Optimization of pressure and time of composite products molding at the temperature of minimum binder viscosity

Abstract

The technological process of composite products’ molding consists in giving them non-a reversible shape using shape-generating molding tools through polymerization of the binder at a certain temperature and pressure varying in time. The paper deals with the research of technological parameters of the most common practical method of molding products made of polymeric composite materials, pre-formed of prepregs. The mathematical model of filling with a binder of inter-fiber space of the reinforcing material for the polymeric composite material with the varying fiber packing densities, from quadratic to hexagonal one, depending on the type of reinforcing material, has been further developed. A new method for optimization of the pressure and time of composite products’ molding at the temperature of the minimum binder viscosity has been developed. The method is implemented by analytical dependencies, which establish the optimal time intervals and pressure of molding on the section of the temperature and time diagram, associated with the ability of the operating equipment (oven, autoclave) to provide the maximum possible rate of temperature rise in order to “soften” the binder in prepreg to its minimum viscosity. It is shown that energy consumption for the re-formation of the tetragonal structure of the polymeric composite material into hexagonal one is ten times higher than the costs for the tetragonal structure formation. For example, re-formation of the tetragonal structure at volume content of the binder of 0.4 into dense hexagonal structure requires 66.7 times increase in pressure. Obtained results allow establishing the economically feasible level of pressure and time of composite products’ molding while ensuring their specified quality.