Method of continuous non-destructive observation of profiles made of polymer fibre composite materials for the registration of crack formation

Abstract

The relevance of the study is conditioned by the absence of the necessary devices and structures made of composite materials such as stingers with holes for registering cracks. The purpose of the study is to develop the design and manufacturing technology of stringer-type profiles made of composite materials with micro-holes in the cross-section or inside which hollow polymer fibres are laid, while the holes did not significantly affect the strength of the product and the specified strength properties of the product are preserved. The task of manufacturing products from a polymer composite material is solved by a method that includes pre-laying hollow longitudinal fibres or introducing bundles coated with anti-adhesive lubricant at specified cross-section points of stringers with subsequent pressing when laying pre-cut layers of composite material in a mould (polymerisation of the binder). After cooling, decompressing, removing the bundles with anti-adhesive grease (the second option) and stripping the product, special sensors are installed, a vacuum is created inside the holes or pressure is applied within 0.1-0.2 atm. At the same time, the holes do not significantly affect the strength of the product and the specified properties of the product are preserved. The study suggests a method for continuous and autonomous monitoring of the integrity of profiles made of polymer fibre composite materials for registering the formation of cracks based on the introduction of longitudinal micro-holes or hollow fibres under pressure or vacuum into their structure, followed by recording changes in the pressure value. The advantage of the proposed method is that it allows making a product from composite materials with increased physical and mechanical properties, increasing operational safety, increasing service life, and reducing the cost of routine inspections due to continuous monitoring of the occurrence and development of damage in real time. At the same time, the reliability of the design significantly increases, which leads to an improvement in the quality of the product