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The impact response of an ultrahigh molecular weight polyethylene (UHMWPE) fiber reinforced polymer matrix composite laminate has been investigated. The laminate encapsulated an aluminum alloy sandwich panel whose corrugated core was filled with prismatic alumina inserts. The laminate encased hybrid core target could sustain ceramic prism base impacts by a spherical, 12.7 mm diameter steel projectile with velocities in excess of 2.7 km s-1. This was 150% higher than the ballistic limit of an equal areal density, similarly encapsulated aluminum plate target. By contrast, when the projectile impacted a hybrid core target at the apex of a ceramic prism insert, failure of the UHMWPE laminate on the rear face occurred at a lower impact velocity. High-speed imaging, three-dimensional digital image correlation and x-ray tomography measurements are used to show that upon impact the projectile and the ceramic insert fragment. These fragments then load the UHMWPE laminate on the rear face with a significantly reduced pressure compared to the impact pressure of the projectile on the front surface of the target. The loading area on the inner surface of the rear laminate was highest for a prism base impact and lowest for a prism apex impact. The inability to penetrate the rear laminate of the base impacted samples is consistent with the recent identification of an impact pressure controlled mechanism of progressive penetration in this class of laminate.

An acceleration model and a jerk model are proposed in this paper for kinematic state estimation of re-entry ballistic targets. The models proposed here use fully coupled equations of the target kinematics, without assuming any model structure for variations of ballistic coefficient and air density as found in the literature. The novelty of the algorithms lies in the bootstrapped computation of the model parameter γ, which is the ratio of air density and ballistic coefficient, at every time step, utilizing the estimated velocity and acceleration. γ and its time derivatives, thus computed, are used for parameterization of DA and DJ models for estimating position, velocity and acceleration. This makes the algorithms inherently adaptive to the variations of the ballistic coefficient and the air density during the re-entry trajectory. It is demonstrated that the proposed models produce unbiased estimates of target acceleration as opposed to biased estimates from the existing models. [ABSTRACT FROM AUTHOR]

A ballistic impact test program was conducted to provide validation data for the development of numerical models of blade out events in fabric containment systems. The impact response of two different fiber materials—Kevlar 49 (E.I. DuPont Nemours and Company) and Zylon AS (Toyobo Co., Ltd.) was studied by firing metal projectiles into dry woven fabric specimens using a gas gun. The shape, mass, orientation, and velocity of the projectile were varied and recorded. In most cases the tests were designed such that the projectile would perforate the specimen, allowing measurement of the energy absorbed by the fabric. The results for both Zylon and Kevlar presented here represent a useful set of data for the purposes of establishing and validating numerical models for predicting the response of fabrics under conditions simulating those of a jet engine blade release situation. In addition some useful empirical observations were made regarding the effects of projectile orientation and the relative performance of the different materials. [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]