Numerical modelling of thermal fields in a polymer composite
Polymer composite materials (PCM), having reinforcing glass fibers in their content and named glass-fiber-reinforced plastics (GFRP), are the most widespread composites applied in the industry. Due to their high strength and stiffness at low specific mass, the PCM more and more widely employed in aircraft building and space industry, superseding conventional metal alloys. One of the glass-reinforced plastics machining specifics compared to metal materials consists in different heat balance ratio, since up to 90% of heat released while cutting transfers into the tool, whereas up to 70% of heat goes to the chippings while cutting metall. In the especially loaded structures under study from polymer composite, the reinforcing packs from titanium foil placed between the reinforcing glass-fiber tape layers are used. This layered material of the “glass plastic - titanium” type is employed in manufacturing spars of the main and tail rotors of MI-28 and MI-35 helicopters. MS 6530 infrared pyrometer is used for the temperature control in the cutting zone. Maximum acceptable temperature of the machined sample, which does not cause PCM thermal defects formation, is determined by the differential scanning calorimetry (DSC). The DSC 200 F3 Maia equipment of the NETZSCH Company was employed. Finite element modelling was performed with COMSOL Multiphysics CAE system. Pyrometric data on average temperature registering in the cutting area allowed performing finite element modeling of thermal processes while a multilayer fiberglass plastic drilling, as well as revealing the sources and direction of heat flows. Mathematical model realized with the COMSOL Multiphysics software allowed revealing space-time regularities of temperature fields’ proliferation and values of critical temperatures inside the composite. Cutting temperature rise in the process of titanium foil layers cutting leads to the composite layers warming up, which degrades polymeric matrix properties and intensifying thermal defects formation. Finite element modelling allowed upgrading technology of fiberglass spars of the helicopter main and tail rotors machining.