Numerical and experimental performance evaluation of ventilated packages by Tobi Samuel Fadiji Dissertation presented for the degree of Doctor of Philosophy in the Faculty of Engineering at Stellenbosch University Supervisors: Prof. Corné Coetzee Prof. Umezuruike Linus Opara April 2019 Stellenbosch University https://scholar.sun.ac.za DECLARATION By submitting this dissertation electronically, I declare that the entirety of the work contained therein is my own, original work, that I am the sole author thereof (save to the extent explicitly otherwise stated), that reproduction and publication thereof by Stellenbosch University will not infringe any third party rights and that I have not previously in its entirety or in part submitted it for obtaining any qualification. This dissertation includes three original papers published in peer-reviewed journals or books and three unpublished publications. The development and writing of the papers (published and unpublished) were the principal responsibility of myself and, for each of the cases where this is not the case, a declaration is included in the dissertation indicating the nature and extent of the contributions of co-authors. Date: April 2019 Copyright © 2019 Stellenbosch University All rights reserved i Stellenbosch University https://scholar.sun.ac.za Plagiaatverklaring / Plagiarism Declaration 1 Plagiaat is die oorneem en gebruik van die idees, materiaal en ander intellektuele eiendom van ander persone asof dit jou eie werk is. Plagiarism is the use of ideas, material and other intellectual property of another’s work and to present is as my own. 2 Ek erken dat die pleeg van plagiaat 'n strafbare oortreding is aangesien dit ‘n vorm van diefstal is. I agree that plagiarism is a punishable offence because it constitutes theft. 3 Ek verstaan ook dat direkte vertalings plagiaat is. I also understand that direct translations are plagiarism. 4 Dienooreenkomstig is alle aanhalings en bydraes vanuit enige bron (ingesluit die internet) volledig verwys (erken). Ek erken dat die woordelikse aanhaal van teks sonder aanhalingstekens (selfs al word die bron volledig erken) plagiaat is. Accordingly all quotations and contributions from any source whatsoever (including the internet) have been cited fully. I understand that the reproduction of text without quotation marks (even when the source is cited) is plagiarism. 5 Ek verklaar dat die werk in hierdie skryfstuk vervat, behalwe waar anders aangedui, my eie oorspronklike werk is en dat ek dit nie vantevore in die geheel of gedeeltelik ingehandig het vir bepunting in hierdie module/werkstuk of ‘n ander module/werkstuk nie. I declare that the work contained in this assignment, except otherwise stated, is my original work and that I have not previously (in its entirety or in part) submitted it for grading in this module/assignment or another module/assignment. TS Fadiji April 2019 Voorletters en van / Initials and surname Datum / Date Copyright © 2019 Stellenbosch University All rights reserved ii Stellenbosch University https://scholar.sun.ac.za PAPER CONTRIBUTION DECLARATION Declaration by the candidate Declaration with regard to parts of the dissertation in which, in addition to the candidate, other authors were involved. With regard to the following chapters in the dissertation, the nature and scope of my contribution were as follows: Extent Dissertation Chapter Contribution Nature (~%) Chapter 2 Main author and Primary Researcher 75% Chapter 3 Main author and Primary Researcher 70% Chapter 4 Main author and Primary Researcher 70% Chapter 5 Main author and Primary Researcher 75% Chapter 6 Main author and Primary Researcher 80% Chapter 7 Main author and Primary Researcher 80% The following co-authors have contributed to the following chapters in the dissertation: Name e-mail Chapters Contribution Extent (~ %) 10 %, 10 %, 10 %, 10 %, C. Coetzee [email protected] 2,3,4,5,6,7 Advice/Mentoring 10 %, 10 % respectively 10 %, 10 %, 10 %, 10 %, 10 %, U. L. Opara [email protected] 2,3,4,5,6,7 Advice/Mentoring 10 % respectively 5 %, 5 %, 5 %, 10 % T. M. Berry [email protected] 2,3,4,5 Advice/Mentoring respectively A. Ambaw [email protected] 3,4 Advice/Mentoring 5 %, 5 % respectively Signature of candidate: Date: 25-02-2019 Declaration by the candidate The undersigned hereby confirm that: 1. The declaration above accurately reflects the nature and extent of the contributions of the candidate and co-authors to the Chapters as indicated in the table above, 2. No other authors contributed to Chapters as indicated, besides those specified above, 3. Potential conflicts of interest have been revealed to all interested parties and that the necessary arrangements have been made to use the material indicated in the table above in the relevant Chapters