An experimental investigation on damage mechanisms of thick hybrid composite structures under flexural loading using multi-instrument measurements

In this study, damage characterization of thick carbon/glass fiber reinforced hybrid composites is performed under flexural loading conditions via two non-destructive evaluation (NDE) techniques, i.e., digital image correlation (DIC) and acoustic emission (AE). Experimental results demonstrate that the flexural modulus of the hybrid composites is strongly correlated with the location of carbon fiber plies; the closer these plies are to the laminate faces, the higher is the modulus. On the other hand, the flexural strength depends on the type and extent of damage initiation in the laminates. Interply hybridization of carbon fiber reinforced composites (CFRPs) with glass fiber not only improves their flexural strength and failure strain but also facilitates failure predictability in CFRPs. The transverse and shear strains associated with various failure modes in thick hybrid laminates are efficiently captured by the DIC technique. In addition, AE results reveal that the strain levels associated with the onset of acoustic activity are linked to failure in the carbon fiber plies of the hybrid laminates. Furthermore, these observations made by DIC and AE on thick hybrid laminates are confirmed with optical fractography. Finally, it is revealed that ply lay-up sequence and laminate thickness notably alter both the mechanical performance and damage mechanisms of hybrid composites. (C) 2021 Elsevier Masson SAS. All rights reserved.