Initial Experimental Validation of an Eulerian Method for Modeling Composites
Impact loading response of unidirectional and plain weave fiber reinforced polymer composite materials is typically modeled using a Lagrangian method such as the finite element method. However, these methods often lack a coupled equation of state. In anis
- PDF / 587,235 Bytes
- 8 Pages / 595.276 x 790.866 pts Page_size
- 36 Downloads / 213 Views
Initial Experimental Validation of an Eulerian Method for Modeling Composites Christopher S. Meyer, Christopher T. Key, Bazle Z. (Gama) Haque, and John W. Gillespie Jr. Abstract Impact loading response of unidirectional and plain weave fiber reinforced polymer composite materials is typically modeled using a Lagrangian method such as the finite element method. However, these methods often lack a coupled equation of state. In anisotropic materials, the pressure (equation of state) and deviatoric (strength) portions of the stress tensor are coupled: a shear stress can produce a volumetric response and a volumetric strain can produce a shear stress. High-velocity impacts of composite materials instigate a coupled pressure and stress response, so an equation of state is important in determining the non-uniform stress response of the material. A new composite model, which couples the pressure response to the constitutive response of the material, has been implemented in an Eulerian large deformation, strong shock wave, solid mechanics code. Experiments of steel projectiles perforating composite targets were numerically simulated to begin to validate this new composite model. This paper will discuss the coupled equation of state and strength response, and compare the results of these experiments with the results predicted by the model. Keywords Numerical simulation • Glass fiber reinforced composites • Equation of state • Multi-constituent model
14.1
Introduction
Impact of fiber reinforced polymer composites normal to the fiber direction is dominated by the fiber material properties, and impact along the fiber direction is dominated by the reinforcement material properties. For sufficiently high velocity impacts, shock waves will propagate within a composite material. Fiber materials typically have greater stiffnesses than matrix materials and so sound travels faster along fibers than in reinforcement. Likewise, impedance mismatch between constituent materials will result in reflections and refractions of these waves. Adhesive bond strength between constituent materials will also influence wave propagation and delamination. Tsai and Prakash studied weak shock wave propagation in layered media, and found that wave propagation across laminar material is strongly influenced by impedance mismatch of laminae, but also lamina thickness, wave propagation distance, and inelastic material response [1]. Behavior of laminated media may be homogenized for impacts that induce a stress wave that travels much faster than the time it takes to cross a lamina thickness [2]. Damage in fiber reinforced polymer composites consists of matrix cracking, fiber failure, and fiber/ matrix debonding, but a homogenized approach will not capture these effects, though progressive damage and failure may be considered. Also shock wave propagation in a homogenized material cannot address the differences in sound speed of the constituent materials. Under low-rate compressive loading, the thermodynamic state in pressure-volume space is akin to a stepped
Data Loading...
