Stiffness analysis of filament wound composites considering filament crossover and undulation

Aimed at the meso-structure of crossover and undulation region in filament wound composites, a meso-scale analytical model is proposed. First, the crossover and undulation region are classified to two types, i.e. the circumferential crossover and undulation region, and the helical crossover and undulation region. Next, based on the filament wound surface, parallel cross-section was used to discrete spatial structure model of undulation region, which will be discretized to numbers of sub-models to describe the meso-structure of crossover and undulation region of filament wound composites by using meso-parameters such as fiber bundle inclination angle, size of resin rich area, volume fraction, cross-section shape and size of fiber bundle. With this meso-scale model and the laminate theory, a method for calculating the equivalent stiffness of crossover and undulation region of filament wound composites is eventually established. The effects of cross-section, inclination angle of fiber bundle and the volume fraction of resin rich area on local area equivalent stiffness were studied. The results show that the elastic modulus for circumferential crossover and undulation region decreases to greater extent as compared that of the helical crossover and undulation region. Significant decrease in elastic modulus and shear modulus and increase in Poisson's ratio are found for resin rich area. Thickness increase and cross-section change of fiber bundle have evident effects on the equivalent stiffness of crossover and undulation region.