Investigation of the compression performance and failure mechanism of pseudo-ductile thin-ply hybrid composites

Glass/carbon hybrid specimens were designed and loaded in four point bending in order to generate stable compressive failure which allows for detailed microscopic study of the damage mechanisms. An optical measurement technique based on the displacements of five dots on the specimen edge was applied to monitor the strain of the carbon layer from the curvature of the sample. A loading frame suitable to be inserted into the vacuum chamber of a scanning electron microscope was developed. A previously tested specimen was deformed again in the loading frame and its polished edge surface was scanned while it was kept under significant deformation. This technique was successful in visualising the microscopic deformations and allowed for a deeper understanding of the damage mechanisms. Compressive fragmentation, sliding along the inclined fracture surfaces and local delaminations around the crack tips were confirmed by micrographs. An explanatory schematic was generated, highlighting the microscopic displacements of a fragment upon further loading.