Mesoscale modelling and analysis of damage and fragmentation of concrete slab under contact detonation

It is interesting and important for researchers to understand the damage process in order to reliably predict fragment distribution of concrete material under blast loading. In the present study, a mesoscale concrete model is developed to simulate the dynamic failure process of a concrete slab under contact detonation. In the mesoscale model, the concrete material is assumed to consist of two phases, that is, the high strength coarse aggregates and the low strength mortar matrix, randomly distributed in the structure components. Each coarse aggregate is assumed to be circular with a random radius in a given distribution range following the Fuller's curve. The mesoscale model together with a dynamic plastic damage material model is incorporated into the hydrocode AUTODYN. The dynamic damage process of the concrete slab under contact detonation is numerically simulated. Based on the numerical results, the fragment size distribution is estimated by an image analysis program. Two different random aggregate distributions are assumed in the present simulations. Numerical results from the two different cases are compared, and the results from the mesoscale model are compared with that from the homogeneous concrete material model. The fragment size distributions obtained from numerical simulations are also compared with those from the empirical statistic formulae.