03/19/2026
By Danielle Fretwell

The Francis College of Engineering, Department of Plastics Engineering, invites you to attend a Doctoral Dissertation defense by Matthew Drew on: "Optical and Adhesion Properties of Laminated Polymer/Sapphire Composites."

Candidate Name: Matthew Drew
Degree: Doctoral
Defense Date: Tuesday, March 31, 2026
Time: 1 - 3 p.m.
Location: ETIC 445

Committee:

  • Advisor: Davide Masato, Ph.D., Associate Professor, Plastics Engineering, University of Massachusetts Lowell
  • Alireza Amirkhizi, Ph.D., Professor, Mechanical Engineering, University of Massachusetts Lowell
  • Stephen Johnston, Ph.D., Professor, Plastics Engineering, University of Massachusetts Lowell

Abstract:
The demand for lightweight, impact-resistant, and optically clear protective eyewear has led to the development of transparent composites that combine the complementary properties of polymer and ceramic glasses. This dissertation investigates the optical, adhesion, and ballistic properties of laminated sapphire/polycarbonate composites designed for protective eyewear applications. The work integrates experimental characterization and numerical modeling to establish relationships between processing, structure, and properties affecting optical quality, interfacial adhesion, and mechanical reliability.

The first section focuses on the influence of mold surface plating on residual stress and birefringence in injection molded optical grade polycarbonate lenses. Nickel-plated mold inserts were shown to influence the thermal contact resistance at the polymer/mold interface, reducing heat transfer during filling and delaying skin layer formation. This allowed greater polymer chain relaxation during the cooling process. Photoelastic stress analysis and calibrated Moldex3D simulations confirmed that changes in interfacial heat transfer significantly influences residual stress and birefringence, demonstrating that mold surface engineering is an effective strategy for improving optical performance in injection molded lenses.

In the second section, the other layers of the composite are also tested. The adhesion strength of laminated sapphire (SA)/thermoplastic polyurethane (TPU)/polycarbonate (PC) composites were characterized using a double-lap shear joint (DLSJ) methodology. Lamination pressure and temperature significantly influenced the adhesive flow, bond-line thickness, and shear strength of the composites. Increased pressure and temperature reduced bone-line thickness and improved load transfer by enhancing consolidation and surface contact between the adhesive and adherend. Statistical analysis identified pressure as the dominant factor that affects adhesion shear strength. Failure consistently occurred at the SA/TPU interface, highlighting the adhesion asymmetry in the SA/PC composite and the importance of mitigating that asymmetry through processing.

The third section focused on the adhesive interlayer thickness in the composite lens by characterizing the optical transmission, distortion, and high-velocity impact response. Optical characterization included measurements of light transmission and distortion to determine how adhesive thickness influenced the refractive index matching, haze, and image clarity. Variations in bond-line thickness were shown to alter the optical path length and contribute to localized distortions. High-velocity impact testing was conducted using Photonic Doppler Velocimtry (PDV) to measure the effect of adhesive thickness on the back-face velocity and displacement. The laminated system demonstrated synergistic mechanical behavior, in which SAe provided hardness and initial impact resistance, while TPU and PC accommodated deformation and mitigated catastrophic fragmentation. The results highlight the importance of controlling the adhesive thickness during lamination to simultaneously optimize transparency and impact performance in SA/PC composites.

Overall, this dissertation demonstrates that the performance of transparent SA/PC composite lenses is governed by thermos-mechanical and interfacial phenomena injection molding, lamination, and overall design. The results provide design and processing guidelines for the development of lightweight, transparent, impact-resistant laminated SA/polymer composites.