03/20/2026
By Danielle Fretwell

The Francis College of Engineering, Department of Plastics Engineering, invites you to attend a Doctoral Dissertation defense by Rebecca Olanrewaju on: "The Design and Processing of High Performance Architected Composites via Shape Forming Elements."

Candidate Name: Rebecca Olanrewaju
Degree: Doctoral
Defense Date: Friday, April 3, 2026
Time: 11 a.m. - 1 p.m.
Location: ETIC 245

Committee:

  • Advisor: David Kazmer, Professor, Plastics Engineering, University of Massachusetts Lowell
  • Thao (Vicky Nguyen), Professor, Mechanical Engineering, Johns Hopkins University
  • Margaret Sobkowicz Kline, Professor, Plastics Engineering, University of Massachusetts Lowell
  • Jay Park, Associate Professor, Plastics Engineering, University of Massachusetts Lowell

Abstract:
Immiscible polymer blends offer a versatile platform for combining complementary polymer properties, but their performance is often limited by weak interfacial adhesion and uncontrolled phase morphology. Traditional strategies to improve mechanical performance typically rely on chemical compatibilizers or fillers, which add complexity and constrain design flexibility. An alternative approach is to use processing to impose deliberate internal architectures that enhance mechanical performance by controlling phase morphology and interaction.

This dissertation investigates architected immiscible polymer blends in which internal phase geometry is controlled through extrusion based processing techniques. The work explores three interconnected phases of research. The first phase demonstrates that layer multiplying elements (LMEs) can amplify interfacial area and refine phase morphology in polycarbonate (PC) and liquid crystalline polymer (LCP) blends. Mechanical testing shows that LMEs influence modulus, strength, and strain at break by modifying morphology, establishing interfacial architecture as a key design variable.

The second phase introduces shape forming elements (SFEs) to impose deterministic, complex cross-sectional geometries. Coextrusion flow is manipulated to redistribute phases within the die, producing structured architectures that go beyond simple layering. Experimental validation using a piston driven polymer clay extruder and ANSYS Polyflow confirms that SFEs enable reproducible control of phase placement, representing a shift from randomized morphology to a more deliberately engineered architecture. Mechanical testing reveals that the properties of SFE generated blends generally fall between those of the neat polymers, with failure largely governed by delamination at interfaces.

Motivated by these observations, the third phase develops a design methodology for interlocking architectures that aim to mitigate interfacial failure without chemical compatibilizers. By maximizing the perimeter to area ratio of coextruded phases, internal geometries are created that promote mechanical interlocking and structural integrity. This approach demonstrates how geometric design can be used to enhance load transfer and adhesion in immiscible polymer systems, providing a pathway for achieving predictable mechanical performance through architecture rather than chemistry.

Overall, this dissertation establishes a process-structure-property framework for architected polymer composites, illustrating that the internal geometry of immiscible blends can be intentionally engineered to control mechanical response. The findings highlight the potential of extrusion based processing as a tool for materials design and provide a foundation for future work in architected multiphase polymer systems where adhesion is achieved through geometry and processing rather than chemical modification.