Research Update: New grant from The Pallet Foundation to study alternative fasteners

Our director, Dr. Laszlo Horvath, has received a new research grant from The Pallet Foundation to investigate to predict the rotational stiffness of pallet joints made using alternative fasteners (Image 1) including lag screws and carriage bolts. This project will investigate and validate the applicability of the findings of previous researchers, Loferski and Gamalath, who designed a model to predict the rotational stiffness of pallet joints based on the traditionally used fasteners such as pallet nails.

Although wood pallets are most-commonly assembled with nails, heavy-duty pallets and special-purpose pallets are often assembled with other fasteners such as lag screws and carriage bolts. The strength of these types of alternative fasteners has been well documented in the literature and design codes, but the stiffness of the resulting pallet joints has never been evaluated. The model developed by Loferski and Gamalath to predict joint stiffness was never validated for pallet joints made with alternative fasteners. Therefore, the goal of this project will be to investigate the rotational stiffness of pallet joints made with lag screws and carriage bolts and to evaluate the applicability of the model developed by Loferski and Gamalath to predict the rotational stiffness of these pallet joints.

A total of six, alternative fastener designs will be investigated including lag screws (sizes 0.25”, 0.375”, and 0.5”) and carriage bolts (sizes 0.25”, 0.375”, 0.5”). In order to simulate a range of wood density values, wood species with various specific gravity values will be investigated including: kiln-dried softwood, green softwood, and green hardwood. All wood samples will be measured and conditioned to make sure that the dimensions and the moisture content of the wood is known and consistent. Head embedment stiffness tests, shank withdrawal stiffness tests, as well as moment-rotation tests will be conducted on multiple samples of the alternative fasteners.

Joe Keller (Charlottesville, Virginia) (Image 2), a recent graduate of the Packaging Systems and Design program at Virginia Tech, has been selected to work on the research project. Joe started his Master’s research project during the Fall of 2021 and expected to graduate by May 2023. The information obtained from Keller’s research project will be built into The Pallet Design System, so it will allow future pallet designers to better design wood pallets using lag screws and carriage bolts.