Advances seen in high-temperature ceramic matric composites and in hypervelocity impact test facilities
By Emily Arnold and Craig Merrett|December 2024
The Structures Technical Committee works on the development and application of theory, experiment and operation in the design of aerospace structures.
In June, researchers at Mississippi State University with FAA and NASA’s Langley Research Center in Virginia concluded a study of carbon composite T-joints. These structural elements connect adjacent structural parts, such as wing skins to stiffeners, thereby providing the load path between structural components. Researchers fabricated and tested stitched Vacuum-Assisted Resin Transfer Molding resin-infused T-joints under pull-off conditions. Results indicated a 15% increase in ultimate load and an approximately 58% increase in energy absorption. The researchers demonstrated that through-thickness stitching significantly improves the damage tolerance of T-joints, highlighting the effectiveness of stitching in enhancing the structural integrity of large aerospace components.
Texas A&M University’s Hypervelocity Impact Laboratory provides a high-throughput test bed for development and characterization of novel materials and structures subjected to normal and oblique HVIs over a range of velocities (0.1-8.0 kilometers per second), temperatures (minus 140 300 degrees Celsius), and pressures (5-760 Torr). Between December 2023 and June, Texas A&M researchers launched single projectiles and distributed particles via a coupled 12.7-millimeter bore single- and two-stage light gas gun to study applications in force protection, counter-hypersonics, micrometeoroid orbital debris impact mitigation and planetary defense. Ultra-high-speed in-situ diagnostics included laser velocimetry, shadowgraphy, particle/fragmentation tracking, Schlieren imaging, in-line holography and flash X-ray radiography. Aerosolized particles, including water and dust, introduced into the path of the incoming projectiles were used to assess shock-shock and particle-shock interactions. Results from this research are contributing to the development of the 1-km-long Ballistic, Aero-Optics, and Materials Range under construction at Texas A&M, as well as a 101.6-mm-bore single- and two-stage light gas gun.
Arizona State University continued developing a validated computational framework for modeling the nonlinear, time-dependent behavior of ceramic matrix composites, CMCs, at high temperatures and under sustained loading. In February, researchers created a deep learning-based framework to capture microstructure features and variability in CMCs with a silicon carbide-based matrix. Researchers use these microstructures in formulating a coupled creep-damage micromechanics model to capture complex load-sharing mechanisms. In June, they developed a multiphysics methodology and numerical scheme for modeling the multiregime oxidative response of CMCs, accounting for interactions between oxygen diffusion, matrix cracking, oxidation and stress at the microstructural scale. The team, in collaboration with RTX Technology Research Center in Connecticut, completed surrogate models for integration into CMC lifting codes using physics-constrained deep learning frameworks in November. Funded by the U.S. Department of Energy and the Army Research Office, this research will impact aircraft engines and land-based turbines that use CMCs by improving component reliability and failure prediction.
Composite materials with high strength-to-weight and stiffness-to-weight ratios are necessities for the aircraft industry. While these composites are already lightweight, reducing their weight further could improve aircraft performance and lower costs. One way to achieve this is through post-buckling design, although it comes with its own set of challenges, such as the identification of initial and progressive damage or failure modes after buckling. Preliminary Abaqus analysis completed in June by Lockheed Martin showed that by accounting for the impact of damage events on composite hat-stiffened panels as the weight changes under compression and shear loading, it’s possible to reduce structural weight up to 16% without damage at loads higher than the critical buckling load.
Contributors: Aditi Chattopadhyay, Vijay Goyal, Thomas Lacy and Rani Sullivan
