Acoustic Emissions and the Fracture Energy of Wood

Recent advances in engineered wood composites are allowing us to further push the load limits of timber used in structural applications. In an effort to better understand failure processes we are applying acoustic emission techniques to examine progressive crack growth along the grain in clear wood specimens loaded for mode I fracture. We have developed a technique to estimate the energy released by an acoustic event. By applying basic fracture theory we can determine the bulk fracture energy of the specimen from load versus crack length data. A comparison of acoustic energy measurements with bulk fracture energy measurements gives us an idea of how much fracture energy is converted to acoustic energy. Results from the experiments presented here indicate roughly one sixth of the fracture energy is measured as acoustic emission energy. This comparison will allow us to apply the technique to laboratory tests of damage growth in larger structures.