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.
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.
With the aim of improving the environmental sustainability in the field of maritime transport and with special reference to multimodality and 'green' solutions for coastal transport, within the METRO project (Maritime Environment-friendly TRanspOrt systems), funded under the Interreg VA CBC Programme Italy-Croatia, a project of a hybrid Ro-Pax medium range ferry for coastal navigation in the Adriatic area is developed. The paper presents a part of the conceptual design for the assessment of the global hull structure strength, which is not common for this phase of the project, and that is the structural analysis of the complete ship. For this purpose, a detailed computer model of the geometry of the whole ship was made, which includes all primary and basic secondary structural elements, with the aim that such a model can serve later as a good basis for classification and workshop documentation production during contract phase. Additionally, a preliminary calculation of the scantlings of the complete ship was performed according to BV rules and regulations using the MARS2000 software package, with regard to bending and buckling. Loads were modeled according to real conditions for two unfavorable loading conditions, and static linear analysis was performed using the LS-DYNA software package. The global analysis of bending strength in still water could reveal problematic areas in the structure.
A competitive advantage over other shipyards is extremely important in the high-stake shipbuilding industry. Typically, a competitiveness analysis of a shipyard measures productivity based on specific parameters, such as tonnes or compensated gross tons produced per consumed working hour. The authors of this paper consider identifying the technological level required to achieve this productivity as essential, including other information relevant for the shipbuilding process. Therefore, a methodology for determining the technological level of shipyards is proposed based on defined criteria and a structured evaluation. The criteria were devised and structured hierarchically. The methodology also offers company management a solution for continuous monitoring for improving shipyard design and production processes.
Deformations of steel material in shipbuilding and marine technology applications as a result of mechanical or temperature influences are a well-known problem. However, in the modern shipbuilding industry, the application of alternative materials, especially composite materials, in the structure and for the equipment of the ship is increasingly represented. Consequently, there is a need to determine the deformation and change of characteristics of such composite materials as a result of various mechanical, and especially temperature influences that cause the so-called shrinkage. The basic composite production process involves connecting the matrix with a catalyst and accelerators that create temperature, then the material shrinks by cooling when it can change its dimensions and characteristics. Also, in order to achieve the best possible mechanical properties, composite materials are specially heated and then cooled according to strictly defined processes and curves. The ability to predict the characteristics and parameters of such deformations is important in the context of the application of composite materials. To define such deformations, different methods are used within individual numerical solvers, whose results can differ significantly from each other. Therefore, the authors in this paper present an established methodology for predicting mechanical and temperature deformations, and modelling of composite materials, based on the analysis of analytical methods and numerical solvers with the aim of defining the most accurate numerical solver. By applying the presented methodology, it is expected to raise the level of accuracy and quality of composite materials production as well as to raise the quality of design solutions and efficiency of production procedures during shipbuilding in particular, but also within different marine technology applications and during the product’s life cycle.
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