A STUDY OF IMPACT ON COMPOSITE LAMINATED SHELLS

Abstract

A comprehensive theoretical and experimental investigation is conducted to examine the characteristics of composite shells subjected to low velocity impact. An analytic impact force function is proposed for estimation of the contact force between a striker and a shell during impact. This is based on a spring-mass model and expressed in terms of the material properties and the mass of the striker and shell as well as the impact velocity. A set of solutions for prediction of the displacement, strain and stress responses of open composite laminated shells subjected to impact is presented. These solutions, based on a higher-order shear deformation theory (HSDT), are applicable to flat plates and open cylindrical and spherical shells impacted centrally by a solid striker. The proposed impact force function is incorporated into the solutions by using it to represent the dynamic load on the shell. From the solutions obtained, the effects of impact conditions (such as impact mass, contact stiffness and impact velocity), shell size and curvature on the contact force and deflection of the shell are examined. Also, transient stress distributions in a shell during impact are analyzed and the occurrence and locations of maximum stresses determined. Solutions for prediction of displacements, strains and stresses in closed cylindrical and ogival shells subjected to impact are also presented. These solutions facilitate study of the transient dynamic response of laminated composite cylindrical and ogival shells impacted at an arbitrary location by a solid striker. Central and non-central impact on a [08] glass/epoxy closed cylindrical shell is examined, as are the strain responses in an impacted [04] glass/epoxy ogival shell. These studies show that the occurrence and locations of maximum strain are governed by the history and location of the impact force. To complement the theoretical analyses, an impact test rig was designed and constructed to study the contact force and strain responses of laminated composite shells under impact. Impact tests were performed on cylindrical and ogival shell specimens. Experimental results show that the proposed theoretical analyses are applicable to the estimation of contact force and prediction of strains in impacted shells.