The mechanical strength of agglomerate materials under impact has been investigated by means of computer simulation using Distinct Element Analysis (DEA). The effects of impact velocity and surface energy are addressed. The agglomerates show increasing extent of breakage with increasing impact velocity, but eventually reach a limit above which the damage approaches an asymptotic value. Particles held together by larger adhesive forces yield stronger agglomerates. This is largely related to the effect of the surface energy on the mechanical properties of the agglomerate, such as Young's modulus and fracture surface energy. Observations of particle breakage show no clear planar crack propagation, but rather the disintegration of the agglomerate from the impact site, propagating to the rear of the agglomerate. It is considered that the structure of the agglomerate, as influenced by the method of preparation, does not store sufficient strain energy to allow crack propagation.