Damage initiation and failure mechanisms of carbon nanoparticle modified CFRP up to very high cycle fatigue-loading

The influence of different carbon nanoparticles like multi-walled carbon nanotubes and few layered graphene on the damage initiation and failure mechanisms of carbon fibre reinforced plastic (CFRP) under static and fatigue loading up to the very high cycle fatigue regime is investigated. Quasi-static mechanical properties of cross-ply laminates are not affected by the nanoparticle modification but an improvement of fatigue life and change in dominating damage mechanism due to the nanoparticle modification can be achieved. Fracture toughness tests with CFRP in mode I and mode II show an influence of the orientation of the particles with regard to the crack growth direction and on the surface roughness. Hence, the toughness increases. Fractography analysis by scanning electron microscopy (SEM) reveals increased plastic deformation with a rougher fracture surface and thus higher energy absorption due to the nanoparticles. Nanoparticles act as crack initiators and consume fracture energy. Different energy dissipation mechanisms at the nanoparticles, depending on their structure, are discussed.