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In this paper, a modified laminated finite-element model based on subcell of unit cell and CDM material model was developed in nonlinear explicit finite-element code to investigate the dynamic response of 2D triaxial braided composite under ballistic impact of projectile. Six subcells, which were considered as laminate with different stacking sequences using solid elements, were employed to represent one unit cell of triaxial braided composites, therefore, the fiber-laying direction of braiding architecture is reproduced. In the prediction of the subcell model, an approximate round conical deformation area forms in the target and the failure modes are mainly longitudinal and transverse cracking due to tension. Compared with the continuum model, the subcell model is capable of analyzing the energy absorption of fiber in each direction. Although the failure modes are similar for both methods, the subcell model is more effective in prediction of impact wave propagation than the continuum model because it describes the fiber arrangement of triaxial braided composites. The developed subcell model will be an effective tool for the design process of carbon/epoxy composite fan casings. [ABSTRACT FROM AUTHOR]

Coning motion has been detected in flight experiments of many spinning projectiles for decades and the stability analysis of this motion has been extensively studied recently. In this paper, a novel optimal control algorithm based on stability analyses is developed to suppress the coning motion. A Lagrangian functional is built to compute the optimal control that minimizes the coning motion for a given control cost. Then a linearized approach, which produces accurate enough control within the range of parameters considered, is proposed to reduce the computational cost. It is analytically presented that the optimal solution of this linearized optimization is unique at any given values of control cost. The analytical analysis also indicates that there exists a direct solution of the control that approaches the linearized optimal control when the control cost is small enough and that this direct solution can be obtained much more efficiently than the linearized optimal control. The controllability problem associated with this optimal control algorithm is also discussed and the results shed lights on the choice of numerical parameters in the optimization. These optimal control algorithms are implemented to calculate the optimal control that minimizes the coning motion induced by initial disturbances to a wrap-around-fin missile. [ABSTRACT FROM AUTHOR]

Due to the importance of the ballistic trajectory computation including the estimation of launch point and impact point problems, a fast and accurate model is needed to increase the weapon precession. A discrete time transfer matrix method is developed and presented in this paper to compute the trajectory for both fin- and spin-stabilized artillery projectiles. This method is based on discretizing the projectile continuous nonlinear system into a set of linear equations using a second-order Taylor series. These equations are collected into one transfer matrix which can be used in trajectory prediction with high computation speed by evaluating a set of algebraic equations instead of integrating differential equations. Results demonstrate that the presented formulation agrees very well with those obtained numerically using the well-known nonlinear 6-degree-of-freedom model. [ABSTRACT FROM AUTHOR]

A numerical study is carried out to investigate a 7.62-mm bullet turning at the trajectory apex, particularly when fired vertically. The bullet model includes an aerodynamic model, which basically covers angles of attack up to 180°. Computational fluid dynamics are used to estimate the aerodynamic properties at the high angles of attack. The role of aerodynamic moment, and particularly Magnus phenomena, in turning at the apex is studied. A positive Magnus moment tilts the total aerodynamic moment vector clockwise and generally drives the bullet turning nose down. The bullet turning was detected through a flat spin-type maneuver. The Magnus-moment oscillatory behavior and/or the Magnus-moment-caused bullet instability may occur during the turning at the trajectory apex. These were found to have a negligible effect on the bullet-turning launch angle, but they may contribute considerably to the bullet falling-phase behavior. Possibilities to affect the bullet descending part of the flight are also shortly considered. [ABSTRACT FROM AUTHOR]