Crush Stress & SEA Testing
Measuring Dynamic Properties of Composites for Crash Modelling
Composites offer huge advantages in crash safety applications through their high specific energy absorption (SEA). A composite crash structure can be a fraction of the weight of a metal one for equal performance and take up less internal space. However, their crash performance is dependent on many factors including impact velocity, fibre orientation and geometry.
Engenuity is one of the world’s leading organisations in the characterisation and prediction of crash performance of composites. We can help you in choosing, testing and characterising the best materials for efficient safety systems for passengers, batteries, hydrogen storage and critical systems.
Material Cards for Crash Modelling
Even very similar composite materials can perform very differently in crush, this is unrelated to their static mechanical properties. Engenuity uses crush screening to select those that are ideal crushing materials, grading materials into 3 different types. Type 1 materials provide a consistently high crush stress, these are recommended for all crash applications including demanding locations under axial load. Type 2 gives an initial high crush stress, but this then reduces as the crushing continues, these materials can be used in crush applications but there are better alternatives. Type 3 materials do not absorb much energy as they fail and therefore do not contribute to the safety of the vehicle during a crash event.
Geometry Effects of Energy Absorption in Crash
It has long been claimed that SEA (and therefore crush stress) is not a material property as it can vary with component geometry. Engenuity has overcome this using two different values in simulation, a delamination free crush typical of flat samples and delamination suppressed crush typical of curved profiles. This approach has been validated through both component and vehicle level physical testing.
Engenuity has also developed a methodology to generate both values directly from flat plaques as shown in the video below.