The effect of matrix cracking on hysteresis behavior of cross-ply ceramic matrix composites is investigated in the present analysis. The cracking of cross-ply ceramic composites was classified into five modes, where cracking mode 3 and mode 5 involve matrix cracking and fiber/matrix interface debonding in 0° ply. The matrix crack space and interface debonded length are obtained by matrix statistical cracking model and fracture mechanics interface debonding criterion. Based on the damage mechanisms of fiber sliding relative to matrix in the interface debonded region, the unloading interface reverse slip length and reloading interface new slip length of cracking mode 3 and mode 5 are determined by the fracture mechanics approach. The hysteresis loops of four different cases for cracking mode 3 and mode 5 are derived respectively. The hysteresis loss energy as a function of interface shear stress of mode 3 and mode 5 are analyzed. The theoretical results have been compared with experimental data of two different cross-ply ceramic composites.

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To obtain some basic laws for bird-strike resistance of composite materials in aeronautical application, the high-velocity impact behaviors of composite laminates with different materials were studied by numerical methods. The smoothed particle hydrodynamics (SPH) and finite element method (FEM) coupling models were validated from various perspectives, and the numerical results were comparatively investigated. Results show that the different composite materials have relatively little effect on projectile deformations during the bird impact. However, the impact-damage distributions can be significantly different for different composite materials. The strength parameters and fracture energy parameters play different roles in different damage modes. Lastly, modal frequency was tentatively used to explain the damage behavior of the composite laminates, for it can manifest the mass and stiffness characteristics of a dynamic structure. The dynamic properties and strength properties jointly determine the impact-damage resistance of composite laminates under bird strike. Future optimization study can be considered from these two aspects.

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Competing failures are time domain contention situations between the propagated failures (PFs) that originate from dependent components and the failure isolation caused by the trigger component. The methods based on combinatorial analysis commonly used in the analysis of competing failures require a complicated formula derivation and model reduction process. This paper proposes an integrated model based on generalized stochastic Petri nets (GSPNs) for analyzing the competing failures in the system, and further considers the effect of common cause failures (CCFs). The proposed modeling method inherits the advantages of GSPNs and provides a simplified method to compute the reliability of systems, which affect by competing failures and CCFs. Finally, the proposed method is applied in the flight control system (FCS) and demonstrated by the efficient decomposition and aggregation (EDA) method and combinatorial analysis method.