Experiment: Comparing the strength of natural timber and other construction materials

Aim: To compare the strength of some natural timbers and other materials

Materials: Plywood, hard wood cut across the grain, soft wood cut along the grain, soft-wood cut across the grain, softwood cut along the grain, weights, bricks/clamps, plastic, iron/metal with the same dimensions as the wood. You can use other materials with the same dimensions

NB The wood and metal pieces must have the same dimensions for comparisons to make sense

Method

1. Clamp the piece of plywood on a table as shown in the diagram above with about 3/4 of its length overlapping
2. Add weights to the overlapping end about 1 cm from the end until the wood breaks
3. Repeat  using the other pieces of wood of the same size and other materials
4. Turn the plywood and plastic beams on their edges and load them in this position
5. Record the results in a table showing the woods/materials used and the weights necessary to break them

Observations and Results

The greater the depth of a beam the more load it can support

• Hardwood is stronger/stiffer than softwood as the former required a greater load to break
• Timber that is cut along the grain requires less load to break
• All beams required more load to break when turned on a sides that increased their depth (see diagram above)
• The metal beams required the greatest load to break (bend/buckle)

Conclusion

• Hardwood is stronger/stiffer than softwood
• Timber is stronger when it is cut along its grain
• Beams are stronger when they are lying on the side that has the greatest depth

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