Acoustic emission technique for fracture analysis in wood materials

Understanding the failure mechanisms of construction materials, as well as their damage evolution, constitute two key factors to improving structural design tools. Depending on the failure modes to be highlighted and studied, several test methods and analysis tools have been developed. One such development, the acoustic emission technique (AET), is an experimental tool appropriate for characterizing material behavior by means of monitoring the fracture process. Despite the widespread uses of acoustic emission techniques to characterize and monitor the damage evolution of composite materials, only a few research studies have focused on using AET to characterize the mechanical behavior of wood materials. In the present work, the failure process in Douglas fir under monotonic loading is studied by comparing three experimental methods: force-displacement curve analysis, acoustic emission measurements, and digital image acquisition. First of all, results show good correlation and complementarities among the methods employed. Second, analyzing acoustic emission signals by considering the event number and the cumulative events yields interesting information on crack initiation and growth without the material. Moreover, an additional analysis of acoustic emission data (involving the determination of source locations and the study of amplitude distributions) opens the possibility to characterize the fracture process zone which is a key damage mechanism in wood materials.