Hemispherical Steel Projectile Research Articles

Numerical investigation of projectile impact behavior of hybrid fiber-reinforced concrete slabs

In our earlier study, the impact resistance of slabs made up of concrete containing hybrid fibers (i.e., steel and synthetic fibers in various proportions) was evaluated through an experimental program. The test specimens, measuring 600 × 600 × 90 mm, were cast with varying amounts of fibers, while some were kept as control samples without any fibers. The high-velocity impact tests were conducted using a gas-gun system, where hemispherical steel projectiles were fired at the slabs. The craters’ sizes and penetration depths were measured. The hybrid fibers in the concrete reduced spalling and scabbing damage and reduced the size of craters. In the current study, the impact response of the hybrid fiber-reinforced concrete (HFRC) slabs was investigated numerically. LS-DYNA software was employed for this investigation, and crack sizes, areas of spalling and scabbing damages, and penetration depths were estimated. The numerical simulations provided an efficient and practical tool for analyzing the HFRC slabs’ response against impact load. The use of hybrid fibers decreased front surface damage and prevented concrete particles from flying out of the back face. The inclusion of fibers in concrete increased the perforation energy by 49%–203%. The numerical predictions of penetration depth were reasonably close, with absolute errors varying from 3.6%− 32.6%, and the error in the prediction of maximum rebar strain varied from 2.5% to 12.7%. The presented model thus has the capability to predict the local damages of various types of RC and HFRC slabs with acceptable accuracy.

High-velocity impact response of titanium-based fiber metal laminates. Part I: experimental investigations

This two-part article examines the distribution of metallic layers through the thickness of fiber metal laminates (FMLs) on their response and damage when subjected to high-velocity projectile impact. Glass fiber/epoxy and Ti-6Al-4V titanium alloy sheets are used to obtain four different layups of FMLs fabricating by the hand layup process and exhibiting the same thickness of the total metal layer. Part I deals with experimental investigations of fully clamped square FMLs normally impacting at the center by hemispherical steel projectile using compressed air gun set up. Different parameters are considered to evaluate the FMLs’ performance, which includes damage degree, first cracking energy, crack length, deformation profile, and damage developed on the surface and inside the laminate. The results indicate that the highest permanent deformation and cracking are exhibited by FML 4/3-0.3, exhibiting separation of composite layers with different orientations by the metallic layer. The other FMLs exhibit lower and approximately similar permanent deformations. However, lower cracking and a relatively higher lateral delamination spread and opening of the interlayer are exhibited by FML 2/1-0.6 in which composite layers are arranged together than FML 4/3-0.3, signifying that the damage spreading laterally can be reduced by dispensing titanium layers. The ballistic resistance is found to be similar for FMLs. The levels of permanent deformation, cracking, and delamination with their opening and spreading are lesser for titanium-based FMLs than aluminium-based FMLs. The ballistic response of FMLs will be evaluated using analytical modeling in an accompanying study (Part II).

Experimental and numerical studies on the ballistic impact response of titanium sandwich panels with different facesheets thickness ratios

The ballistic limit velocity, energy absorption and the effects of facesheets thickness ratios for three types of sandwich panels consist of titanium facesheet and aluminum honeycomb core were studied experimentally and numerically. The tests are carried out by a nitrogen gas gun and 24 g hemispherical steel projectiles with velocity ranges from 100 m/s to 190 m/s. A proper ABAQUS/Explicit model was developed using the experimental data. Results shown the impact energy mainly absorbed by the rear facesheet in symmetrical sandwich panels. The ballistic limit enhanced almost linearly with increasing rear or front facesheet thickness in specimens with the same weight.