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The micromechanical damage of a composite solid propellant was observed by in situ scanning electron microscopy. Based on the damage characteristics, a cohesive interfacial element was adopted to model the debonding processes along the particles and the binder interface. The effects of interfacial strength and microcracks in the binder on the debonding process of propellant were also examined. The results show that interfacial debonding is the propellant's main failure mode under tension. Finite element method analyses with a cohesive interfacial element could predict the heterogeneous strain and stress fields as well as the processes of the particles separated from the binder. Interfacial strength plays a significant role in macroscopic behaviors of the propellant. Microcracks in the binder significantly influence the debonding process. The numerical simulation results reasonably reflect the corresponding experimental results. These results provide the basis for the prediction of mechanical properties and the optimal design of the composite solid propellant.

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<b><i>Purpose:</i></b> To evaluate the effect of pars plana vitrectomy (PPV) and internal limiting membrane (ILM) peeling for lamellar macular hole (LMH) with or without macular retinoschisis in highly myopic eyes. <b><i>Methods:</i></b> In this retrospective, consecutive case-control study, 21 highly myopic patients (22 eyes) with LMH were divided into two groups based on preoperative optical coherence tomography (OCT): the “flat group” had no macular retinoschisis (<i>n</i> = 10), and the “retinoschisis group” had macular retinoschisis (<i>n</i> = 12). The average follow-up time was 17.2 ± 12.6 months. Outcomes were based on 6-month postoperative best-corrected visual acuity (BCVA), integrity of the ellipsoid zone (EZ), external limiting membrane (ELM), and residual foveal thickness (RFT). <b><i>Results:</i></b> The appearance of the macula on OCT was normalized in 19 eyes (86.3%) at the final follow-up visit. Compared to the flat group, the retinoschisis group presented a significantly higher incidence of epiretinal membrane (<i>p</i> = 0.046) and lower refractive error (<i>p</i> = 0.033), shorter axial length (<i>p</i> = 0.0009), better integrity of ELM and EZ (<i>p</i> = 0.005 and <i>p</i> = 0.005, respectively), and better preoperative and postoperative BCVAs (<i>p</i> = 0.015). <b><i>Conclusions:</i></b> PPV is an effective method to achieve a high anatomical success, improve postoperative vision, and prevent foveal thinning in highly myopic eyes with LMH. In these eyes, the presence of retinoschisis strongly indicates the need for vitrectomy.

In order to quantitatively analyze the mesoscopic damage process of hydroxyl-terminated polybutadiene composite solid propellant under external load, periodic boundary conditions were applied to the representative volume element model based on sample composition and morphology, the mixed matrix containing aluminum powder was homogenized, and the hyperelastic matrix damage and bilinear/exponential particle–matrix interface cohesive model with initial damage were compiled through the secondary development of Abaqus. At the same time, a data interaction platform was constructed by means of Python and MATLAB, matrix and cohesion parameters were inverted according to the optimization algorithm and experimental data, and the whole process of propellant damage and fracture was simulated from the mesoscopic perspective. The results show that combining the adaptive particle swarm optimization algorithm and the Hooke–Jeeves algorithm can achieve the global optimal parameter inversion in 102 calculations, compared with the single local search algorithm, which can cut about 11% of the objective function values. Considering the matrix damage and the exponential cohesion model with initial damage, the optimal objective function value is 0.01635, which can more accurately simulate the propellant damage and fracture process compared with 0.02136 of a bilinear cohesion model.