The Effect of the Stiffness of Unit Load Components on Pallet Deflection andBox Compression StrengthSamantha PhanthanousyThesis submitted to the faculty of the Virginia Polytechnic Institute and State University inpartial fulfillment of the requirements for the degree ofMasters of ScienceInForest and Forest ProductsLaszlo Horvath, ChairMarshall S. WhiteJohn C. BouldinMay 2, 2017Blacksburg, VirginiaKeywords: Packaging, Pallet, Corrugated Box, Load-bridging, Unit load, Compression StrengthCopyright 2017 Samantha Phanthanousyunless otherwise stated
The Effect of the Stiffness of Unit Load Components on Pallet Deflection andBox Compression StrengthSamantha PhanthanousyABSTRACT (Academic)Currently, pallets are designed assuming that the load is distributed evenly on the top ofthe pallet. When pallets are loaded with packages such as corrugated boxes or returnable plasticcontainers, due to their physical shape, packages, are not capable of deforming freely with thepallet and a bridging phenomenon occurs. During this load bridging phenomenon, a portion of thevertical forces are redistributed as horizontal forces which causes the redistribution of the verticalcompression stresses on the pallet towards the support. As a result, the deflection of the pallet candecrease and the load capacity of the pallet can increase significantly. The second chapter of thispaper investigates the effect of package content on pallet deflection. The study concluded thatpackage content did not have a significant effect on pallet deflection within the boundaryconditions of the experiment.The third part of this paper considers how a specific pallet characteristic could affect theway a corrugated box performs. Standard box design procedures include adjustments of estimatedcompression strength for relative humidity, overhang on pallets, vibration, and alignment of boxes.However, there is no adjustment factor for pallet stiffness. The objective of the study described inthis thesis is to find an answer for how the compression strength of a box is affected by palletstiffness and top deckboard twist. The study concluded that the pallet stiffness and top deckboardtwist do not have an effect on the compression strength of the box until less than 12% of the areabox is supported.
ABSTRACT (General Audience)Within the United States alone, there are more than 2 billion pallets in service daily.These pallets transport and store a wide variety of products. There are many factors that couldeffect the performance of a pallet, and it is still unknown which design factors and possiblepackage interactions will or will not effect pallet performance. The first objective of this thesis isto investigate the effect of package content on pallet deflection. The study concludes that thepackage content does not have an effect on pallet deflection.With about 1300 manufacturing plants that produce corrugated in the Unites States andCanada, the industry alone provides 26 billion to economies. Corrugated paperboard boxes areused daily for distribution and packaging, allowing products to easily and safely travel the globe.A majority of the time, these boxes are transported and stored on wooden pallets. Currently,there is no safety factor for box design that takes pallet stiffness into consideration. The secondobjective of this thesis is to investigate the effect of top deckboard twist on box compressionstrength. The results from the study concluded that the pallet stiffness and top deckboard twist donot have an effect on the compression strength of the box until less than 12% of the area box issupported.
Dedicated to my family who taught me the importance of hard work.iv
ACKNOWLEDGEMENTSThis thesis could not have been accomplished without the assistance and guidance fromthose around me. I am tremendously appreciative and grateful for my advisor, Dr. Laszlo Horvath.He has provided me with endless guidance and encouragement. I am not only thankful for theopportunity he provided me in higher education, but for all of his time, effort and wisdom he hasprovided into assisting me during this process. Dr. Marshall S. White provided key suggestionsand insightful comments throughout the research. I am grateful to have had the pleasure and honorof working with such a successful packaging researcher. His knowledge of the packaging worldwas highly respected during this work. I would like to thank Dr. John C. Bouldin for offering anew perspective to the research and providing valuable suggestions to the work. His knowledge ofresearch assisted in furthering this research.I would like to express my gratitude to the faculty, staff, and students of the Department ofSustainable Biomaterials; Rick Caudill, David Jones, and Matt Hixon for helping me prepare anddevelop testing arrangements and Angela Riegel, as well, for her administrative support. I wouldlike to thank Robert Shock for the undergraduate support during the summer. There is muchappreciation for my colleague Eduardo Molina for his friendship and advice through this journey.The advisory members of the Center for Packaging and Unit Load Design at Virginia Techare appreciatively acknowledged for providing financial support for the research performed in thisthesis. Packaging Corporation of America (PCA) was essential in providing research materialsnecessary for the research projects.Dr. Young T. Kim was a key member in directing me into pursuing the packaging degree.I would like to thank him for welcoming me and guiding me at the first steps of my packagingeducation.The most important support was provided by my family and my boyfriend, DustinQuesenberry. Thank you for always believing in me and inspiring me to do my best.v
Table of ContentsChapter 1: Literature Review . 11.1 Corrugated Paperboard Boxes . 11.1.1 Introduction of Corrugated Paperboard Boxes . 11.1.2. Terminology of Corrugated Paperboard Boxes . 21.1.3. Design of Corrugated Paperboard Boxes . 41.1.4. Testing Methods of Corrugated Paperboard Boxes . 41.1.5. Compression Strength of Corrugated Paperboard Boxes . 51.2. Wooden Pallets . 81.2.1. Introduction of Wooden Pallets . 81.2.2. Terminology of Wooden Pallets . 91.2.3. Design of Wooden Pallets . 111.2.4. Testing Methods of Wooden Pallets . 131.3. Unit Loads . 141.3.1. Introduction of Unit Loads. 141.3.2. Design of Unit loads . 141.3.3. Testing Methods of Unit Loads . 151.4. Interaction between Pallets and Packages. 161.5. References . 18Chapter 2: The Influence of Package Content on Pallet Deflection . 232.1. Abstract . 232.2. Introduction . 232.3. Objectives . 252.4. Boundary Conditions . 252.5. Materials and Methods . 252.5.1. Materials . 252.5.1.1. Pallet Segments . 252.5.1.2. Corrugated Boxes. 262.5.2. Methods. 282.6. Experimental Design . 292.7. Statistical Analysis . 302.8. Results and Discussion . 31vi
