Experimental determination of R curves for European spruce using DCB tests

Abstract

This paper presents an experimental procedure for obtaining the fracture resistance (R curve) of solid wood specimens made of spruce. Double Cantilever Beam (DCB) tests were performed in order to determine energy release rate vs crack length in Mode I wood fracture (crack opening). Ten wood specimens were loaded using the Universal Testing Machine and force-displacement curves were recorded. The most important parameter - crack length was monitored as the crack propagates using Digital Image Correlation (DIC) method. In order to obtain accurate R curve results, procedure which includes calculating cumulative released energy was employed. The cohesive energy Gf was determined based on the R curves. These results can further be analysed in order to obtain cohesive law for Mode I fracture of wood.