A mechanical particle model for analyzing rapid deformations and fracture in 3D fiber materials with ability to handle length effects

The model is applied to simulate and analyze crack growth in random fiber networks with varying density of fibers. The results obtained in fracture zone analyses show that for sufficiently sparse networks, it is not possible to make predictions based on continuous material assumptions on a macroscopic scale. The limit lies near the connectivity lc/L=0.1, where lc/L is the ratio between the average fiber segment length and the total fiber length. At ratios lc/L<0.1 the network become denser and at the limit lc/L→0, a continuous continuum is approached on the macroscopic level.