Effect of Heating Conditions during Moulding on Residual Stress-Strain Behaviour of a Composite Panel

Currently, we observe extensive use of products made of polymeric composite materials in various industries. These materials are being increasingly used to manufacture large-sized structural parts that bear significant loads. However, increase in the volume of composites used in critical structures is impeded by the instability of properties of the resulting products. In most cases, the reason for this is the residual thermal stress-strain behaviour of the composite structure. This paper deals with the development of a method to predict the residual stress-strain behaviour depending on the heating conditions and distribution of the temperature field over the thickness of the moulded composite package. The method establishes the relationship between moulding process parameters and the effect of the auxiliary and basic equipment on the distribution of the temperature field, stresses, and strains in the moulded product. It is shown that the rate of temperature change at the stage of heating has its effect on the amount of residual deformation of the structure. Experimental studies have been carried out to determine the influence of several factors (rates of heating and cooling) on the residual deflection of the composite panel. Experimental data proves that specimens moulded under conditions of an increased heating rate get a greater deflection than those moulded at a lower heating rate. The error of results during the full-scale experiment did not exceed 6.8%. Our results provide an opportunity to determine the residual thermal stress-strain behaviour of the moulded structure with the required degree of accuracy without a series of experiments. It allows us to significantly simplify the practical implementation of the developed method and avoid any additional production costs.