Hierarchical Toughening and Self-Diagnostic Interleave for Composite Laminates Manufactured from Industrial Carbon Nanotube Masterbatch

In this research, a nanoscale modification with industrially available carbon nanotubes (CNT) masterbatch is explored to solve the problem of delamination and perform self-diagnostic and in-situ damage sensing and monitoring in composite laminates. Compared to other methods of introducing CNTs into laminate, the application of industrially available masterbatch is scalable, so that it is useful for large composite structures. The interleave is produced by painting the diluted masterbatch on the glass fiber prepregs. Two types of CNTs interleaves with a CNTs content of 0.6 wt% and 7.5 wt% were produced. The 0.6 wt% interleave has a detrimental effect of similar to 80% on Mode I initiation and propagation fracture toughness whereas, the 7.5 wt% interleave shows an improvement of 27% in initiation and 0.5% in propagation Mode I fracture toughness. The addition of CNTs interleaves turns unconductive laminate into a conductive laminate and hence, it was used for self-diagnostics of damage, targeting structural health monitoring applications. In-situ damage sensing and monitoring tests were performed by simultaneously measuring the resistance of the sample during the double cantilever beam test. The fractography of the interleaved composite laminates is studied and the hierarchical toughening mechanisms are identified and discussed.