Upcoming Event: PhD Dissertation Defense

Controlling and Exploiting Heterogeneity in Thermoplastic Composites

Joseph Kirchhoff, CSEM Graduate Student

Abstract

High-rate processing of thermoplastic composites promises dramatic gains in manufacturing speed and energy efficiency, yet sub-second processing windows often limit reliable interlayer bonding. In semicrystalline polymers, crystallinity is essential for long-term performance but restricts chain mobility, creating a fundamental tension between manufacturability and structural integrity. In this talk, I address this challenge with OATMEAL, a thermoplastic prepreg engineered to consolidate in a sub-melt Goldilocks zone that preserves beneficial crystallinity while enabling robust interlayer fusion. Through high-rate vacuum-bag processing and in-space welding demonstrations, I show that this approach achieves faster, more energy-efficient consolidation without compromising mechanical performance. Complementing these experiments, I use computational inverse methods to uncover physics, such as polymer diffusion during OATMEAL manufacturing. Inverse methods extract meaningful insights from noisy, typically sparse data, and when formulated carefully, they can infer high-dimensional spatial fields. For example, image-based inversion allows us to infer extremely high-dimensional elastic and Poisson fields, discretized into over 300,000 degrees of freedom, providing context and a foundation for predictive, high-throughput manufacturing with in-process monitoring. These methods are applied to 3D printed heterogeneous samples in addition to scanning electron microscopy testing. I aim to not only reimagine thermoplastic composite fabrication but to one day modernize manufacturing across fields.

 

Contact: kirchhoff@my.utexas.edu

Biography

Joseph Kirchhoff is a NASA Space Technology Graduate Research Opportunities (NSTGRO) fellow and PhD candidate in Mechanical Engineering at the University of Texas at Austin, co-advised by Dr. Omar Ghattas and Dr. Mehran Tehrani. His research while focusing on thermoplastic composites spans inverse problems and PDE-constrained optimization for physics-based digital twins. He is the co-inventor of OATMEAL, a thermoplastic prepreg technology aimed at enabling significantly faster, lower-energy composite manufacturing. He is a recipient of the American Society for Composites PhD research scholarship, NSF GRFP, and multiple SAMPE paper awards. 

In his free time, he guides mountain biking, canoeing trips and enjoys connecting with people through the outdoors in addition to research.