2.9. Conclusions . 352.10. References . 36Chapter 3: The Influence of Top Deckboard Rotation on Corrugated Box Compression Strength. 383.1. Abstract . 383.2. Introduction . 383.3. Objective . 403.4. Boundary Conditions . 403.5. Materials and Methods . 403.5.1. Materials . 403.5.1.1 Corrugated Paperboard Boxes . 403.5.1.2 Pallet Deckboard Segments . 413.5.2. Methods. 413.6. Experimental Design . 423.7. Statistical Analysis . 443.8. Results and Discussion. 443.9. Conclusions . 483.10. References . 49Chapter 5: Recommendations for Future Studies . 51Appendix A: Results of statistical analysis for analyzing the influence of package content onpallet deflection . 52Appendix B: Results of statistical analysis for analyzing the influence of top deckboard rotationon corrugated box compression strength . 56vii
List of FiguresFigure 1. US Patent 122,023 of corrugated material granted to Albert L. Jones in 1881 . . 2Figure 2. Graphic representation of liner and corrugated medium. . 3Figure 3. Various board styles and flute types of corrugated paperboard . 3Figure 4. Design styles of corrugated boxes . . 4Figure 5. Load-deflection curve of corrugated paperboard box . 7Figure 6. Patent of pallet design created by George Raymond and William House in 1937 . 8Figure 7. Stringer class pallet with labeled components . . 10Figure 8. Block class pallet with labeled components . . 10Figure 9. Representation of four way, partial four way, and two way pallets . . 11Figure 10. Example of heat treatment stamp on a pallet.  . 12Figure 11. Unit load example with labeled stabilizers. . 15Figure 12. Different inside fillers of corrugated paperboard boxes used to simulate the threerigidity levels: A) Rigid, B) Flexible, C) Semi-Rigid. . 28Figure 13. Testing set-up of the effect of packaging stiffness on load bridging. . 29Figure 14. Average deflection plot for box size and pallet stiffness. . 32Figure 15. Image of large corrugated boxes with rigid fill during deflection. 33Figure 16. Image of medium and small corrugated boxes with rigid fill during deflection . 33Figure 17. Testing set-up to record pressure between boxes with 80lb of fill. . 34Figure 18. Experimental setup for the compression strength evaluation using two palletsegments. . 42Figure 19. Percentage of length of sidewall supported investigated. . 43Figure 20. Offset investigated when 47% of length of sidewall is supported. . 43Figure 21. Corrugated box compression strength as a function of percent of sidewall lengthsupported and pallet stiffness. . 46Figure 22. Angle twist of top deckboard based on percentage of length of sidewall supported andpallet stiffness. . 47Figure 23. Graphic representation of method of pallet top deckboard tilt on corrugated box. . 47viii
List of TablesTable 1. Summary table of the adjusted average stiffness values of commonly used pallets. . 26Table 2. Summary table of the stiffness values of 40 in. x 10 in. pallet segment by material. . 26Table 3. Total number of corrugated paperboard boxes and sample weights utilized. . 27Table 4. Experimental design to investigate the effect of packaging stiffness on load bridging. 30Table 5. Average simulated pallet deflections based on box size and package content. . 31Table 6. Pressure Comparison between Experiment Results and Flat crush test results. . 35Table 7. Experimental design to investigate the effect of top deckboard twist on box compressionstrength . 42Table 8. Experimental design of box location offsets used to investigate the effect of palletstiffness on box compression strength when 47% of the length of sidewall is supported. . 43Table 9. Average failure load of the corrugated box based on percent of supported sidewalllength and pallet stiffness. 45Table 10. ANOVA results for the effects of package size, package content, and pallet stiffness onpallet deflection. . 52Table 11. Raw deflection data for all trials of rigid package content. . 53Table 12. Raw deflection data for all trials of flexible package content. . 54Table 13. Raw deflection data for all trials of semi-rigid content. . 55Table 14. ANOVA results for the effect of pallet stiffness and percent of length of sidewallsupported on box compression strength. . 56Table 15. Raw Data for failure load, deflection, and twist angle. for 0.75 in. TDB thickness. . 56Table 16. Raw data for failure load, deflection, and twist angle for 0.5 in. TDB thickness. 58Table 17. Raw data for failure load, deflection, and twist angle for 0.375 in. TDB Thickness. . 60ix
Chapter 1: Literature Review1.1 Corrugated Paperboard Boxes1.1.1 Introduction of Corrugated Paperboard BoxesThe purpose of a corrugated paperboard box is to facilitate product storage and distributionand to protect the product as it moves between supplier and customer. In 1871, Albert L. Joneswas granted the first patent for a corrugated material that is directly connected to what is knowntoday as corrugated boxes. The patent reads as follows, “The subject of this invention is to providemeans for securely package vials and bottles with a single thickness of the packing materialbetween the surface of the article packed it consists of paper, cardboard which is corrugated,crimped or bossed the latter may be made into packing boxes ” . The image of the patentcan be seen in Figure 1. Through multiple patents, researchers were improving corrugated materialover the years, it was in 1914 when the Pridham Decision allowed a breakthrough for the marketof corrugated paperboard boxes. The Interstate Commerce Commission broadened the motorfreight and rail carrier specifications to include corrugated paperboard boxes as shippingcontainers. They also lessened doubts about corrugated paperboard by stating products behavedthe same during shipment regardless of being transported in a wooden or corrugated container .However, it was not until 1970 that corrugated containers began to make a significant presence inthe shipping industry. A third of corrugated containers were used fo