Modeling and simulation of environmental impact damage of aerospace composites and its detection scheme

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 composite materials are subjected to unexpected environmental impact loads at high speeds, such as bird strikes and hail stone impacts. The damages developed in such cases is primarily in the form of delaminations and matrix cracking, known as barely visible impact damage (BVID), since they are not easily observable by the naked eye. These environmental impact damages can severely compromise the overall strength of the composite structure thereby reducing the maximum load it can withstand. Prediction of such environmental impact damages, which can occur in the service life of the aircraft, are of paramount importance in the aerospace industry. This paper demonstrates the use of the smoothed particle hydrodynamics (SPH) modeling method to simulate the extreme deformation of the impactor (hailstone and bird) along with the composite plate. Since the physical testing of the aforementioned impact scenarios is extremely expensive and time consuming, the SPH modeling approach can be used as a co st - e f fe c t iv e t oo l i n t he d es ign of composite structures. This paper presents the results of simulated hailstone impact and bird impact occurring on an 8-layer unidirectional carbon fiber reinforced polymer (CFRP) plate. This paper also proposes a non-invasive microwave non-destructive testing (NDT) technique that could be employed as a detection methodology to detect the simulated impact damages. Radar signals operating in the X-band microwave frequency range (8-12 GHz) could be used to detect the delaminations occurring in between the layers of the unidirectional CFRP plate to obtain high-resolution 2D images of the impact damages.