Feasibility study on Hartman–Schijve data analysis for mode II fatigue fracture of adhesively bonded wood joints

Abstract

The feasibility of using the modified Hartman–Schijve (HS) equation to analyze the fatigue fracture performance of adhesively bonded wood specimens under cyclic mode II loading was investigated in comparison with the Paris crack growth equation. Wood joints prepared with three different adhesives have been subject to cyclic Mode II testing at room-temperature ($$23\,^{\circ }\hbox {C}$$ and 50% relative humidity) in a four-point End-Notched-Flexure configuration, determining the crack length from specimen compliance. It was shown, that the HS-equation can be successfully applied to adhesively bonded wood and that it successfully estimates threshold and maximum energy release rate (ERR) values for three different adhesive systems. Since a limited number of tests were performed for investigating the feasibility, scatter sources and possible scatter reduction methods are analyzed and discussed in detail. Also, a new, automated data reduction method was developed for estimating the maximum and the threshold ERR ($$\hbox {G}_{\mathrm{thr}})$$ values. The main advantage of the HS-equation appears to be the application in design standards. However, before the maximum ERR and $$\hbox {G}_{\mathrm{thr}}$$ values derived here can be used in design applications or for drafting a design guideline, additional testing is required for understanding how the number of cycles, the related measurement resolution; the corresponding ERR value influence the threshold value $$\hbox {G}_{\mathrm{thr}}$$ and how and to what extent its scatter can be reduced; and to further explore the link between cyclic ERR and the critical ERR value measured during quasi-static fracture tests.