This investigation is a part of the Thales project SaNdI. The goal of the SaNdI project is to provide a scheme for assessment of damages on composite sandwich structures in naval crafts, and also recommendations on actions after damage assessment. Impact damages may drastically reduce the strength of carbon fiber faced sandwich structures. In order to facilitate damage assessment it is important to be able to accurately predict the residual strength of a damaged carbon fiber sandwich structure. A plastic micro buckling approach is investigated in order to see whether it can be used to analytically predict the residual strength of carbon fiber sandwich structures. A parametric study on impact damage resistance and residual strength of sandwich panels with carbon fiber-vinylester faces and PVC foam core is conducted. Two sandwich configurations are studied. The first configuration consists of thin faces and an intermediate density core, representative of a panel from a superstructure. The second configuration consists of thick faces and a high density core, representative of a panel from a hull. Two different impactor geometries are used. One spherical impactor and one pyramid shaped impactor are used in a drop weight rig to inflict low velocity impact damage of different energy levels in the face of the sandwich. The damages achieved ranges from barely visible damages to penetration of one face. Residual strength is tested using in-plane compression of the sandwich plates either instrumented with strain gauges or monitored with Digital Speckle Photography (DSP).
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