Non-Destructive Radio Wave Scanning Method for the Inspection of Composite Materials

Polymer composites, for example, carbon or aramid fibre-reinforced plastics, are widely used in aviation technology, aircraft engines for the manufacture of load-bearing elements. The main advantage of composite materials based on synthetic reinforcing fibers is a high specific strength, the ability to control the strength and rigidity of a structure over a wide range, achieving its high weight perfection. A significant disadvantage of traditional layered composites is the low resistance to transversal impact. Low-velocity impacts are commonly occurred in the operation of aircraft structures: tool drops during maintenance, hail, gravel from the runway, bird strikes, etc. Intra- and interlaminar damages (delamination, fibre fracture) that occur during impacts significantly affect the residual strength of the composite element and can lead to its sudden failure during normal operation. In this regard, an important part of health monitoring of composite structures is the identification of impact defects for their further repair or the decision to replace the entire element. In this regard, it is of considerable interest to determine the location of a possible defect in a semi-automatic mode using remote control methods, in particular, radar and radio waves. The paper presents the results of state control for a sample of an aramid plate with defects, obtained microwave holograms in the frequency range of 15–24 GHz, and reconstructed microwave images in three-dimensional planes. The proposed method of non-destructive testing can be successfully used to determine damage in composite structures reinforced with glass and organic fibers, etc.