DYNAMIC RESPONSE AND DAMAGE EVOLUTION OF COMPOSITE MATERIALS SUBJECTED TO UNDERWATER EXPLOSIVE LOADING: AN EXPERIMENTAL AND COMPUTATIONAL STUDY

摘要

The dynamic response and damage evolution of composite materials subjected to underwater explosive loading has been studied. The study utilizes both experimental and numerical techniques to aid in the understanding of the behavior of these materials under shock loading conditions. The objective of the project is to develop a better understanding of the response of composite materials when subjected to shock loading conditions leading to more efficiently designed structures. The focus of the work is on performing high fidelity experiments under controlled shock loading and corresponding finite element simulations of the experiments. The work is divided into three phases, each of which build and expand upon the preceding work.In the first phase of the research the transient response and development of damage mechanisms of E-Glass / Epoxy composite plates is studied. The plates are bi-axial laminates consisting of a non-woven, parallel fiber construction, and are round, flat disks. The work consists of experiments, utilizing a water filled conical shock tube and computational simulations, utilizing the commercially available LS-DYNA finite element code. Two series of experiments have been performed and simulated: (1) a reduced energy series which allowed for the use of strain gages and (2) a series with increased energy which imparted material damage. The strain data obtained from the reduced energy experiments and the corresponding simulations are correlated using the Russell Error measure, a mathematical technique which evaluates the differences in two transient data sets by quantifying the variation in magnitude and phase. It is shown that there is a high level of correlation between the experiments and the simulations when using this measure. Additionally the extent of the damage, including the individual mechanisms, from the high energy experiments and simulations are compared and show good agreement.The objective of the second phase of the project was to increase the geometrical complexity of the composite plates by shifting from flat to curved mid-sections. The plates utilized in the second part of the study are E-Glass / Vinyl Ester, 0/90 biaxial laminates. The water filled conical shock tube is utilized to impart shock loading to the plates. Computational finite element simulations are performed with the LS-DYNA finite element code. The transient response of the plates was measured using a three-dimensional (3D) Digital Image Correlation (DIC) system, which included high speed photography and specialized post processing software. This ultra high speed system records full field shape and displacement profiles in real time. The transient response of the plates is compared to the simulation results using both point-wise time histories as well as full field deformation profiles. The DIC data and the computational results show a high level of correlation using the Russell Error measure.The third phase of the project investigates the relative response of three different laminate constructions. The objective is to determine the effectiveness of the laminate variations on increasing the performance of the laminate used in the second phase. Specifically, to improve the dynamic response and mitigate the damage mechanisms that were observed in the experiments from phases one and two. Three laminate constructions have been investigated: (1) a baseline 0°/90° biaxial layup, (2) a 0°/90° biaxial layup that includes a thin glass veil between plies, and (3) a 0°/90° biaxial layup that has a coating of polyurea applied to the back face. The digital image correlation system is used to capture the real-time deformation and velocity response of the plates. The use of polyurea is shown to improve the material performance, while the inclusion of lightweight veils between the plies is shown to negatively affect the response.