Mixed mode fracture energy of sprucewood

The characterization of Mixed Mode (Mode I and Mode II) behaviour of wood w as concentrated on concepts of linear fracture mechanics in the past. Using an adopted version of the splitting test it was possible to obtain complet e load displacement curves under different Mixed Mode loading cases for cra ck propagation along the grain. Therefore fracture energy concepts (specifi c fracture energy) could be used to characterize the material behaviour. Ad ditionally strength parameters were used in order to describe crack initati on in two crack propagation systems. The values for specific fracture energ ies as well as the strength values were compared with pure Mode I fracture tests. Moreover, the size effect under Mixed Mode loading was investigated to guarantee size independent material characterizing values for the specif ic fracture energies. (C) 2001 Kluwer Academic Publishers.