Mechanical properties and optical testing of metal honeycomb sandwich panel in MTPS

Mechanical tests of a Co-based superalloy honeycomb thermal protection system (TPS) panel are finished at room temperature. The lateral tensile limit strength is higher than 59MPa and nearly four multiples of the flatwise compressive strength. Also the modulus in lateral tests are nearly two multiples of the ones under compressive loads. Because of many advantages in application, two optical non-contact methods are introduced in this work to solve different problems of honeycomb sandwich panels. Longitudinal strain of lateral tensile specimens is obtained by digital speckle correlation method (DSCM) and the results of different sub-pixel methods are constrasted. Then the equivalent elastic modulus is calculated further. Electronic speckle shearography pattern interferometry (ESSPI) is presented to obtain the nondestructive results of debonding defects between honeycomb cores and face sheets. Also the size and approximate location are decided real-time. All the results show the two introduced methods are feasible.