THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING 

GEORGIA INSTITUTE OF TECHNOLOGY   

Under the provisions of the regulations for the degree
 

DOCTOR OF PHILOSOPHY
 

on Tuesday, January 12, 2021

9:00 AM

via 

BlueJeans Video Conferencing 

https://bluejeans.com/502529905

will be held the 

DISSERTATION PROPOSAL 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. Youjiang Wang, MSE

Prof. Antonia Antoniou, ME

Prof. Chaitanya Deo, NRE/ME

Abstract:

Polyethylene (PE) has been extensively used for implants as an acetabular cup in prosthetic hips and as a tibial plateau and patellar surface in prosthetic knees for total joint arthroplasty (TJA) since the mid-twentieth century. Ultra-high molecular weight polyethylene (UHMWPE) and high-density polyethylene (HDPE) have been first adopted by Sir Charnley in the early 1960’s as bearing surfaces against a metallic or ceramic part in the total joint replacement and have been used in clinical practice since then. However, long term clinical use suggests that the friction between these parts leads to the failure of the PE component predominantly through surface wear resulting in release of polymer debris that stimulates osteolysis causing loosening of the implant and eventually leading to its failure. These prosthetics require the PE component to have minimum wear in the directions of joint movement. Hence, tailoring the material response by altering the microstructure via texturing PE during processing to have minimal wear in the essential directions will prove beneficial for improving the durability of PE component and hence the longevity of the implant. 

The objective of this research is to study the effect of texture and microstructure on wear behavior of two types of 3D printed HDPE/UHMWPE/HDPE_wax trimodal reactor blends (containing 10 wt.% of UHMWPE) with varying overall molecular weight along with 3D printed HDPE and compare it to those of injection molded samples. Texture, the preferred alignment of crystallographic orientation in a polycrystalline material, is induced in the polymer samples using additive manufacturing by means of fused filament fabrication (FFF), also known as fused deposition modeling (FDM) and varying 3D printing parameters like printing orientation and printing speed. The texture components are characterized through pole figures and orientation distribution functions (ODFs) using Wide Angle X-ray Diffraction (WAXD). To correlate the texture components with the microstructure of the samples, the morphology of the polymer samples will be studied using an appropriate characterization technique such as TEM/SEM/AFM. To determine the effect of texture on the wear behavior of the polymer samples, the wear properties will be characterized using a NanoTest machine with fretting module. The wear behavior along with friction measurements by varying applied fretting load, fretting frequency/amplitude, wear orientation and number of wear cycles will be studied for the 3D printed and injection molded samples using the nano-fretting module. To calculate the wear volume, the resultant residual depth and width caused by fretting will be determined using confocal microscopy or AFM depending on the residual depth/width range. These results provide the variation of elastic recovery response and friction coefficient with different wear cycle parameters. Additionally, nanoindentation tests will be performed on the 3D printed and injection molded samples using the NanoTest machine’s nanoindentation module to determine the material hardness and elastic modulus variation with residual depth and load. All these results help determine the global effect of texture on wear behavior and other mechanical properties of the 3D printed HDPE/UHMWPE/HDPE_wax trimodal reactor blends.