Damage Detection of Textile Composite Structures Using the Piezoelectric Impedance Method

Abstract

Structural health monitoring of aerospace structures is becoming vital as lightweight composite materials are increasingly used in aero-structures. Composites have various types of failure modes, which make it even more important to identify damage compared to isotropic materials. Therefore, on-site health monitoring is one of the most preferred methodologies for detecting internal crack or damage at its initial stage to enhance operating safety and reduce repair cost. Recently, piezoelectric transducers are on high demand for on-site health monitoring because of its high bandwidth sensitivity. They simultaneously perform as actuators and sensors and embedded on the structure. The electrical impedance or admittance changes according to modification in mass, stiffness or damping properties of the host body. In this study, plain-weave textile composites are utilized to demonstrate capability of piezoelectric transducer. The elastic properties of composite are determined using the Concentric Cylinder Assemblage micromechanics model. Finite element modeling is done in ANSYS APDL to observe electrical admittance variation around natural frequency. Delamination and intra-ply damage cases are studied. Delamination is separation of adjacent plies and damage is reduction of stiffness in the whole structure. Modal frequency of the structure decreased with delamination and damage level increment within the body. Pre-preg manufacturing method is carried out to fabricate composite panel from which samples are cut for testing according to ASTM standards. Piezoelectric test provided voltage drop across the resistor that denoted the coupling effect of the patch with the host structure. Electrical admittance plot expressed response to body deformation actuated by the piezoelectric transducer. Results from finite element modeling and experimentation assert that piezoelectric impedance technique is efficient in detecting damage or delamination within the composite structure.