of this dissertation. Name Signature Institutional Affiliation Date C. Coetzee Signed electronically Stellenbosch University 25-02-2019 U. L. Opara Signed electronically Stellenbosch University 25-02-2019 T. M. Berry Signed electronically Stellenbosch University 25-02-2019 A. Ambaw Signed electronically Stellenbosch University 25-02-2019 iii Stellenbosch University https://scholar.sun.ac.za ABSTRACT Packaging serves a crucial role in reducing postharvest losses, particularly in the handling of fresh horticultural produce, and would be difficult to do without. Packaging protects the produce against mechanical hazards such as compression, impact, drop or vibration during distribution, ensuring its safe delivery to the consumers in a sound condition, at a minimum cost. Ventilated corrugated paperboard (VCP) packaging is being used extensively for handling fresh produce due to its capability to promote uniform and rapid cooling. However, the presence of ventilation openings jeopardises the strength of the package which could result in produce damage. As it is of utmost importance to ensure that the produce reaches its final destination without damage, continuous improvement in the package strength is paramount. Hence, this project aimed to gain a better understanding of the structural performance of VCP packaging to enhance the development of better and improved package designs. Firstly, a validated finite element analysis (FEA) model was developed to study the structural performance of an existing VCP package. This model incorporated some geometrical nonlinearities of the package. Paper and paperboard characterisations were done to determine the tensile properties, edge compression resistance and flat crush resistance. The tensile properties were used as input parameters in the model. The model was able to predict the compression strength of the package, and showed good agreement with experimental results, within 10%. Package liner thickness had a linear relationship with the compression strength. The stress in the package was found to be concentrated and a maximum at the corners. Subsequently, the FEA model was used to assess the strength of different package designs with emphasis on the influence of different geometrical configuration. The model was validated with experimental results. Increasing the vent area of the package reduced its compression strength. Packages manufactured with double- walled corrugated board performed better than single-walled board irrespective of the design, with the difference in strength as high as 72%. This study showed the importance of knowing the paperboard properties in the design of a package to improve its strength. Furthermore, the creep behaviour of different package designs was evaluated, and results showed load and environment conditions as significant factors affecting the creep rate. Increasing the applied load and relative humidity (RH) as well as reducing the temperature, accelerated the creep rate of the package. Also, package configuration also had a significant effect on the creep rate. Finally, to understand the deformation phenomenon of packages subjected to compression load, the displacement field of different designs was studied using digital image correlation (DIC), a full-field non-contact optical measurement technique. Findings showed that the distribution of the package displacement is iv Stellenbosch University https://scholar.sun.ac.za largely heterogeneous. The displacement field in the out-of-plane direction was the largest while that in the horizontal direction was the smallest. Buckling was found to be a predominant phenomenon occurring at the centre of the package panels. Overall, this study provided empirical and numerical evidence for the design of improved packages, balancing the need for adequate structural performance and optimum cooling functionalities of the package. v Stellenbosch University https://scholar.sun.ac.za OPSOMMING Verpakking speel 'n deurslaggewende rol in die vermindering van na-oesverliese, veral in die hantering van vars tuinbouprodukte, en dit sal moeilik wees om daar sonder klaar te kom. Verpakking beskerm die produk teen meganiese skade as gevolg van druk, impak, val of vibrasie tydens verspreiding. Dit verseker die veilige aflewering van die produk, in ‘n veilige toestand en teen minimum koste, aan die verbruiker. Geventileerde gegolfde karton (GGK) verpakking word omvattend gebruik vir die hantering van vars produkte as gevolg van sy vermoë om uniforme en vinnige verkoeling te bevorder. Die teenwoordigheid van ventilasie openinge belemmer egter die sterkte van die verpakking wat tot skade aan die produk kan lei. Aangesien dit van uiterste belang is om te verseker dat die produk sy eindbestemming sonder skade bereik, is voortdurende