SYSTEM OF AUTOMATED ACOUSTIC CONTROL OF PRODUCTS MADE OF POLYMER COMPOSITE MATERIALS

Abstract

The use of glued layered and honeycomb structures in aircraft construction can significantly increase the weight efficiency of technology, ensure its acoustic strength and high reliability [1]. Virtually the entire fuselage of the Boeing 767-300 is a multi-layer glued structure. A large number of various cellular units with metal (Al-alloy, Ti- alloy, steel) and non-metallic (from polymer composites) cladding and metal (Al-alloy) and non-metallic (from fiberglass, fiberglass, polyamide paper type "Nomex" and others.) honeycombs used on this and other aircraft. Thus, the area of glued structures on the plane is approximately 250 m2. In this regard, the requirements for quality control of glued structures and, above all, for their reliability are increasing. The internal structure of the products is alternate layers of fiberglass with different winding angles impregnated with epoxy compound. With acoustic non-destructive testing, the heterogeneity of the structure and the instability of the technology cause the acoustic signal level to vary from product to product by up to 15dB. A large attenuation coefficient (up to 10-15 dB/cm at a frequency of 300 kHz in multilayer products made of fiberglass) forces the use of low-frequency piezoelectric transducers, and the complex and heterogeneous shape of the surface - the implementation of the automation process in a contactless version. The use of the echo method at low (up to 500 kHz) frequencies does not allow accurate measurement of the depth of the defect due to the spread of the speed of the ultrasound signal through the thickness of the product. This forces us to look for additional ways to increase the accuracy of determining the location of defects, which are delamination of the material between the winding layers. This work considers the possibility of using automated acoustic control of PCM products, which allows detecting defects on the basis without a reference setting of the signal threshold value, detecting and identifying defects by the depth of occurrence in the process of automated control, and evaluating the stability of the product manufacturing technology based on the control resultsThe article presents the modeling of an automated system of acoustic impedance non-destructive testing, which from a practical point of view will provide an opportunity to control the stability of the technological process of forming a composite material and, if necessary, make its adjustments. The advantages of creating a system of automated acoustic control will allow registration of scanning and control conditions in an expanded form of C-scan in the process of non-destructive control and improve the process of documentation of results and decision-making regarding product evaluation for normality or defect.