PREDICTION OF TEMPERATURE AND DEGREE OF CURE VARIATIONS IN CARBON FIBER COMPOSITE PANELS CURED IN A SINGLE-MAGNETRON MICROWAVE

Microwave heating and curing of carbon fiber reinforced composites offers several main advantages over autoclave curing, including direct heating of the composite, lower upfront and operation costs, and faster cycle times. With these advantages, however, also come several disadvantages such as incompatibility with metallic tooling, arcing of exposed carbon fibers, and a heterogenous electrical field within the microwave cavity and on the panel itself. The latter of which is the subject of this work. The heterogeneity of the electric field leads to areas on the composite panel with more intense and less intense heating effects due to stronger and weaker local electric fields, respectively. Another complicating factor in this study is the anisotropy of fiber reinforced composites, which have an electrically conductive portion (the fibers) and a much less electrically conductive portion (the polymer matrix). The electric field interacts with these constitutive elements differently, leading to different heating mechanisms. The fiber orientation in relation to the electric field is also a consideration for how far into the panel the electrical energy penetrates, which affects the heating and curing progression as well. In this work, these interactions are investigated using COMSOL Multiphysics finite element software to solve for electromagnetic, thermal, and curing physics. The differences for power needed to cure the two stack-ups are quantified as is the maximum temperature differences that the panels experience through their thickness and across their surfaces. This ensures that the panels are evenly cured and do not have areas where the temperature was high enough to degrade the matrix as other areas finished curing. These simulation results are compared to measured temperature data throughout the cure cycle.