ASTM D3332 outlines three test methods (A-C) for determining the fragility of products to be packaged for shipment in the distribution environment. Method A is used when information on drop heights is limited. Method B is used when drop heights are known with great certainty. Method C is used for relatively rugged (low fragility) products that may not need cushioning.
Under all three methods, the test product is fastened to the carriage of a shock test machine. The machine is set to attain a velocity change which exceeds the minimum required to damage the product, but at a very low acceleration level. Then, when the carriage is dropped, the product is examined for product damage. If none occurs, the machine is reset for a higher maximum acceleration and the test is repeated (at the same drop height). The maximum acceleration at which product damage first occurs is the fragility of the product in the direction tested.
As you learned earlier, the determination of fragility is the first step in cushion design; without this information, you can't determine the cushion thickness that will adequately protect your product.