Abstract: A method of calculating an impact resistance of a structure undergoing an impact with an impact surface is disclosed. The structure includes a first part bonded or secured to a second part, at least the first part comprising a material having a crush failure mode. The method comprises: a) determining that a finite element representing a portion of the first part is experiencing conditions which dictate that it will undergo the crush failure mode; b) determining a behaviour of the structure assuming it is subject to: i) an ongoing resistance force representing the crush failure mode of the element; and ii) a further force F acting on the first and second parts in a direction tending to separate them.

Abstract: A method of determining the impact resistance of a structure including a crushable material comprises the steps of determining for one or more layers of a finite element of said material during an impact whether said element or layer thereof is to be treated as failing by crushing. If the element or layer is determined to fail by crushing, a load-bearing portion of the structure is defined and the load-bearing portion is treated for the purpose of subsequent calculations as exhibiting an ongoing resistance.