GEORGIA INSTITUTE OF TECHNOLOGY    

Under the provisions of the regulations for the degree
  

DOCTOR OF PHILOSOPHY
  

on Thursday, November 18, 2021 

9:30 AM 

via  

BlueJeans Video Conferencing  

https://bluejeans.com/510590927/7173 

will be held the  

DISSERTATION DEFENSE

for  

Sahitya Movva  

  “Influence of Texture on Wear Behavior of 3D Printed HDPE/UHMWPE Bioimplant Material”    

Committee Members:

Prof. Karl Jacob, Advisor, MSE 

Prof. Hamid Garmestani, Co-advisor, MSE 

Prof. Chaitanya Deo, NRE/ME/MSE 

Prof. Antonia Antoniou, ME 

Oomman Thomas, Ph.D., MSE/Coim USA 

Abstract:

Polyethylene is extensively used for implants in total joint arthroplasty. However, long-term clinical use suggests that surface wear of PE causes eventual implant failure. Hence tailoring the material response by altering microstructure via texturing to have minimal wear is beneficial to improve PE component’s durability and hence the implant’s longevity. In this study, the effect of texture and microstructure on wear behavior of two types of 3D printed HDPE/UHMWPE/HDPE_wax trimodal reactor blends with varying overall molecular weight M_w along with 3D printed HDPE has been investigated and compared to that of injection molded samples. Texture has been induced in the polymer samples using injection molding or fused deposition modeling where 3D printing speed and orientation have been varied. The texture components have been characterized through pole figures and orientation distribution functions using Wide Angle X-ray Diffraction. To determine the effect of texture on the wear behavior of the polymer samples, the wear properties at different loads, frequencies, fret orientations and number of fret cycles have been characterized using NanoTest’s fretting module. The morphological features have been investigated using SEM and TEM. The thermal and mechanical properties have been characterized using DSC, DMA and  microindentation. The trimodal blends showed presence of extended-chain UHMWPE and the wear resistance of the blends has been found to be greater than that of HDPE in almost all cases. Presence of UHMWPE increased the hardness and elastic modulus measured from indentation compared to HDPE and increase in M_w of trimodal blend further increased these properties. The bulk density, a physical property, has been measured using a density meter to look at its correlation with mechanical properties but not much correlation was found. Overall, this work helps determine the global effect of texture on wear behavior and other physical, thermal, mechanical properties of the 3D printed HDPE/UHMWPE/HDPE_wax trimodal reactor blends useful to improve the longevity of implants.