04/23/2024
By Danielle Fretwell

The Francis College of Engineering, Department of Mechanical Engineering, invites you to attend a Doctoral Dissertation Proposal defense by Michael Olaya on "Multiscale process modeling of polymer matrix and polymer-derived composites for high-performance applications."

Candidate Name: Michael Olaya
Degree: Doctoral
Defense Date: Friday, May 3, 2024
Time: 10 a.m. to noon
Location: Southwick 240

Committee:

  • Advisor: Christopher J. Hansen, Chair; Professor, Department of Mechanical Engineering, UMass Lowell
  • Scott E. Stapleton, Professor, Department of Mechanical Engineering, UMass Lowell
  • Xinfang Jin, Professor, Department of Mechanical Engineering, UMass Lowell
  • Marianna Maiaru, Professor, Department of Mechanical Engineering, Columbia University
  • Gregory M. Odegard, Chair in Computational Mechanics, Department of Mechanical Engineering-Engineering Mechanics, Michigan Tech
  • David Mollenhauer, Principal Materials Engineer, Air Force Research Lab
  • Trenton M. Ricks, Assistant Project Manager, NASA Glenn Research Center

Brief Abstract:
Polymer matrix and polymer-derived composites serve as fundamental components in the aerospace industry, playing a crucial role in the development of lightweight and high-performance materials for structural components and high temperature applications. The intricacies of the composite manufacturing process significantly influence the final material's structural integrity, thermomechanical properties, and performance. Starting from curing of the polymer matrix, through the fundamental understanding of the mechanisms present throughout each stage of processing, it is possible to tailor the manufacturing in such a way that results in optimal material properties for the specific application while also increasing cost-effectiveness by minimizing processing time and improving the reproducibility of the high-performance composite. Critically, manufacturing is inherently tied across numerous operational length scales within the material (e.g. molecular, fiber, structural); major challenges with the fabrication of optimized, state-of-the-art high-temperature high-strength composites include understanding the polymer constitutive behavior, in situ residual stress generation, failure mechanisms typical of these materials, and developing comprehensive physics-based predictive multiscale modeling frameworks. This thesis focuses on studying the fundamental relationship between materials, microstructure, manufacturing, and performance by integrating physics-based modeling and experimental mechanics with the goal of establishing a coupled thermal-chemical-mechanical computational framework to predict residual stress arising during manufacturing of polymer matrix and polymer-derived composites. First, a novel experimental technique for characterizing polymer material behavior during curing for two-part thermosetting resins is postulated. This method exploits the system chemistry to fabricate time-independent, off-stoichiometry test specimens for intermediate cure state characterization by proxy, circumventing traditional procedures that directly involves the use of the ever-evolving partially cured material. Then, a process modeling approach is proposed to characterize the composite behavior during curing of complex microstructures, including porous matrices and blended tows containing varying fiber materials and geometries, for the purposes of hierarchical multiscale modeling through a high-fidelity finite element (FE) numerical homogenization scheme. This computational scheme leverages computational micromechanics to provide a flexible way to virtually study and characterize the evolution of composite behavior throughout processing, ranging from thermoset curing to pyrolysis of preceramic polymers. Finally, the experimental and computational work is connected, and a hierarchical composite analysis is performed on a novel 3D woven composite designed to act as a thermal protection system (TPS), which features high porosity and a complex blended tow microstructure. State-dependent effective properties are obtained across the porous matrix and blended tow scales using the homogenization strategy set forth by this thesis. In the end, virtual process modeling of the full 3D woven architecture at the mesoscale is achieved through hierarchical multiscaling, where the outputs gathered from analyses at lower length scales serve as inputs to scales above. In future work, the polymer infiltration and pyrolysis (PIP) processing mechanisms shall be studied and implemented into the process modeling framework for the purposes of studying ceramic matrix composites (CMCs). Furthermore, further analysis of the high porous 3D woven composite textile will be investigated to better understand avenues for optimizing thermomechanical performance via tailoring processing parameters.