The Effect of Stacking Sequence and Coupling Mechanisms on Eigen-Nature of Composite Shafts

Composite materials have interesting properties such as high strength-to-weight ratio and relatively high damping characteristics compared to metals which make them very attractive for rotating systems. They also provide designers with the possibility of obtaining predetermined behaviors in terms of position of critical speed by changing the arrangement of the different composite layers orientation and number of plies. The composite rotating shafts used will be fabricated using hand layout technique by filament winding technique. Glass fiber (E-Glass) as reinforced with a matrix of polyester resin and hardener will be used to construct the composite layers needed. Five cases will be studied using composite shafts wounded by different layers of composite materials namely; different stacking sequence, fiber orientation angles, (L/D) ratio, boundary condition and finally various types of fiber volume fraction. In the theoretical part, the validity of the proposed theoretical model for evaluating the dynamic response of composite shafts will be examined utilizing the equivalent modulus beam theory (EMBT). In the experimental part, the frequency of composite shaft specimens will be measured by self-excitation and so critical speed of the rotating shaft will be determined by using the (TM1 MKII Whirling) machine apparatus. The numerical finite element technique is utilized to compute the eigen pairs of laminated composite shafts. A finite element model FEM has been developed to formulate the stiffness matrices using lamination theory. These matrices take into account the effects of axial, flexural and shear deformation on the eigen-nature of rotating composite shaft. Eigen natures of composite shafts were estimated through modal testing and are compared with (EMBT) results. The comparison between the numerical and experimental results proves that the suggested finite element models of the composite shaft provide an efficient accurate tool for the dynamic analysis of rotating composite shaft.