Purpose -The purpose of this paper is to address the problem of substitution of steel with fiberreinforced polymer-matrix composite in military-vehicle hull-floors, and identifies and quantifies the associated main benefits and shortcomings. Design/methodology/approach -The problem is investigated using a combined finite-element/ discrete-particle computational analysis. Within this analysis, soil (in which a landmine is buried), gaseous detonation products and air are modeled as assemblies of discrete, interacting particles while the hull-floor is treated as a Lagrangian-type continuum structure. Considerable effort has been invested in deriving the discrete-material properties from the available experimental data. Special attention has been given to the derivation of the contact properties since these, in the cases involving discrete particles, contain a majority of the information pertaining to the constitutive response of the associated materials. The potential ramifications associated with the aforementioned material substitution are investigated under a large number of mine-detonation scenarios involving physically realistic ranges of the landmine mass, its depth of burial in the soil, and the soil-surface/floor-plate distances. Findings -The results obtained clearly revealed both the benefits and the shortcomings associated with the examined material substitution, suggesting that they should be properly weighted in each specific case of hull-floor design. Originality/value -To the authors' knowledge, the present work is the first public-domain report of the findings concerning the complexity of steel substitution with composite-material in military-vehicle hull-floors.