CHEN Liang ^{1, 2}, MENG Linshu ^{1, 2}, ZHANG Yinxuan ¹, WANG Guangshuai ¹, CAO Qikai ¹,
ZHAO Mingzhuo ³, WU Tao ^{3, 4}, GAO Xiguang ^{3, 4}, SONG Yingdong ^{3, 4, 5}
(1. Shenyang Aircraft Design & Research Institute, The Aviation Industry Corporation of China, Shenyang, 110035, Liaoning, China; 2. Dalian University of Technology, Dalian 116024, Liaoning, China; 3. Nanjing University of Aeronautics & Astronautics, Nanjing 210016, Jiangsu, China; 4. Jiangsu Province Key Laboratory of Aerospace Power System, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, Jiangsu, China; 5. State Key Laboratory of Mechanics and Control Mechanical Structures, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, Jiangsu, China)

Extended Abstract: [Background and purpose] Ceramic Matrix Composites (CMCs) represent an emerging class of materials characterized by their low density and exceptional thermal stability. They have attracted significant attention in recent years due to their remarkable performance in high-temperature environments, making them ideal candidates for use in advanced thermal structural applications. The development of CMCs is particularly notable in high-thrust-to-weight ratio aerospace engines, detonation engines, and integrated materials for thermal protection structures, where their unique properties, such as high strength-to-weight ratio, high-temperature resistance, and excellent damage tolerance, are crucial. These composites offer vast potential for improving the performance of aerospace and defense technologies, especially in scenarios where conventional materials fail to meet the stringent operational demands. However, traditional methods for testing the performance of materials, such as validation through physical tests, are inherently time-consuming, costly and not always suitable for rapid material development and research. Such approaches often require extensive trials and can be limited by the pace of technological advancements. In light of these challenges, the development of more efficient and scientifically robust material performance testing and simulation techniques has become a central focus in CMCs research. These methods not only aim to reduce the cost and time involved in material testing but also enable more accurate predictions of material behavior, which are essential for guiding the design and optimization of next-generation CMC structures.[Methods] Experimental and simulation-based approaches were integrated to better understand the material’s behavior under different loading and environmental conditions. The experimental part includes tensile, compression and bending tests for the 0° layer and woven layer materials of 2.5D needled C/SiC composites, at room temperature, 500 ℃ and 1000 ℃, in an oxygen-free environment. In addition to the mechanical testing, electron microscopy was employed to observe and analyze the fracture surfaces of the tested samples. This allowed for a detailed investigation of the material’s failure modes and damage evolution, providing valuable insights into the specific damage mechanisms at different temperatures.  [Results] It is found that the failure modes of the 2.5D needled C/SiC composites varied significantly with temperature, revealing the complex interplay between thermal effects and mechanical stresses. Understanding these failure modes is critical for the development of more reliable and durable CMC materials that can perform well in extreme conditions. Based on the experimental data, a method was proposed for obtaining the macroscopic mechanical properties of needled elements using the performance parameters of a single ply. This method is based on the assumption that the mechanical properties of the composite materials can be inferred from the behavior of individual layers, thereby simplifying the analysis of the overall material system. Also, multi-scale theory and progressive damage methods were incorporated to simulate the mechanical behavior of the CMCs at different scales. These methods allowed for a more accurate representation of the material’s complex internal structure and the interactions between the individual components. To carry out the simulation, a secondary development of the Abaqus subroutine was employed. This involved creating a detailed numerical model of the 2.5D needled C/SiC composite material that could capture the material's micromechanical properties and predict the macroscopic mechanical response. In the model, a Representative Volume Element (RVE) was utilized, which is a small representative sample of the material that encapsulates the microstructure. This approach allows for the simulation of the material's behavior under different loading conditions, making it possible to predict the strength and failure modes under various environmental conditions.[Conclusions] The successful simulation of the strength and failure modes of 2.5D needled C/SiC composites at both room temperature and high temperatures demonstrated the potential of computational models for the design and optimization of advanced CMC materials. The simulation results were in good agreement with the experimental data, confirming the accuracy and reliability of the proposed modeling approach. The stress distribution and failure modes predicted by the simulation were found to well match the experimental observations, demonstrating the effectiveness of the simulation methodology in capturing the material's response at different mechanical loads. Furthermore, the strength prediction accuracy, based on the maximum strain criterion, was found to be 94.7%, strongly evidencing the validity of the simulation model.
Key words: C/SiC composites; multiscale analysis; performance prediction; failure analysis