Low-velocity impact of composite sandwich plate
Abstract
Much work has been done on impact resistance and impact tolerance of composite sandwich panel. However, there is no research predicts the impact force history of a composite sandwich plate and the corresponding stress distribution. Thus, the objectives of this research are to establish a model to analyze force response during the impact, application of a suitable failure criterion to explain the damage mechanism on the face sheets, and use the linear fracture mechanics to predict the propagation of delamination. Through the understanding of failure processing, a new type of core material and sandwich structure are designed to improve the damage resistance of core and face sheets. A finite element procedure was performed to predict the impact force history. Two types of impactor used on this study. For the spherical impactor, plate finite element is adopted. For cylindrical impactor, Plane strain finite element was employed. For plate finite element, a new model treated facing as two independent Mindlin plates, core material resisted transverse normal strain and transverse shear deformation, and Impactor was assumed as a rigid body. The impact force history is determined experimentally and compared with the predicted values for foam core and honeycomb core sandwich plate. Damage mechanisms are observed by X-ray radiograph and cross-sectional optic microscopic photographs. Maximum principle stress criterion is chosen to predict the onset of matrix cracking. Fracture mechanics combined with nodal release technique is used to predict the propagation of interface delamination. Design of new core construction and the introduction of film adhesive between the 0/90 interfaces are utilized to improve the damage inside the face laminate and core section. Basic material properties tests and impact tests are performed on both tradition and new core construction. A nonlinear materials behavior for film adhesive is employed to study the effect of this tough layer on outset loading of matrix cracking and growth of interface delamination.
Degree
Ph.D.
Advisors
Sun, Purdue University.
Subject Area
Aerospace materials
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