Low velocity impact damage assessment in IM7/977-3 cross-ply composites using 3D computed tomography

摘要

Low-velocity impact damage in IM7/977-3 carbon fiber reinforced polymer (CFRP) composites was investigated using 3D computed tomography (CT). 32-ply IM7/977-3 symmetric cross-ply composites were impacted at different impact energy levels and with different impactors (DELRIN® resin flat-ended cylindrical and tool steel hemispherical strikers) using an Instron 8200 Dynatup drop-weight impact machine. The impact energies were chosen to produce slightly visible damage, characterized by short cracks on the impacted surface and little delamination on the non-impacted surface (29.27 J), and barely visible damage, characterized by indentation on the impacted surface but no visible delamination on the back surface of the specimens (20.77 J). Internal damage was assessed using the Zeiss METROTOM 1500 industrial CT scanning system, and CT images were reconstructed using VGStudio MAX and the MyVGL 2.2 viewer. To determine the extent of the damage zone, impacted 152.4 mm square composite plates were initially scanned. As the relatively large specimen size did not allow for evaluation of internal cracks and isolation of delamination at ply interfaces, smaller specimens that enclosed the damaged region (45 mm square plates) were cut out and imaged. The CT scan results showed that volume of the impact damage zone had a generally positive correlation with impact energy, maximum load, and maximum deflection, but that the relationship was generally weak. Absence of a definite correlation between damage volume and impact energy was unexpected, as the difference in the impact energy was up to 30%.