Abstract: A mandrel around which fiber-reinforced resin is wound, the mandrel including a cylinder portion having a plurality of first flat surface portions, and a pair of dome portions that are formed at respective ends of the cylinder portion and each include a plurality of second flat surface portions.

Abstract: A mandrel around which fiber-reinforced resin is wound, the mandrel including a cylinder portion having a plurality of first flat surface portions, and a pair of dome portions that are formed at respective ends of the cylinder portion and each include a plurality of second flat surface portions.

Abstract: The durability performance of a structure is virtually predicted, enabling the optimization of the durability performance. In a first act, the structure is modeled by a series of calculation points. Then, for each point, the stresses and strains brought by load cycles and defining hysteresis branches are determined. Then, an accumulated damage due to the load cycles is predicted and stored. For the prediction, first, using a hysteresis operator, a change in the stress along a portion of a hysteresis branch is calculated as a function of a change in the load in time, and, second, using the change in the stress and the stored accumulated damage, a change in the damage is calculated. Hence, also a change in the properties, including the stiffness, of the structure is calculated. Then, a further change in the stresses and strains is calculated on the basis of the change in these properties to determine a new adapted hysteresis branch.