Investigation of crack paths in natural fibre-reinforced composites

摘要

Nowadays, fibre-reinforced composite materials are widely used in many fields, e.g. automotive andaerospace. Natural fibres such as flax and hemp provide good density specific mechanical properties.Additionally, the embodied production energy in natural fibres is much smaller than in synthetic ones. Withinthis paper the fracture mechanical behaviour of flax fibre-reinforced composites is discussed. Especially, thispaper focuses on the determination and investigation of crack paths in compact tension specimens with threedifferent fibre directions under a static as well as fatigue load. Differences and similarities in the obtained crackpaths under different loading conditions are presented. Due to the pronounced orthotropic behaviour of thosematerials the crack path is not only governed by the stress state, but practically determined by the fibre directionand fibre volume fraction. Therefore, the well-known stress intensity factor solutions for the standardspecimens are not applicable. It is necessary to carry out extensive numerical simulations to evaluate the stressintensity factor evolution along the growing crack in order to be able to determine fatigue crack growth ratecurves. Those numerical crack growth simulations are performed with the three-dimensional crack simulationprogram ADAPCRACK3D to gain energy release rates and in addition stress intensity factors.