Development of the simple dielectric sensor for the cure monitoring of the high temperature composites

As fiber reinforced composite materials are widely used in aircraft, space structures and robot arms, the on-line cure monitoring during the cure process of the composite materials has become an important research area for the better quality and productivity. In this paper, the dielectric circuit of the Wheatstone bridge type for measuring the dissipation factor during cure of thermosetting resin matrix composite materials was designed and manufactured. Also, the dielectric sensor for the cure monitoring of high temperature composites was developed and tested. The residual thermal stresses of the dielectric sensor during cure were analyzed by the finite element method and its dielectric characteristics at high temperature were evaluated. The on-line cure monitoring of the Bismaleimide (BMI) resin was performed using the developed Wheatstone bridge type circuit and the high temperature dielectric sensor.