Damage and failure modelling of composites
Despite the high penetration of composite materials in new aircraft, manufacturers still rely heavily on empirical methods that cannot accurately predict the response of composite materials to external loads. The ability to accurately model composite fracture would allow significant airframe weight savings and improvements in the design of the material itself. Within the project MULTIFRAC (Multiscale methods for fracture), scientists produced advanced models describing material failure integrated into a design framework that enables the computational design of new materials. Project members developed computational methods for fracture analysis of carbon nanotubes for polymer reinforcement on several length scales. Simulations conducted on the nanoscale helped predict for instance the behaviour of the interface between the polymer and the carbon nanotube. The team then used a concurrent coupling technique to embed fine-scale domains around the macroscopic fracture, considering the rest of the domain as a homogenised material. This approach was subsequently refined to describe more complex fracture patterns on the fine scale and then scale them up into simple patterns on the macro level. Material properties in domains far away from the macroscopic fracture were scaled by either a hierarchical or a semi-concurrent approach. Experiments conducted kept pace with simulation results. Composite materials in aircraft construction have demonstrated their potential for making lighter aircraft that burn less fuel. Sufficiently understanding their tolerance to damage, manufacturers will be able to improve composite design, making aircraft safer.
Keywords
Damage, failure modelling, composite materials, aircraft, fracture, MULTIFRAC
