OPTIMAL 3D IMPACTORS PENETRATING INTO LAYERED TARGETS

Optimization of 3D sharp high speed impactors with given form of a lon gitudinal contour, length, and volume, penetrating into layered ductil e targets, both for conical and thin non-conical strikers using approx imate models is studied. It is found that the impactor with the minimu m drag moving in a homogenous target with a constant velocity penetrat es to the maximal depth into a semi-infinite target and has the minima l ballistic limit when it penetrates into a finite thickness target, r egardless of the distribution of the material properties of the target along its depth, the number of the layers, etc. Using the analogy wit h the hypersonic flow over the flying projectiles it is predicted that the optimal impactor should have a star-shaped form of the cross sect ion. If an impactor has a polygonal cross sections allowing the inscri bed circles, the ballistic limit and maximum depth of penetration are independent not only of the properties of the target but also of the f orm of the polygon in the cross section and equal to the corresponding values for the inscribed body of revolution. (C) 1997 Elsevier Scienc e B.V.