A study of steady creep of layered metal-composite beams of laminated-fibrous structures with account of their weakened resistance to the transverse shift

Steady state creep of a hybrid metal-composite laminated bending beams of irregular patterns is considered. Beams consist of walls and load-bearing layers, attached at the top and bottom (shelves). The shelves are reinforced with fibers in the longitudinal direction, and the walls are reinforced either longitudinally or cross in the plane. Under the hypotheses of the Timoshenko theory the boundary value problem is formulated for the calculation of the considered beams, which allows taking into account the weakened resistance of the walls of the transverse shifts. The simple iteration method based on the idea of the secant modulus method is applied for linearization of the problem. The mechanical behavior of reinforced and unreinforced double seat beams and cantilevers in conditions of steady creep under the action of uniformly distributed transverse load is investigated. Cross sections of beams are I-shaped. It is shown that for homogeneous I-beams, the classical Bernoulli theory does not guarantee the calculated results in compliance within 20% accuracy, which is considered to be acceptable if the width of the shelf is comparable with the height of cross sections of beams. In the cases of metal-composite beams, the classical theory becomes generally unacceptable, because it lowers by several orders of magnitude the compliance of such structures in conditions of steady creep. It is demonstrated that the rate of shear strain, actively developing in their walls, must be considered. The consideration of these strain rates within the framework of the Timoshenko theory led to the discovery of new mechanisms of deformation of laminated beams which the classical theory does not find. It is shown that the change in mechanism of deformation can occur by increasing the density of reinforcement of shelves or walls.