Effect of Layer Material Properties on the Radial Stress at the Interface in Hybrid Tubes Made of Many Layers

Abstract

Composite cylinders possess characteristics not seen in other types of structures. First they are light weight as compared to metallic cylinders due to the light weight of composite materials. Secondly they do not have free edges (along the circumferential direction) which prevents delamination along free edges like that in composite plates or panels. Thirdly, they can be manufactured using automated fiber placement which provides good repeatability and high speed of production. Fourthly, they are corrosion resistant which makes them applicable for making pipes, or undersea transmission cables for electrical lines. Due to these characteristics, composite cylinders have found applications in pipes, and potentially as cross piece for landing gears for helicopters. Nonetheless, when subjected to bending loads, composite cylinders exhibit failure on the compression side. The failure is due to buckling of the material. The buckling seems to be caused first by delamination, which in turn depends on the radial stress at the interface between the layers. This paper examines cylinders made of two different isotropic layers. The effect of different elastic moduli and Poisson ratios on the development of the radial stresses throughout the thickness, particularly at the interface of the layers, is examined.