Showing papers on "Ballistic impact published in 1973"

Ballistic Impact of Textile Structures

Abstract: Previous work on transverse impact of single textile fibers is reviewed and extended to model orthogonal weaves in which fiber crossovers are simplified as pin. joints. A dynamic finite-element computer technique previously developed for single fibers is extended to model the woven panel, and this method is shown to produce results which are in sub stantial agreement with experimental observations of ballistic nylon panels. Impact of a woven textile panel is shown to exhibit substantial differences compared to the equivalent impact of a single fiber, primarily in that the propagating strain waves experience pervasive and complex interactions due to the influence of the fiber crossovers. The vast majority of ballistic energy is seen to be deposited in the orthogonal fibers passing through the impact point, while the other fibers are essentially ineffective, which suggests possible improvements in the design of textile structures intended for dynamic impact applications.

The Propagation of Adiabatic Shear

Abstract: Metallographic analysis of metals and alloys subjected to ballistic impact or explosive loading reveals thin bands that are associated with a displacement across the band. Figure 1 is a micrograph that shows examples of these bands found in SAE 4130 steel as the result of impact by a steel ball. The shear displacement is shown in this micrograph by the displacement of the surface. These bands occur in regions of general yielding and have been called adiabatic shears because there is evidence that these are inhomo-geneous zones of shear in which plastic work heats the zone adia-batically and causes thermal softening within the zone and greatly reduces the shear resistance (Ref. 1–2).

Strain-Wave Reflections During Ballistic Impact of Fabric Panels

Abstract: A numerical model is presented which describes the strain level build-up in yarns due to multiple strain wave reflections from yarn crossover intersections in a woven fabric subject to ballistic impact. Crossing yarns present barriers from which strain waves are partially reflected. The maximum yarn strain occurs at the point of impact and decays with distance along the yarn away from this point. The rapidity of decay is governed by the crossover reflection coefficient. Using observations of the deformation cone size of ballistically impacted fabric panels, it is concluded that the reflection coef ficient is small (approximately 0.01). The strain increases with time at different rates for different reflection coefficients until failure at the impact point. Extensions of this model to other fibrous structures are discussed.

Impact resistance of fiber composite blades used in aircraft turbine engines

Abstract: Resistance of advanced fiber reinforced epoxy matrix composite materials to ballistic impact was investigated as a function of impacting projectile characteristics, and composite material properties. Ballistic impact damage due to normal impacts, was classified as transverse (stress wave delamination and splitting), penetrative, or structural (gross failure). Steel projectiles were found to be gelatin ice projectiles in causing penetrative damage leading to reduced tensile strength. Gelatin and ice projectiles caused either transverse or structural damage, depending upon projectile mass and velocity. Improved composite transverse tensile strength, use of dispersed ply lay-ups, and inclusion of PRD-49-1 or S-glass fibers correlated with improved resistance of composite materials to transverse damage. In non-normal impacts against simulated blade shapes, the normal velocity component of the impact was used to correlate damage results with normal impact results. Stiffening the leading edge of simulated blade specimens led to reduced ballistic damage, while addition of a metallic leading edge provided nearly complete protection against 0.64 cm diameter steel, and 1.27 cm diameter ice and gelatin projectiles, and partial protection against 2.54 cm diameter projectiles of ice and gelatin.

Structural Properties of Dual Hardness Steel Armor

Abstract: : f a high-hardness, high-carbon frontal plate metallurgically bonded to a softer lower carbon steel backup. Since the concept of DHS used for both structural and armor purposes is new, relatively little information is available to designers on the structural properties after ballistic impact. In the present paper, four different lots of (DHS) having target hardness levels of Rc 60 for the frontal portion and Rc 50 for the backup are considered. One lot was produced by standard ausforming techniques while the other three were conventionally produced heat-treatable roll-bonded steels. Base-line mechanical property data are given. These include tensile, fatigue crack propagation, and S-N behavior. The effects of varying temperature and frequency on crack propagation rate are shown. Ballistically damaged specimens are used to provide information on residual strength and residual life.