Composites for commercial ships

Licentiate thesis, 2015

Composite materials have been used in marine applications for more than 50 years, and benefits such as low weight, low maintenance requirements and freedom of design are well known. A wider use of composites in larger, commercial vessels has been limited by initial costs and fire regulations, but both of these obstacles are diminishing. Increasing fuel costs and emission requirements have heightened the value of lightweight structures. Moreover, the introduction of SOLAS Regulation 17 has also provided the possibility of building ships from materials other than steel and aluminium. Composite designs must be as cost-efficient as possible in order to compete with traditional steel or aluminium designs, and this effort requires a thorough, balanced and open-minded design process. Stretching the existing concepts or spending time and money on optimizing isolated systems or details is often not the most beneficial approach from an overall perspective. To efficiently produce many rapid design iterations, knowledge of the basic design process is required as well as more detailed knowledge of the relationships among structural designs, materials and systems. The work presented in this monograph provides ship structure designers and decision-makers an understanding of what the design process practically means in terms of actual calculations, numbers and results. This goal is accomplished by stepping through the process, beginning with simple panel-scantlings and global strength calculations, introducing additional requirements, and finally, examining the case of a superstructure to which the previous findings are applied. Comparisons between structures and materials are performed to obtain actual figures for cost and weight relations. Because composite designs are characterized by a higher initial cost but lower operational costs, a life-cycle cost analysis is necessary. This analysis can be used to compare different concepts and to also assess the competitiveness of a composite design at an early stage in order to identify projects in which composites have the highest potential to succeed. For this purpose, a simplified fuel-cost calculation can also be useful.