A Study on the Mixed Mode I‐II Fracture Criterion of HMX‐Based Polymer Bonded Explosives

ABSTRACT Accurate assessment of fracture behavior and prediction of residual life are critical for understanding failure mechanisms in polymer‐bonded explosives (PBXs). In this study, semicircular bending (SCB) specimens of PBXs with varying crack lengths (4.0, 5.1, 6.4 mm) and different initial crack angles (0°, 15°, 30°, 45°, 60°) were designed to systematically study the fracture behavior of PBXs under complex loading conditions. Traditional forms and generalized forms (T‐stress corrections) of stress‐based, strain‐based, and energy‐based fracture criteria were employed to predict the fracture behavior, and the predictions were compared with experimental results to evaluate the applicability of each criterion to PBXs. The results demonstrate that traditional fracture criteria provide reliable predictions for PBXs fracture behavior when mode I fracture is dominant. However, when mode II fracture is dominant, the predictions of fracture behavior by traditional criteria exhibit significant discrepancies from experimental observations. In addition, the stress‐based and energy‐based fracture criteria, after incorporating T‐stress corrections, can effectively predict the fracture behavior of PBXs under mixed mode I‐II cracking, particularly the generalized minimum strain energy density factor criterion, which considers transverse deformation and energy dissipation, whose prediction results are almost consistent with the experimental test results. However, even with T‐stress corrections, the strain‐based fracture criterion still fails to accurately predict the fracture behavior of PBXs. The work of this paper can provide an important theoretical basis for evaluating the damage tolerance of PBXs structures under complex loading conditions.