With the Artemis program, NASA is returning to manned space flight and plans to send humans to the Moon and Mars in the decades to come. New space vehicles and systems are being developed and tested, and a significant percentage of the structures in these spacecraft will be composite materials. Composites offer high stiffness- and strength-to-weight ratios, but they also exhibit complex damage modes, including voids, delaminations, matrix cracking, fiber breakage, and combinations of all the above. This offers many challenges for ultrasonic nondestructive evaluation (NDE) and structural health monitoring (SHM).
A proper understanding of the physics of a given NDE/SHM method is critical for the meaningful characterization and quantitative assessment of structural health. A need therefore exists to fundamentally understand the interaction of interrogative ultrasonic wave energy with the complex fiber/matrix system and damage types in multi-layered composites. To address this issue, a predictive tool with quantitative computational NDE/SHM capabilities is necessary to the success of future space missions.
In this project, it is proposed to develop a physics-based software package to model ultrasonic energy interaction with composite damage in both the frequency and time domains. The software package utilizes open source code and a fast and efficient Distributed Point Source Method (DPSM) to solve frequency domain ultrasonic wave fields in multi-layered composite structures with and without damage. The objective of this effort is to expand the DPSM capabilities to obtain time domain sensor responses at any location. Parallel computing capability will be implemented to solve the problem at multiple frequencies such that the time domain signal can be computed at any point on the structure. The wave energy-material modeling software package will be an essential tool to optimize sensor locations and minimize the total number of sensors and weight of future NDE/SHM systems.
It is anticipated that the first application of the technology will be the integration into NASA’s digital NDE/SHM tools for large complex composite space structures, such as the Artemis program’s Orion crew module and Space Launch System. As NASA directs efforts into deep space flight, NDE/SHM systems will be needed to provide mission critical information about the structures. For these NDE/SHM systems to be viable, a computational tool, such as the proposed software package, to accurately model the energy-material interaction is essential.
Non-NASA applications include large, commercial space launch vehicles that utilize composite materials. The US Air Force, Army, and Navy also have a growing interest in simulated NDE with the concept of ‘Digital Twin’ and real time material state awareness. Generally, any industry that uses large composite structures that require frequent inspection will benefit from the technology.