Material properties for load spreading
Also called Density, Compressive strength, Tensile strength, Modulus of elasticity, Young’s modulus, Stiffness versus strength
The four properties that decide how a mat or pad behaves under a crane: compressive strength, the stress a material carries before it crushes; tensile strength, the stress it carries in tension before it fails; modulus of elasticity, how much it deflects elastically before either happens; and density, how heavy it is to handle. Strength and stiffness are independent — a material can be strong and flexible, or stiff and brittle — and both matter, because a mat that has not failed can still deflect enough to concentrate its load.
In practice
Compressive and tensile strength are usually quoted in megapascals (MPa), equivalently newtons per square millimetre (N/mm²); modulus of elasticity in the same units but with much larger figures, because it describes stiffness rather than failure; density in kilograms per cubic metre (kg/m³). Materials behave very differently in tension and compression, so which one governs depends on how the component is loaded — a mat spanning a soft spot works in bending, meaning both, at different faces of the same panel.
Where this comes from: Standard materials engineering usage, as covered under material specification in our CPD-accredited seminar on specifying outrigger mats. Values for a specific product come from that product’s specification, not from a class of material.
Where it matters on site
Comparing mats on one property is how the wrong mat gets bought. A material with excellent compressive strength can still be too flexible to spread a foot load as assumed; a stiff material can be too heavy for two people to place, which changes the set-up method and its cost. Density is not a performance figure at all, but it is often the one that decides whether a set can be handled by hand — and handling is the property people live with every day.