Hi,

I have completed my master's aeronautical engineering. My theisis was on ndt of composite structures using ultrasonic air coupled c scans. I completed my masters 2 years back. Now i want to pursue my Phd. I want to do in the area of composites itself and related to aircraft structures. Can someone help me to know what basic subjects should i study to go before an interview and with what subjects i can build my basics. Can someone please help me recognizing research areas also ?

It depends on the area of research. In aircraft structures, mostly CFRP composites are used (if I am not wrong). So I would recommend you to read basics about these composites, such as mechanism of failure modes for these composites, different materials used and so on.
However, I would suggest you to prepare for the interview based on research activities defined for that particular research. Good luck