Damage Detection in Cryogenic Composites for Space Applications Using Piezoelectric Wafer Active Sensors

Abstract : Lamb waves have proven to be effective for damage detection by passively listening for emitted signals from crack growth or actively interrogating the structure. Acoustic emission sensors are used for monitoring a wide number of defects in materials such as dynamic strain, crack growth, leakage, corrosion, delamination, and fiber breakage in composite structures. The present paper will present an extensive experimental evaluation of the structural health monitoring (SHM) capability of the PWAS on composite structures of different geometries, environmental conditions, and stress conditions. Results from these experiments indicate that a PWAS based array is capable of detecting low velocity impact damage in composite materials. These experiments showed that abrupt changes in the DI occurred for sensor paths near the impact damage sites, which also indicates that localization of the damage is feasible using PWAS based arrays for SHM. The robustness of the PWAS arrays is demonstrated for damage detection at ambient, cryogenic, and cryogenic temperatures under uniaxial loading using both pulse-echo and pitch-catch methods. Based on these results, a PWAS based SHM array is shown to be a promising method for impact damage detection in composite materials, even in extreme conditions.