COMPOSITES ANALYSIS

Composite Crush Testing

Obtaining the correct material data is essential to composite impact analysis. The mechanism for efficient composite crush is very different to the plastic folding seen in metallic crush members – instead the composite material undergoes a continuous fragmentation at the crush front or crush zone.
A successful composite crush structure can absorb a great deal more energy per kg than the equivalent steel or aluminium structure. With good material choices and geometry development the composite crush member can realize Specific Energy Absorption (SEA) levels in excess of 100 kJ/kg.

At the outset of designing composite crash structures, good material selection is essential, and in choosing the right material the measured crush stress is key, along with the stability of the crush value and its ratio to the compressive stress of the material. Material crush performance, characterised as crush stress, cannot be derived from the other ‘regular’ material properties such as compressive strength, inter-laminar strength and so on, it has to be measured from physical testing.

Engenuity have developed specialist fixturing for measuring the materials crush stress, crush stability and compressive strength from low cost flat panel coupons. We perform composite crush test screening to guide the material selection process and subsequently fully characterise the crush characteristics of the chosen material for input to the crash analysis of the composite structure. The crush stress of a material is affected by the impact velocity and the type of crush, whether it is delamination dominated or delamination suppressed which is the typical mode for corners or tubes, see Flat vs Curved.

Using our specially developed crush test fixtures, Engenuity have performed thousands of crush tests on hundreds of materials for research and on behalf of our clients for component development. All we need to begin testing are suitably sized flat sheets of candidate materials. From receipt of materials we take care of specimen preparation, crush testing and data analysis and deliver results within 3 weeks on a standard service.

For clients who have access to either a drop tower or servo hydraulic dynamic compression testing apparatus the fixturing we have developed is available for purchase.