Nondestructive evaluation of interlaminar bonding for in situ consolidation of polymer composites

A sensor for detecting poor interlaminar bonding between a topmost ply and composite substrate was developed and validated. The sensor was designed fo r the specific application of real time process control for in situ consoli dation processes, such as thermoplastic tow placement. The sensor design co nsists of two piezoelectric transducers oriented in a pitch catch arrangeme nt. The transmitting transducer is angled so as to produce surface waves in the composite panel. These waves interact with defects at the top ply/subs trate interface. The received signal was analyzed for wave speed, attenuati on and energy dissipation (power spectral density). Experimental validation of the sensor is presented. Several composite panels were made under vario us manufacturing conditions so as to create poor interlaminar bonding at th e topmost ply. Interlaminar bonding was then evaluated by destructive and n ondestructive measures. There was good agreement between the destructive an d nondestructive measures of top ply bond strength.