Theodore C. Carney

High-velocity impact of graphite/epoxy composite laminates

The smoothed particle hydrodynamics (SPH) technique in conjunction with the macro-homogeneous, anisotropic material concept for fiber composites has been proposed for the simulation of impact damage and penetration of composite structures. To describe material behavior under high-intensity loadings, a 3-D anisotropic elasto-plasticity constitutive model, an equation of state, and a failure criterion for unidirectional composites have been developed. Furthermore, in order to maintain material frame indifference of the constitutive equations, the polar stress rate approach was employed in the stress and strain transformations for large rotations. The above physics were incorporated into the SPH. Detailed penetration process and damage progression were simulated with graphite/epoxy laminates impacted by a steel projectile. The predicted impact response and damage patterns agree fairly well qualitatively with experimental results. This study has demonstrated that SPH can be a robust and viable analytical tool for predicting the response of fiber-reinforced composite structures subjected to high-velocity impact.

An approach for treating contact surfaces in Lagrangian cell-centered hydrodynamics

A new method is presented for modeling contact surfaces in Lagrangian cell-centered hydrodynamics (CCH). The contact method solves a multi-directional Riemann-like problem at each penetrating or touching node along the contact surface. The velocity of a penetrating or touching node and the corresponding forces are explicitly calculated using the Riemann-like nodal solver. The contact method works with material strength and allows surfaces to impact, slide, and separate. Results are presented for several test problems involving both gases and materials with strength. The new contact surface approach extends the modeling capabilities of CCH.

Reduction of dissipation in Lagrange cell-centered hydrodynamics (CCH) through corner gradient reconstruction (CGR)

This work presents an extension of a second order cell-centered hydrodynamics scheme on unstructured polyhedral cells 13 toward higher order. The goal is to reduce dissipation, especially for smooth flows. This is accomplished by multiple piecewise linear reconstructions of conserved quantities within the cell. The reconstruction is based upon gradients that are calculated at the nodes, a procedure that avoids the least-square solution of a large equation set for polynomial coefficients. Conservation and monotonicity are guaranteed by adjusting the gradients within each cell corner. Results are presented for a wide variety of test problems involving smooth and shock-dominated flows, fluids and solids, 2D and 3D configurations, as well as Lagrange, Eulerian, and ALE methods.

Modeling of Bullet Penetration in Explosively Welded Composite Armor Plate

Normal impact of high‐speed armor piercing bullet on titanium‐steel composite has been investigated using smooth particle hydrodynamics (SPH) code. The objective is to understand the effects of impact during the ballistic testing of explosively welded armor plates. These plates have significant microstructural differences within the weld region, heat‐affected zone and the base metal. The variances result in substantial ductility, hardness and strength differences, important criteria in determining the failure mode, specifically whether it occurs at the joint or within the virgin base metal. Several configurations of composite plates with different material combinations were modeled. The results were used to modify the heat treatment process of explosively welded plates, making them more likely to survive impact.

Shock-recovery experiments of sandstone under dry and water-saturated conditions

Shock-recovery experiments have been performed on Berea Sandstone under dry and water-saturated conditions using a single-stage light-gas gun. Stress levels in the range between 3.1 and 9.8 GPa were achieved by impacting projectiles in a recovery fixture. The microstructural damage of the shocked samples were analyzed with scanning electron microscopy (SEM), laser particle analysis and X-ray computed micro tomography (XCMT). The dry samples show strongly and irregularly fragmented quartz grains with an considerably reduced porosity. In contrast, the water-saturated specimens have less grain damage and higher porosity. The water in the pores distributes the stresses which reduce the contact force between the grains during the shock compression. The dynamic fragmentation of the grain-grain interactions was modeled by explicitly treating the grain-pore structure using the Smooth Particle Hydrodynamic (SPH) computational method. This is a continuum Lagrangian gridless approach that features particles.

Modeling shock recovery experiments of sandstone

We present results from mesoscale modeling of shock recovery experiments on Berea sandstone with the Smooth Particle Hydrodynamics and the Discrete Element methods. Each grain is represented with clusters of Discrete Element particles to provide explicit representation of the grain and pore structure. The grain structures simulate the structures observed using synchrotron micro tomography and Scanning Electron Microscope imaging. The modeling accounts for the influence of pore fluid and illustrates how grain/pore heterogeneity under dry and saturated states affects stress wave and grain damage behavior. The simulations show characteristics of the phenomena observed in recovery experiments. An increase in grain damage coincides with an increase in stress level and pulse duration. The grains in dry samples are extremely and irregularly fragmented with extensively reduced porosity. Less grain damage and higher porosity is observed in the saturated samples. The influence of pore fluid miti-gates the interacti...

FLAG Simulations of the Elasticity Test Problem of Gavrilyuk et al.

This report contains a description of the impact problem used to compare hypoelastic and hyperelastic material models, as described by Gavrilyuk, Favrie & Saurel. That description is used to set up hypoelastic simulations in the FLAG hydrocode.