Composite materials are in use in the shipbuilding industry for a long period of time. Composites appear in vast number of fibre – matrix combinations and can be produced with several different production processes. Due to the specific nature of the composite material structure, the selection of the production process and the limitations in the quality control procedures, composite materials will always be subject to defects and imperfections which may, under certain circumstances, lead to the appearance and propagation of cracks. The size and the shape of the crack, the load type and the stress field in the material surrounding the crack will be crucial for crack growth and crack propagation. This paper reviews the composite material damage processes especially relevant for shipbuilding. The basic principles of composite material fracture mechanics are briefly explained, and finally, mechanisms responsible for the development of damage and fracture of composite materials are presented. This paper has emerged from the need to summarize information about composite material fracture and failure mechanisms and modes relevant for the shipbuilding industry.

No abstract

Sandwich structures are well-known and frequently used solutions in marine applications, especially when structural stiffness is required. An important part of the sandwich structure is the core, which usually carries shear loads. Therefore, choosing a reliable test method and knowing the exact shear properties of the particular core used in the structural design is beneficial for every engineer. Shear properties of the FlexyFoam M-55, a closed-cell, lightweight PVC foam with an apparent density of 60 kg/m3, have been investigated according to the ASTM C273 standard, using the tensile and compressive loading of metal supporting plates glued to the PVC foam sample. A digital image correlation (DIC) technique was used to monitor the crack propagation, and the appearance of secondary stresses at the foam-adhesive interface and strain field for the representative sample was presented. Displacement was measured using the testing machine sensors and compared to the measurements from the DIC technique. Specimen manufacturing details, surface preparation, and the gluing sequence were described, and measuring equipment and experiment settings were presented. Stress-strain curves have been presented and shear modulus and ultimate shear strength of the foam were compared for each test approach. The results were discussed and compared with the manufacturer’s data, as well as with foams of similar densities. The well-established approach in testing the core material was discussed, and recommendations were given to improve the testing procedure.

No abstract

No abstract