The effect of water content on compressive strength and impact properties of new softwood pallets was determined through four experiments. A static compression test was performed on pallet specimens with various water contents. The compressive strength drop rate was 3.4 pounds per square inch (23442 Pascal) per 1% increase of water content. A drop test was performed on pallet specimens with various water contents and cushioning materials at 12-inch (0.3048-meter) drop height. Impact acceleration increased at the rate of 0.14g per 1% increase in water content. A drop test was also performed on pallet specimens with various water contents at 18-inch (0.4572-meter) drop height. Energy absorption reduced at the rate of 0.16% per 1% increase of water content. Thus, softwood pallets, which are often left outdoors and subjected to rain water, have two potential problems with the increase in water content, i.e., reduction in compressive strength under static loading and increase in impact acceleration felt by boxes on these pallets.

Wood pallets are often put in circulation for several years. In a pallet's lifetime it goes through several wet-dry cycles. In this study, softwood pallet specimens were compressed statically and impacted at different water contents through an accelerated drying process for three repeated wet-dry cycles. A static compressive strength test was performed along the grain of pallet stringers to avoid the effect of loadings in different grain directions. Instead of using the standard drop test from a drop tester, an incline impact test was performed to obtain more consistent impact accelerations. Impact data was recorded by a shock recorder to simplify the set up for the experiment. This study has found that there is no significant effect of the wet-dry cycles on static compressive strength and impact acceleration.

The first part of this study verifies that static compressive strength of new wooden pallets decreases as temperature increases. The drop of compressive strength is at a small rate of 0.61 psi per 1°F of temperature increase within the temperature range of 80°F to 160°F. This is consistent with the current timber structural design practice. The strength reduction is small and has little effect on pallet static compression performance. The second part of this study investigates impact acceleration from free-fall drop tests performed at temperatures ranging from 80°F to 160°F. As temperature rises, specimens become weaker thus they absorb more impact energy, which results in lower impact acceleration. The drop of impact acceleration is also at a small rate of 0.034g per 1°F of temperature increase. When temperature rises from normal temperature of around 80°F to a high temperature of 160°F, the impact acceleration reduces about 2.72g. This rise results in less potential damages on products on the pallet. The third part of this study looks at the impact acceleration due to horizontal impact due to a forklift at a lower range of temperature of 33°F to 72°F. The drop of impact acceleration is at a faster rate of 0.674g per 1°F of temperature increase. When temperature drops from 59°F to 48°F, the impact acceleration increases about 7.41g. This increases the damage potential of products on pallets.

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