Design and evaluation of test apparatuses and methods for extension-twist coupled laminates.

摘要

Elastic tailoring of laminated composite materials is an enabling technology that has potential for significant weight and cost savings and reduced mechanical complexity with added design flexibility. The ability is available for engineers to prescribe complex deformation modes through material selection, stacking sequence, and component geometry. One such deformation mode is extension-twist coupling. As an axial load is applied, the component extends and twists. Verification of this behavior is needed to validate analytical tools, yet testing devices must not influence the behavior.;Three testing apparatuses have been developed and evaluated for testing extension-twist coupled laminated strips: a thrust bearing based apparatus, a free rotating frame apparatus, and an air bearing apparatus have been developed. An evaluation and comparison of the methods have shown that the air bearing apparatus best meets the demands for the accuracy, precision, and reliability needed of a testing method.;Furthermore, the accuracy of the air bearing apparatus has highlighted a geometrically nonlinear behavior of extension-twist coupled laminates that has been investigated and quantified.