Hybrid composite rods subjected to excessive bending loads

Glass fiber/carbon fiber/epoxy hybrid composite rods were investigated in this research for their resistance to excessive bending. The rods are presently being used as the load bearing component of the Aluminum Conductor Composite Core/Trapezoidal Wire (ACCC/TW™) design. The ACCC/TW™ design is one of the most serious candidates to replace the existing conductor designs based on steel and aluminum wires. The effects of mandrel size and thickness of the insulating glass fiber composite sheath on the axial compressive stress state during bending of the ACCC rod were numerically investigated by performing non-linear finite element analyses of the conductor wrapping process. In addition, two sets of compression experiments were performed on composite specimens in order to determine the ultimate compressive strength of the ACCC rod and of the carbon fiber composite alone. During the compression tests, acoustic emissions were monitored from the specimens to determine if a different failure process exists for the hybrid composite as opposed to a traditional uni-directional long fiber composite. Proof tests, and subsequent Scanning Electron Microscope (SEM) work of each type of composite were also performed to better understand the failure process. It was clearly demonstrated in this research that ACCC rods will be mechanically damaged by excessive bending over small diameter mandrels used for transportation and installation purposes. This work should be of great help to the manufacturers and potential users of the ACCC conductors around the world.