Numerical analysis of dynamic strength of composite cylindrical shells under multiple-pulse exposures

The target of this research is studying the fiberglass cylindrical shellswith exposed ends resulted from the cross-winding of tapes made of an unidirectional composite material. The aim of the study was to develop a numerical technique to model a progressive fracture of laminated composite cylindrical shells under multiple-pulse loading with an internal pressure of a various intensity. Kinematic model of deforming the laminate package is based on the applied geometrically nonlinear theory of shells. The formulation of geometric dependencies is based on the relations of the simplest quadratic variant of the nonlinear elasticity theory. The physical relations of the elementary layer are formulated based on the generalized Hooke's law for the orthotropic material based on the hypotheses of the applied shells theory. The process of a progressive shell failure is described within the degradation model of stiffness characteristics in elementary layers of a multilayer package which is based on Hoffman's criteria for composite materials and on the criterion of maximum stresses for the fibers. The process of damage accumulation in the shell material due to a multiple application of impulse load is takeninto account by means of the computational scheme in which the calculation of the current stress strain state is carried out with stiffness characteristics obtained in the model of their degradation under previous loading. Energetically consistent system of motion equations of the applied shell theory is deduced from the stationarity condition related to the functional of the shell total energy. A numerical method for solving the formulated initial-boundary value problem is based on an explicit variational difference scheme. The accuracy of the considered techniqueis proved by comparing the obtained results with the known experimental data. The results of how the number of loadings affects the value of marginal circumferential deformationsare presented. It is established that the level of maximalring deformations is approximately ten times less than their limit values compared to a single loading.