Stress Fields and Failure Mechanisms in Active Composite Structures

摘要

The design of an actuator system is driven by the ratio of output to input in terms of force and stroke for maximum structural efficiency. In order to avoid local failure and degradation due to fatigue it is necessary to consider the local stress conditions. The adaptive system is composed of the integrated actuator as well as the surrounding body system. Both together are exposed to the stresses and strains caused by the action of the actuator and the operational loads which act on the whole system at the same time, i.e. mechanical, thermal or moisture loads. The 2D stress models of today are not well suited for calculating the three-dimensional stress distributions within the deformed body system. Neither transverse stresses can be calculated nor the effect of changes in the layer stacking sequence to identify the optimal placement of active layers within the cross section. Hence a 3D solution that satisfies the conditions of the Theory of Elasticity is required. The strength behavior of the complex elastic system has to be accounted for in the design process. The 3D solutions correspond extremely well with test results.