Ballistic Strength Research Articles

Structural Repair of Composite Structural Armor

Composite structural armor (CSA) is a multifunctional material that provides ballistic protection, stiffness, and strength at minimum weight. It consists of a multilayered architecture of polymer composites, rubber and ceramic tiles, stacked in a precise manner to obtain optimal performance. During its lifetime, CSA will experience manufacturing defects and be subjected from low to high velocity impact threats that will reduce the performance of the structure. The ability to repair a CSA is consequently an important factor in the future deployment of the CSA. The present study addresses the problem of the repair of CSA in a minimum number of steps. Several potential repair methods are introduced, and an adhesively bonded plug repair scheme is then further analyzed. Virgin (control) and repaired CSA beams are manufactured and their static behaviors are compared in a four-point bend test. The performance of a scarf patch repair is assessed. The effect of three scarf angles and two repair adhesive systems, one being low-temperature cure and the other room-temperature cure, are compared. The room-temperature cure repair system offers only a limited ability to bond to the different material layers, thereby limiting the performance of the repaired CSA. On the other hand, it is found that the low-temperature cure repair system provides sufficient interfacial strength to allow the repair to recover an appreciable amount of the original structural performance of the beams. Furthermore, it is found that the repair efficiency increases as the scarf angle decreases. This study clearly demonstrates that it is possible to repair the through-thickness section of CSA, in a single-step operation, and renew structural performance.

Mechanical Behavior of Intercalated Polycarbonate Layered-Silicate Nanocomposites

AbstractThe effect of layered-silicates on the mechanical response of intercalated polycarbonate (PC) nanocomposites subjected to quasi-static tensile, compressive and ballistic impact testing conditions has been investigated. These nanocomposites were melt-processed, in which good dispersion of nanoclays and adequate adhesive bonding between the nanoclay and PC matrix are achieved. However, their ductility upon tensile loading is significantly affected; a transition from ductile to brittle deformation occurs at clay loading of about 3 wt.%. Stress whitening is evident in the tensile- and ballistic-tested 1.5, 2.5, and 3.5 wt.% clay nanocomposites, and is attributed to the light scattering by microvoids, which are presumably formed from either crazing of PC or debonding of the nanoclay tactoids upon mechanical deformation. The effect of clay loading on the ballistic impact strength of the monolithic PC nanocomposites and layered PC/PC-nano/PC composites is determined. Compressive yield strength measurements are obtained at strain rate of 0.001/s for the monolithic PC nanocomposites and are utilized to correlate with the ballistic impact strength of the layered PC/PC-nano/PC composites. Thermal degradation is noted in these PC nanocomposites, and its effect on the mechanical deformation is briefly discussed.

Commercial applications of ion beam deposited diamond-like carbon (DLC) coatings

We report the results of applications development by Diamonex on ion beam deposited diamond-like carbon (DLC) coatings. Many of the process scale-up issues for ion beam deposition of DLC coatings have been solved. Commercial applications for abrasion resistant DLC-coated optics take advantage of the transparency, chemical inertness, low friction coefficient, high hardness and excellent adhesion of ion beam deposited DLC coatings. DLC-coated polycarbonate sunglass lenses are more resistant to abrasion by #0000 steel wool than any polycarbonate sunglasses commercially available. Using DLC, highly durable coatings with a variety of iridescent reflected colors can be produced. In addition to providing polycarbonate with substantially improved abrasion and chemical resistance, the ballistic strength of polycarbonate is maintained. DLC-coated float glass windows in supermarket laser bar code scanners demonstrated a projected average lifetime of 9 years, approximately 100 times longer than uncoated glass. ZnS and ZnSe IR windows coated with DLC coatings 1–2 μm thick are highly transparent from 3 to 15 μm wavelength and exhibit large improvements in chemical resistance and abrasion resistance relative to uncoated ZnSe and ZnS. The combination of the high electrical resistivity, relatively high thermal conductivity, low friction coefficient, high hardness and excellent adhesion to metals of ion beam deposited DLC, permits its use as a scratch-resistant dielectric layer for copper heat removal devices in multichip modules.