Finite element analysis of functionally hybridized carbon/glass composite shafts

Abstract

External torque on circular composite shafts produces linearly decreasing shear stresses along radial direction. The inner layers never stressed as much as outmost layer. Accommodating fiber stiffness of each layer based on these linearly decreasing stresses may be advantageous. To reduce the cost of carbon fiber-reinforced composite drive shaft, inner layers of shaft can be reinforced by hybrid fiber systems with less stiffness. To achieve that, while the top layer is still reinforced with carbon fiber, inner layers can be reinforced with the mixture of glass and carbon fiber. Without changing the fiber volume fractions, replacement of some carbon fiber with glass fiber will reduce the overall stiffness of fiber system. Mixture ratio or hybrid ratio can be calculated using linearly decreasing stress levels and the rule of mixture. These hybrid composite shafts can be manufactured by filament winding technique. During filament winding, composite shafts are wound layer by layer and filament type can be changed between the layers. The proper mixing ratio can be achieved by arranging the fiber count in each filament bundle. The relation between geometrical parameters and hybrid fiber volume fractions of composite shaft was derived. Finite element analysis on carbon fiber and functionally hybridized glass/carbon fiber shafts with same geometry was conducted. Stress, strain, and moment behavior of both shafts were compared. The possible advantages and disadvantages of hybridization were discussed.