3D tomographic characterization of sandwich structures

• Integrally manufactured GFRP sandwich composites from fiber spraying were examined.
• Image analysis procedures for micro-CT characterization tasks were developed.
• Manufacturing deviations of honeycomb cores were evaluated and extracted.
• Fiber orientation through core impression was measured in 3D from CT scans.
• Impact damage was non-destructively quantified for the face sheet and the core.

Computed micro-tomography (μ-CT) is widely used in non-destructive testing (NDT) of components and material characterization on the micro-scale. The investigation of industrial components is mainly concerned with the geometric characteristics and contour accuracy while in material science the focus is on the micro- and meso-structure of the applied materials or damage characteristics. The production of integrally formed sandwich materials poses a fundamental challenge for a separation of the scales and the successful measurement of characteristic features using μ-CT. In this work we present several μ-CT analysis techniques for a quantitative description of the processing parameters, the apparent micro- and meso-structure and impact deformation in sandwich structures. Therein the variations in honeycomb cell geometry and face-sheet fiber orientation are characterized using distribution functions extracted with 3D image analysis techniques. The knowledge of cell geometry thereupon allows the characterization of cell deformation due to varying impact loads. The detection of characteristic properties for an optimization of the process and a realistic localization of morphological weak spots and damage zones are demonstrated. Finally the restrictions of the methods are outlined and discussed with respect to the application range and application possibilities.