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Hail ice impact on composite structures at glancing angles

Abstract

Aircraft structures are susceptible to damage due to high velocity hail ice impact. These impacts can create nonvisible damage in the structure, jeopardizing its structural integrity. Experiments were completed with simulated hail ice (SHI) impacting T800/3900-2 carbon/ epoxy tape laminates and aluminum panels at various angles. The angled impacts were similar to the normal impacts in the failure propagation of ice as well as the size and shape of the delaminations. Experimental failure threshold values were not in agreement with the trigonometric scaling of the failure threshold energy (FTE) or the failure threshold velocity (FTV) of normal impacts but seemed to be bounded by the two curves. Simulations in Abaqus/Explicit were created at the experimental failure threshold velocities (FTV) to study delaminations. Peak interlaminar shear stresses were found to be between 104 and 130 MPa. The peak interlaminar shear stress was a good indication of failure onset, while the Northwestern University (NU) and Hashin-Rotem failure criteria seem to require adjusted material properties for the higher strain rates. Dent depths in the composite panels were not indications of existing delaminations, and there was no correlation found between dent depth and delamination size. Impacts on the aluminum panels with similar energies created dent depths that were an order of magnitude higher than the composite panels and thus clearly more visibly detectable

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