Comparing various toughening mechanisms occurred in nanomodified laminates under impact loading

Delamination is the most frequent failure mode in thermoset-based composite laminates which can be easily occurred under an impact loading. Applying nanofibers between composite layers is one of the attractive methods to decrease the influence of this phenomenon (delamination) on the operation of an engineering structure. In this study, various nanofibers were utilized to consider their effects on impact response of glass/epoxy laminates. The nanofibers were made of PA66, PCL, and their mixture (PA66/PCL) which their toughening mechanisms are different. The results showed that PA66 and PA66/PCL had the best effectiveness on damaged area caused by the impactor (reduction of 60%). According to these results and some other evidences, it is concluded that bridging between composite layers which was established by PA66 nanofibers is the best mechanism for toughening laminates. On the other hand, depending on the curing cycle, PCL can toughen the composite laminates with two various mechanisms: 1- bridging between the layers 2- phase separation. The evidences show that the first mechanism is much more effective than the second one.