Doctoral Defense in Mechanical Engineering - Ziwei Lu

Zoom link:
https://eu01web.zoom.us/j/65458318860

Doctoral candidate:
Ziwei Lu

Title of thesis:
Redesign of Plastic Packaging for Fresh Fish Transport Lightweight design of 3-kg EPS boxes and 460-L sandwich-structure PE tubs based on numerical and experimental investigations of thermal and structural behavior

Opponents:
Dr. Maria Charalambides, Professor at the Faculty of Engineering, Imperial College London, United Kingdom
Dr. Ignat Tolstorebrov, Associate Professor at the Faculty of Engineering, Norwegian University of Science and Technology, Norway

Advisor:
Dr. Björn Margeirsson, Guest Associate Professor at the Faculty of Industrial Engineering, Mechanical Engineering, and Computer Science, University of Iceland

Other members of the doctoral committee:
Dr. Fjóla Jónsdóttir, Professor at the Faculty of Industrial Engineering, Mechanical Engineering, and Computer Science, University of Iceland
Dr. Sigurjón Arason, Professor Emeritus at the Faculty of Food Science and Nutrition, University of Iceland
Dr. Ólafur Ögmundarson, Professor at the Faculty of Food Science and Nutrition, University of Iceland

Chair of Ceremony:
Hafsteinn Einarsson

Abstract:
The increasing demand for sustainable cold-chain logistics has created a need for lighter and more environmentally efficient packaging for fresh food transport. This thesis investigates the structural, thermal, and environmental performance of expanded polystyrene (EPS) boxes and rotomolded polyethylene (PE) food tubs used in the transport of fresh fish products. The objective is to develop lighter packaging solutions while maintaining the mechanical strength and thermal insulation required for chilled food distribution. The study combines experimental testing, microstructural analysis, finite element analysis (FEA), and life cycle assessment (LCA) to relate material properties to the overall performance of EPS boxes. Experimental results for EPS boxes show that small density variations significantly increase material modulus, and influence the stiffness and stacking strength of the EPS box. Using a calibrated FEA framework, an improved EPS design achieved an 11% reduction in box weight. This reduced the environmental impact across all major LCA categories while causing a 9% reduction in thermal insulation and negligible decrease in stacking strength. For PE food tubs, microstructural defects in the high-density polyethylene (HDPE) skin layer were found to substantially reduce material ductility. Simulations of industrial hoisting conditions further identified buckling of the handle as the dominant failure mode, providing a clear pathway for geometric optimization of load-bearing capacity in the elastic region. Overall, this work provides scientifically validated design guidelines for more sustainable cold-chain packaging and highlights the importance of advanced material models and stochastic numerical methods capable of accounting for the inherent microstructural variability in PE foams.

About the doctoral candidate:
Ziwei Lu, born in 1993, received her B.Eng. in 2013 from the University of Electronic Science and Technology of China (UESTC) and her M.Eng. in 2017 from Southeast University (SEU), China. Prior to pursuing her doctoral studies, she gained valuable industry experience working as a R&D engineer at AAC Technologies (2017–2019) and as a project manager (PMI certified) at OPPO Communications (2019–2020). Ziwei is married to Hao Geng, who is also a PhD student at the same faculty.