Skip to Main Content
 

Global Search Box

 
 
 
 

ETD Abstract Container

Abstract Header

A High Strain-Rate Investigation of a Zr-based Bulk Metallic Glass and an HTPB Polymer Composite

Sunny, George Padayatil

Abstract Details

2011, Doctor of Philosophy, Case Western Reserve University, EMC - Mechanical Engineering.

High strain-rate tests are performed on LM-1 using a Split-Hopkinson Pressure Bar (SHPB) to investigate effects of L/D ratio and annealing. An ultra high-speed camera was also employed to record the deformation and failure processes of LM-1. The amorphous specimens exhibit a reduction in peak stress with reduced L/D ratio and failure at the specimen-insert interface, indicative of stress concentrations due to the difference in the specimen and insert diameters, while the annealed specimens exhibited extensive fragmentation. The stress concentrations in the specimen motivated simulations using LS-DYNA to design new inserts. A tapered insert design was chosen to reduce stress concentrations on amorphous and annealed specimens. Strain gages were also attached to as-cast specimens to determine the elastic stress-strain response. As-cast and annealed specimens with tapered inserts exhibit failure in the gage section, and a comparison of the peak stresses from quasi-static and pressure-shear plate-impact experiments to those in the current study indicate a negligible strain-rate sensitivity of LM-1.

Additional experiments are carried out using a modified SHPB to investigate the loading-rate sensitivity of notched LM-1 specimens. An ultra high-speed camera is employed to provide images synchronized with load-displacement traces from a high-bandwidth oscilloscope. No loading-rate sensitivity on the fracture toughness was observed. Experiments are also conducted to induce damage into notched LM-1 specimens without causing catastrophic failure; a damage zone is present in the specimens and slip-line fields are created which are consistent with those expected in an elastic-perfectly plastic material. Finally, experiments conducted to load previously damaged LM-1 samples indicate an increase in the fracture toughness and energy required to induce catastrophic failure.

Finally, high strain-rate compression experiments are conducted on a hydroxy-terminated polybutadiene (HTPB) polymer and its composite using another modified SHPB for testing of soft materials. Results from the experiments on HTPB polymer indicate a transition in the polymer between low and high strain-rate sensitivity at 2100/s, along with axial splitting at strain-rates above 3000/s. On the other hand, reduced rate-sensitivity is observed in the HTPB composite, most likely due to the presence of numerous interfaces between the glass beads and the polymer binder.

Vikas Prakash, PhD (Committee Chair)
John Lewandowski, PhD (Advisor)
Jennifer Jordan, PhD (Advisor)
Joseph Mansour, PhD (Committee Member)
Xiong Yu, PhD (Committee Member)
301 p.

Recommended Citations

Citations

  • Sunny, G. P. (2011). A High Strain-Rate Investigation of a Zr-based Bulk Metallic Glass and an HTPB Polymer Composite [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1295634962

    APA Style (7th edition)

  • Sunny, George. A High Strain-Rate Investigation of a Zr-based Bulk Metallic Glass and an HTPB Polymer Composite. 2011. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1295634962.

    MLA Style (8th edition)

  • Sunny, George. "A High Strain-Rate Investigation of a Zr-based Bulk Metallic Glass and an HTPB Polymer Composite." Doctoral dissertation, Case Western Reserve University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1295634962

    Chicago Manual of Style (17th edition)