How is the behaviour of wood parallel to the grain different

How is the behaviour of wood parallel to the grain different from that perpendicular to the grain? Answer this question briefly based on their ultimate strength and Young\'s modulus.

Solution

Think of wood as a bunch of drinking straws glued together parallel to each other.

Along the length of the straws, the tensile strength of the straws makes it hard to break the construct.

Perpendicular to the straws, the glue doesn\'t have much tensile strength. It\'s very easy to break one straw from another by flexing and pulling perpendicular to the grain.

In wood, the straws are lignin and the glue is cellulose. In an intact branch, the lignin fibres are arranged radially around the centre so the branch can bend in any direction.

Once you cut a flat slab, the lining is no longer supported in the axis perpendicular to it\'s run, so that axis becomes vulnerable to being pulled apart when flexed.