Date of Award

2011

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

First Advisor

Arun Shukla

Abstract

An analytical and experimental study has been conducted to investigate the blast resistance and mitigation behaviors of structural materials. Understanding the failure mechanisms in these materials will lead to an optimal design of light weight structures capable of withstanding blast loadings. This improved blast mitigation property is extremely important in protecting many commercial, naval, aerospace and defense structures.

A controlled study has been performed to understand fracture and damage in glass panels subjected to air blast. A shock tube apparatus has been utilized to obtain the controlled blast loading. Five different panels, namely plain glass, sandwiched glass, wired glass, tempered glass and sandwiched glass with film on both the faces are used in the experiments. Fully clamped boundary conditions are applied to replicate the actual loading conditions in windows. Real-time measurements of the pressure pulses affecting the panels are recorded. A post-mortem study of the specimens was also performed to evaluate the effectiveness of the materials to withstand these shock loads. The real time full-field in-plane strain and out-of-plane deformation data on the back face of the glass panel is obtained using 3D Digital Image Correlation (DIC) technique. The experimental results show that the sandwich glass with two layers of glass joined with a Polyvinyl butyral (PVB) interlayer and protective film on both the front and back face maintains structural integrity and out performs the .other four types of glass tested.

Experimental and numerical studies were conducted to understand the effect of plate curvature on blast response of aluminum panels. A shock tube apparatus was utilized to impart controlled shock loading to aluminum 2024-T3 panels having three different radii of curvatures: infinity (panel A), 304.8 mm (panel B), and 111.76 mm (panel C). Panels with dimensions of 203.2 mm x 203.2 mm x 2 mm were held with , mixed boundary conditions before applying the shock loading. A 3D Digital Image Correlation (DIC) technique coupled with high speed photography was used to obtain out-of-plane deflection and velocity, as well as in-plane strain on the back face of the panels. Macroscopic postmortem analysis was performed to compare the yielding and plastic deformation in the three panels. The results showed that panel C had the least plastic deformation and yielding as compared to the other panels. A dynamic computational simulation that incorporates the fluid-structure interaction was also conducted to evaluate the panel response. The computational study utilized the Dynamic System Mechanics Analysis Simulation (DYSMAS) software. The model consisted of the shock tube wall, the aluminum plate, and the air (both internal and external) to the tube walls. The numerical results were compared to the experimental data. The comparison between the experimental results and the numerical simulation showed a high level of correlation using the Russell error measure.

Experimental studies were conducted to understand the effect of plate curvature on the blast response of 32 layered carbon fiber epoxy panels. A shock tube apparatus was utilized to impart controlled shock loading on carbon fiber panels having three different radii of curvatures; infinite (panel A), 305 mm (panel B), and 112 mm (panel C). These panels with dimensions of 203 mm x 203 mm x 2 mm were held under clamped boundary conditions during the shock loading. A 3D Digital Image Correlation (DIC) technique coupled with high speed photography was used to obtain out-of-plane deflection and velocity, as well as in-plane strain on the back face of the panels. There were two types of failure mechanism observed in all the three panels: ( fiber breakage and inter-layer delamination. The fiber breakage was induced from on the face exposed to the shock loading (front face) and continued to the interior. Delamination occurred on the side of the specimen as well as on the front face. Macroscopic postmortem analysis and DIC results showed that panel C can mitigate higher intensity (pressure) shock waves without initiation of catastrophic damage in the panel. Panel B could sustain the least shock wave intensity and exhibited catastrophic failure. Panel A exhibited intermediate blast mitigation capacity.

Experimental studies were conducted to understand the effect of varying plate thickness on the blast response of doubly curved E-glass/vinyl Ester panels. A shock tube apparatus was utilized to impart controlled shock loading on glass fiber panels having three different thickness: 1.37 mm (panel A), 2.54 mm (panel B), and 4.40 mm (panel C). These panels with an 18.28 mm radius of curvature were held under clamped boundary conditions during the shock loading. A 3D Digital Image Correlation (DIC) technique coupled with high speed photography was used to obtain out-of-plane deflection and velocity, as well as in-plane strain on the back face of the panels. There were two types of failure mechanism observed in all the three panels: fiber breakage and inter-layer delamination. Macroscopic postmortem analysis and DIC results showed that panel C can mitigate higher intensity (pressure) shock waves without initiation of catastrophic damage in the panel. Panel A could sustain the least shock wave intensity and exhibited catastrophic failure.

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