Microwave Nondestructive Testing of Galvanic Corrosion and Impact Damage in Carbon Fiber Reinforced Polymer Composites

Advanced composite materials are being used extensively in many commercial and military aircraft and rotorcraft due to their superior stiffness and high strength-to-weight ratio. These composites are subjected to unexpected environmentally assisted damages. This work covers exploration and the methodology of detection of two such types of damages - galvanic corrosion and impact damages, at the earliest stages of development.

When aluminum alloy and CFRP are coupled together, the structural strength of the aircraft is unparalleled, but this comes at a price, namely galvanic corrosion (GC). Previous experimental results have shown that when CFRP composite materials are joined with high strength aluminum alloys, galvanic corrosion occurs at the material interfaces, and the aluminum is in great danger of corroding.

Composite materials used in aircraft are often subjected to unexpected environmental impact loads at high speeds, such as bird strikes and hailstone impacts. The damages developed in such cases is primarily in the form of delamination and matrix cracking, known as barely visible impact damage (BVID), since they are not easily observable by the naked eye. Prediction and detection of such environmental damages, which can occur in the service life of the aircraft, are of paramount importance in the aerospace industry.

This work utilizes the software BEASY for the prediction of galvanic corrosion and utilizes ABAQUS Explicit for modeling the bird impact damage and the hailstone impact damage by using the smoothed particle hydrodynamics (SPH) modeling method. This work also proposes a non-invasive microwave nondestructive testing (NDT) technique that can be employed as a detection methodology to detect the aforementioned types of environmentally assisted damages. Radar signals operating at a set frequency range can be used to detect the aforementioned environmentally assisted damages to obtain high-resolution 2D images of such damages.