Size Effect and R-Curve in Quasibrittle Fracture

Abstract

In solid mechanics, an essential scaling problem is the effect of the structure size on its nominal strength. This effect is particularly important in the case of quasibrittle materials which are characterized by the existence of a large Fracture Process Zone (FPZ) where various toughening mechanism take place such as microcracking, crack branching or crack bridging. Materials as different as concretes, mortar and rocks, some composites and wood belong to this category. From a classical equivalent linear elastic approach (where the increase of the specimen compliance due to the FPZ development is attributed to the propagation of an elastically equivalent crack [1],[2]) the fracture behaviour of quasibrittle materials is characterised by a more or less pronounced rising resistance curve, commonly called R-curve [3]. This R-curve behaviour emphasizes stress redistributions and stored energy release which take place in such large FPZ.