Title

Progressive damage and delamination in composite plates under dynamic loading: Analytical modeling and experimental validation

Date of Completion

January 2008

Keywords

Engineering, Civil|Engineering, Mechanical|Engineering, Materials Science

Degree

Ph.D.

Abstract

A general methodology for determining and tracking progressive damage in woven fabric laminated composite plates subjected to dynamic loads has been developed and experimentally validated. The progressive damage theory is based on three-dimensional rate-dependent elasticity and nonlinear anisotropic plasticity which utilizes distinct in-plane and transverse failure criteria and post failure behavior. Delamination is accounted for using two different methods (shear degradation and cohesive layer modeling) and the relative merits of these two approaches are evaluated. The progressive damage theory and delamination modeling capability are implemented in a commercial finite element (FE) code and used to perform validation simulations.^ Results from off-axis tension tests at different loading rates were used to determine the in-plane material properties for the progressive damage theory. FE simulations of the off-axis tension tests demonstrate that the theory is able to reproduce the observed test results very well over two orders of magnitude of strain rate and at high strains (up to 15%). This includes tracking of the nonlinear stress-strain behavior, prediction of failure load and prediction of the failure mechanism.^ Results from short beam shear tests are used to determine the transverse material properties for the progressive damage theory and to provide experimental validation of the three-dimensional theory with delamination modeling included. A novel method to determine transverse shear properties based on a 0° short beam shear test is developed and used. Simulations of additional off-axis short beam shear tests with delamination modeling are performed and compared to experimental results for validation. Excellent agreement between the test and simulation results is obtained.^ Additional validation of the progressive damage theory with delamination modeling was conducted using transversely loaded thick composite disk specimens. The loading rate was adjusted to impact the disks to produce strain rates from quasi static levels to 200 s-1. Simulations of the impact event using both implicit and explicit time integration methods were performed and compared with experimental results. Results indicate that the loads, strains, strain rates, and failure limits and locations are accurately simulated using the progressive damage theory. ^