Ballistic Limit Velocity For Continuous Fiber Polymeric Composite Materials and Polymers Through Experimental and Numerical Methods

Abstract

Composite materials are often subject to harsh operating environments which may include impact from errant projectiles of various geometries traveling at specific velocities and trajectories. Experimentalists seek to establish the ballistic limit velocity of the composite material where the composite absorbs all of the energy of the projectile traveling at an initial velocity. An analytical approach for the impact event can be difficult to reliably establish the ballistic limit of a particular composite material due to the nonlinear response including rate dependency and post-failure behavior. The finite element method has shown to be capable of modeling the impact event. However many available material models require calibration from the experimental impact tests. The goal of the present research is to develop and implement an efficient finite element simulation of the composite material under impact which does not require calibration. A general orthotropic viscoplastic material model will be presented. The viscoplastic model utilizes a more generalized form of plastic potential than previous works in that it allows plasticity to occur in the fiber direction. The model represents the nonlinear post-failure behavior through the Continuum Damage Mechanics framework by utilizing an energy balance approach. Additionally a smeared crack model algorithm is utilized to reduce the mesh dependency inherent to finite element solutions. The material model was implemented for the explicit integration solver in LS-DYNA. An implicit return mapping algorithm was utilized to integrate the material model response for each load step. The material model was validated using data from published impact testing and material characterization. The finite element simulations show that the material model is able to predict the ballistic limit velocity within a reasonable margin. Impact experiments were performed using a single-stage light gas gun. The response of standard aerospace-grade satin weave T300 carbon fiber panels using thermoplastic and thermoset matrices were compared. The ballistic limit velocities for the aforementioned composites were determined using a high speed video camera. Ballistic testing was also performed on polycarbonate panels towards the development of standardized test methods for ‘chainshot’ hazards present in the operation of the timber harvesting operations. The experimental impact results were also simulated using finite element analysis. The numerical results were compared to the experiment.