Clamped Beam Bending for Mixed Mode Fracture Toughness Measurements

Abstract

AbstractClamped beam bending geometry has been successfully used for evaluation of mode-I fracture toughness on micro and macro specimen (Jaya B, N., Jayaram, V. & Biswas, S. K.: A new method for fracture toughness determination of graded (Pt,Ni)Al bond coats by microbeam bend tests. Philos. Mag. 92, 3326–3345 (2012).; Mishra, A. K., Lambai, A., Jayaram, V. & Jaya, B. N.: The edge-notched clamped beam bend specimen as a fracture toughness test geometry. Theor. Appl. Fract. Mech. 105, 102,409 (2020) [1, 2]. The present study explores the utility of clamped beam bending for studying mixed mode fracture. Mode-I and mode-II stress intensity factor solutions are obtained by changing the position of the loading point with respect to the notch (offset), and of angular notches with respect to the loading axis. Mode-II stress intensity factor is computed as a function of the loading offset and relative crack length using the finite element method (FEM). FEM results show that clamped beam with offset loading point is able to provide pure mode I, pure mode II and any mixed mode loading condition for L/W = 4 with a/W = 0.5 to 0.7. Clamped beam with angled crack shows pure mode I and mixed mode but can’t provide pure mode II. Using this information, mixed mode fracture trajectory is predicted, which is relevant for the evaluation of fracture behavior of multilayered and composite structures.KeywordsMixed modeClamped beam bendingFEM