Families of Hygrothermally Stable Asymmetric Laminated Composites

Abstract

Necessary and sufficient material-independent conditions are derived for hygrothermal stability of a laminated composite plate with plies made of the same specially orthotropic material based on classical lamination theory. The minimum number of plies required to obtain an asymmetric hygrothermally stable stacking sequence is proven to be five, and families of stable laminates are identified for six, seven, and eight plies. A sensitivity analysis demonstrates the robustness of hygrothermally stable solutions to small errors in ply orientation. A finite element analysis of geometric and ply orientation imperfections was performed to verify the robustness of the classical lamination theory results. Hygrothermally stable asymmetric laminate specimens were fabricated to confirm the analytical predictions.

General Theory of Coupled Thermally Stable Anisotropic Laminates

“…In a sense, uncoupling corresponds to annihilate their anisotropic part or, which is the same, to impose that they are isotropic. An accessory result is that, being null the isotropic part of V, it is V xx (θ) = −V yy (θ) ∀θ, a result already given in [2] but only for the case θ = 0.…”

“…Winckler, in his PhD thesis and in some related papers, [19], [20], has been, perhaps, the first to propose some sufficient rules for the design of warp-free coupled laminates. Chen has then given some other sufficient rules on the subject, [1], as well as Cross et al, [2], in a paper presenting some families of warp-free laminates, work extended in a subsequent paper by Haynes and Armanios, [4]. In these last two papers, the authors also look for stacking sequences optimizing the thermal warping.…”

Optimization of Hybrid Laminates with Extension-Shear Coupling

“…Now, the extension-shearcoupled effect of laminates is analyzed under the ply angle existing deviation, which is based on the Monte Carlo composite laminates robustness analysis method. Assume that the paving angle of the k-ply for the hybrid A F B 0 D S laminates with immunity to HTSD is θ k ± Δθ k , in which θ k is the theoretical paving angle of the k-ply and Δθ k is the angle deviation and with the value of Δθ k = 2° [17]. Figure 6 shows the error distribution of the extensionshear-coupled effect for the 16-ply laminates and the 17-ply laminates in Table 2 under 10,000 random samples.…”

Extension-Twist coupled laminates for aero-elastic compliant blade design

“…This hygro-thermally curvature-stable or warp-free laminate sub-class also facilitates the design of aero-elastic compliant rotor blades with extension-twisting coupling; this time by employing extensiontwisting coupling rather than extension-shearing coupling at the laminate level. The discovery of this particular class of coupled laminate has had a strong influence on the subsequent studies in the literature, including: maximizing the extension-twisting coupling response 8,9 and/or; integrating additional forms of mechanical coupling response, e.g. bending-twisting coupling 10 .…”