Nondestructive Measurements of Shear Modulus in a Sheet Plane upon Aging of Polymeric Composites

The potentialities have been studied of using a method for square plate torsion to determine the shear modulus in the plane of a sheet as a sensitive parameter for the aging of polymeric composite materials. The advantage of the method consists in the fact that one can perform the repeated measurements of mechanical parameters without destroying the sample. To substantiate the method, a cycle of drying and humidification of VPS-48 grade fiberglass plates and KMKU-3M, VKU-39, and VKU-45 grade carbon plastics has been performed after 7 years of full-scale holding in a moderately warm climate. The fact that the shear modulus in the sheet plane depends on the moisture content of materials in the course of their humidification and drying has been revealed. It has been proven that the method of square plate torsion can provide a high level of accuracy for measuring the value of this parameter.