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2020 Research Highlight: Multi-scale Finite Element Modeling of Ballistic Impact Damage in a Woven Composite

Multi-scale Finite Element Modeling of Ballistic Impact Damage in a Woven Composite

Mr. Christopher S. Meyer
CCDC Army Research Laboratory,
University of Delaware
Dr. Bazle Z. (Gama) Haque
University of Delaware
Prof. John W. Gillespie, Jr.
University of Delaware
Dr. Daniel J O’Brien
CCDC Army Research Laboratory

High velocity impact on a plain weave composite target causes damage across multiple length scales. Macroscale transverse deformation wave and stress wave propagation lead to mesoscale fracture within and between interwoven fiber tows, called transverse cracking (TC) and tow-tow delamination (TTD) cracking respectively. Mesoscale fracture is composed of rate-dependent microscale fiber-matrix interface debonding and matrix plasticity and fracture. Further, atomic scale mechanisms govern these microscale behaviors. A multiscale modeling approach incorporating input from lower length scale models into a meso-mechanical finite element model (FEM), which includes mesoscale progressive damage and failure, enables prediction of the ballistic limit (V_BL) of macroscale composite targets.

The phenomenological cohesive zone model (CZM) is used to model TCs and TTD cracks in continuum fiber-matrix composite tows with cohesive zones placed across and between tows based on experimental observations. These continuum tows are woven together into a meso-mechanical FEM subjected to ballistic impact. CZMs use traction-separation laws (TSL) to describe the energy of fracture by relating the tractions inhibiting fracture as a function of the separation distance between incipient fracture surfaces. Micro-mechanical FEMs are being developed to predict mixed-mode TSLs for meso-mechanical models. Micro-mechanical models include rate-dependent matrix plasticity and fiber-matrix interface debonding from experimental data and lower length scale modeling. These models are used to compute the energy per unit area of fracture from which the TSLs are derived.

Continuum FEMs without resolved meso-architecture do not adequately predict V_BL. Incorporating mesoscale woven tows and matrix improves V_BL prediction. Including mesoscale damage mechanisms such as TTD cracks further improves V_BL prediction. This accurate prediction of V_BL enables the materials-by-design approach to improving ballistic performance in composite targets by incorporating lower length scale material behavior and mechanics into ballistic impact scale models.