TECHNOLOGICAL FEATURES OF ULTRASOUND APPLICATION IN THE MANUFACTURE OF COMPOSITE STRUCTURES MADE OF PRE-PREGS WITH AN EXPIRED EPOXY

The prospects of using polymer composite materials (PCM) in the designs of various technical systems are shown. It is stated that despite the expanded use of thermoplastic polymers, there remains a tendency towards the predominant use of thermoplastic (in particular, epoxy) binders. This is due to the better impregnation of most fibers with these polymers, which ensures high-quality uniform impregnation of the filler using vacuum infusion technology. There is a serious shortage of epoxies with a limited expiration of pre-pregs which form the product, and the possibility of recycling PCMs made of them. This creates certain difficulties for the disposal of expired pre-pregs. A method is proposed and experimentally substantiated for processing such materials into highly filled layered composite plates by layering with ultra-sound. It is shown that controlled softening of the binder without its thermal destruction under the action of ultrasound and the creation of a certain pressure makes it possible to achieve the connection of the layers into a composite structure. Rational technological parameters are determined such as oscillation amplitude of 15-20 microns, static pressure of 0.16–0.19 MPa, temperature in the range of 80-90°C. It is found out that the samples obtained in these modes correspond in bending strength to the samples obtained using traditional pressing technology from suitable pre-pregs, and in the range of deformations of 0.3 mm or less, they even significantly exceed them. The research results can be used to solve the problem of utilization of pre-pregs based on expired epoxies by manufacturing products from them with reduced durability requirements, working mainly in the field of small deformations under the action of external loads.