Design rules for composite sandwich wakeboards

Wakeboarding is a water sport born in the mid 1980s that derives from surfing and water skiing. The objective of this work is to understand the failure mechanism and evaluate the maximum hydroelastic loads during the slamming phenomena of the board used in this sport, in order to provide reliable design rules to follow during the design process. Wakeboards are usually built as a composite sandwich structure, with plastic foam core and CFRP (carbon fibre reinforced plastics) or GFRP (glass fibre reinforced plastics) faces. Several specimens were extracted from a real board and tested in three point bending to investigate the major failure mechanisms. These data are later used in a parametric full-scale SPH numerical model investigation of the water-entry event. The numerical results show that, due to the fluid–structure interaction, there is a maximum deformation that the board cannot overreach even for very high impact energies. This limits the maximum impact stresses reached during the water entry of wakeboards. From these numerical results, mathematical relations between design variables are drawn by using analytical formulas based on classical sandwich theory. As result of this research, practical guidelines (formulas, tables and graphs) on the effects of total mass, initial impact velocity, board curvature and core and face strength and thickness are outlined to give reliable design rules.