Design and Evaluation of Three Methods for Testing Extension-Twist-Coupled Laminates

Abstract

Elastically tailored composite laminates are those laminates that have been designed with specifically tailored stiffness parameters. These parameters can be sized to give an out-of-plane response to in-plane loading, resulting in deformation modes not found in conventional homogeneous materials. Three different methods of testing extension-twist-coupled specimens are discussed. The benefits and limitations of each of the methods are highlighted. Quantitative results for each of the testing methods using a hygrothermally stable specimen are shown and compared to determine the applicability and suitability of each of the methods. A comparison of data with predictions from a shear deformation sublaminate plate theory and finite element method (FEM) is presented.

Extension-Twist Coupling Optimization in Composite Rotor Blades

“…The torsional stiffness of such laminates was determined in [41] based on geometrically nonlinear analysis. A number of test methods and apparatuses was developed in order to measure the twist angle under axial loading [27,32,33]. The first star cross-sections, obtained by joining several extensiontwist coupled laminated strips [21], as depicted in Figure 3…”