An experimental study of the insert joint strength of composite sandwich structures

This paper addresses an experimental study of the pull-out and shear failure loads of composite sandwich insert joints. For specimen fabrication, a Nomex honeycomb core and a carbon–epoxy composite were used. The film-type adhesive FM73 was used for core and face co-cured bonding. Specimen sizes are 120 × 120 mm2 for the pull-out test and 60 × 120 mm2 for the shear loading test. About 80 specimens of 16 different types depending on the core height and density, face thickness, insert clearance, and loading direction were tested. The results show that while the insert joint failure loads for pull-out loading are affected by the core height and density, they are also greatly influenced by the face thickness. The joints with 0.11 mm clearance between the insert flange and the composite face, which is filled with potting material, showed larger failure loads compared to tightly fitted insert joints. In the shear loading, the failure loads of joints were dominated by the face thickness, while core properties such as the core height and direction had little effect on the failure load.