Bondline Temperature Control for Joining Composites With an Embedded Heater

This paper applies estimation and control techniques to achieve the desired bondline temperature for out-of-autoclave, adhesive bonding of carbon-fiber composite components. Rather than heating the entire system to cure the adhesive, e.g., in an autoclave, this research uses controlled heating targeted at the bondline with an embedded heater. The main contribution of this work is control using estimates of the bondline temperature without embedded sensors and wiring (of materials not intrinsic to the system) that can lead to reduced bond strength. Sensors placed outside the bond region are used to accurately estimate the bondline temperature to within 2% of the temperature range over which the bondline temperature is changed. Experimental results show that the estimated temperature can be used with feedback to achieve the desired, bondline, time–temperature profile that is needed to cure the adhesive. Additionally, shear lap joint tensile tests show that the resulting joint strength is comparable to specimens bonded using an external heat blanket.