Comparative Stress-Strain Analysis of Bidirectional Braided Hydraulic Hose Approximated by Unidirectional Laminate Theory

Thick wire reinforced braided hydraulic hose is modeled as an equivalent thin-shell laminate consisting of alternate unidirectional sublayers. Stacking sequence and helical orientation of the sublayers are described both by a symmetric and an overlapping laminate. A knock-down factor, wire misalignment, is also applied to each model. Gough-Tangorra micromechanics is used in conjunction with a linear finite element code to solve for stress-strain behavior of the symmetric laminate throughout the hydraulic pressure range from an unloaded state to minimum burst conditions. Classical laminate theory is developed and applied to the overlapping model since the finite element code is not directly applicable.

Both models exhibit satisfactory agreement with experimental data and output from a set of theoretical nonlinear equations. In addition, computed hose axial stiffnesses agree with those measured from static dead-weight loaded hose sections. Calculated wire tension distribution between layers follow all trends exhibited by the predictive equations. At elevated pressures near hose instability, (rapid length increase at constant pressure) wire tensions are found to be considerably less than the minimum wire breakage tension.