and compares monocoque and sandwich configurations under low- and moderate-velocity impact. The results show that optimal performance depends on impact regime, with single-skin structures performing better at lower speeds and two-skin sandwich designs providing improved mitigation at higher velocities.
Pseudo-woven architecture via automated tow placement
The study reports the fabrication of continuous carbon fiber composite skins using a robotic ATP system. Rather than producing a conventional cross-ply laminate, the researchers created a pseudo-woven structure composed of alternating 0° and 90° tow sublayers. The interlaced architecture aims to improve load distribution and delamination resistance compared to traditional cross-ply laminates. Each successive sublayer was shifted laterally by 6 mm, forming an interwoven pattern through the laminate thickness.
Up to 40 sublayers were stacked to produce 2 mm-thick meta-skins. These skins were bonded to cylindrical polyurea foam pucks in two configurations. In the monocoque design, a single meta-skin capped the foam core. In the sandwich configuration, the foam was enclosed between two meta-skins. The objective was to evaluate how structural configuration and skin architecture influence dynamic impact response.
Low-velocity testing favors monocoque design
Low-velocity impact experiments were carried out with a drop tower system. A 2.7 kg hemispherical impactor hit the specimens at 4.43 m/s. High-speed imaging and digital image correlation (DIC) tracked full-field strain and deformation during impact.
Under these conditions, the monocoque configuration exhibited lower peak force and longer impact duration than the sandwich structure. The single-skin design produced a lower peak force and a longer impact duration, suggesting more spread-out energy absorption. The researchers link this to greater foam involvement, which lets the material deform within its hyper-viscoelastic plateau region. The monocoque samples absorbed nearly 100% of the impact energy and outperformed cross-ply benchmarks by approximately 15%, despite having a lower fiber volume fraction (29 vol.% versus 48 vol.%).
Force–time histories, strain distributions, and quantitative metrics including impulse and absorbed energy showed that the absence of a bottom skin enabled greater foam compression and energy dissipation at lower impact speeds.
Sandwich configuration performs better at higher velocity
To assess higher strain-rate behavior, the team conducted moderate-velocity impact tests at 15 m/s using a small-scale shock tube to accelerate a projectile.
Source: 3D Printing Industry
