Session: 03-09-02: Materials for Extreme Environments

Paper Number: 190399

190399 - Hybrid Fem-Sph Modeling of Ballistic Impact in Additively Manufactured Mechanical Metamaterials 

Lattice structures provide desirable mechanical properties and mass optimization for components that endure high-speed impacts. There have been significant research efforts in designing a variety of lattice structures for specific loading conditions, as well as a sufficient means of modeling them during extreme environments. Finite element frameworks have been used in conjunction with the Johnson-Cook constitutive model to simulate these lattice structures during ballistic impacts but tend to produce error during fracture and debris events. Smooth-particle hydrodynamics (SPH) numerical methods have been seen to improve model ballistic and high deformation impacts well through its mesh-free and particle-based method. This project aims to investigate the effectiveness of utilizing a FEM-SPH hybrid framework for modeling ballistic impacts of lattice-based structures.  To begin the investigation, an established octet-lattice structure experiment was replicated in Ansys LS-DYNA, which utilized a Johnson-Cook plasticity and failure model and Gruneisen equation of state, to capture the fracture mechanics of the octet structure during impact. This model is validated by the octet-lattice structure experiment, which consisted of a series of additively manufactured (AM) stainless steel 316L (SS316L) octet-lattice structures, varying in relative-density, that are struck by a high-speed ballistic cylinder projectile, ranging from 270-390 m/s. Key validation parameters that were reviewed included simulation convergence analysis and various key shock compression relations occurring in the structure, such as shock velocity versus particle velocity relations, elastic wave properties, displacement position profiles, and flyer speed. We further extended the simulations to spherical projectiles and examined failure phenomena commonly observed in impacted solids, including lateral cracking, spallation, adiabatic shear localization, and discing. Gaining insight into producing accurate simulations of ballistic impacts on these structures will improve our understanding of how these structures respond to these events and improve future design iterations of lattice-based structures.

Keywords: High-speed impact, ballistic impact, smooth-particle hydrodynamics, octet, lattice structures

Presenting Author: Rayan Pasha University of Kentucky

Presenting Author Biography: Rayan Pasha, is a graduate aerospace engineering researcher at the University of Kentucky specializing in structural analysis and high-speed impact modeling. His work centers on hybrid finite element method–smoothed particle hydrodynamics (FEM-SPH) simulations to study fracture mechanics and shock behavior in additively manufactured lattice structures subjected to ballistic impacts. He has developed advanced computational workflows integrating CAD, meshing software, and LS-DYNA to model complex geometries and validate simulations against experimental data.

Rayan has completed internships at NASA’s Langley Research Center and the Jet Propulsion Laboratory. At NASA Langley’s Hypersonic Airbreathing Propulsion Branch, he performed large-scale CFD simulations on a Linux-based supercomputing cluster to investigate exhaust plume interactions along hypersonic vehicle aft bodies. At JPL, he contributed to the development of a robotic lunar water sampling system intended for permanently shadowed regions of the Moon, where he designed, fabricated, and tested multi-stage actuation systems to be integrated with a water isotope tunable laser spectrometer. In addition to his internship experience, Rayan has served as Co-Project Manager of Systems and Integrations for the University of Kentucky’s rocketry club, SpaceLex, which designed, fabricated, and tested a competition rocket at IREC 2025, which reached an apogee of 10,662 feet and tested lattice structures for shock absorption in its payload.