Composite laminates constructed in an asymmetric layup orientation of \[0~i~,90~i~\]\[CMN1\] , i>0, exhibit two stable equilibrium positions and may be actuated to snap from a primary cure shape to an inversely related secondary stable shape. This study aims to develop a comprehensive functional description of thick bistable laminates, whose increased thickness risk the loss of bistability, through previously established analytical approaches and verification via experimentation. The principle of minimum potential energy is applied to two materials and analyzed using the Rayleigh-Ritz minimization technique to determine the cure shapes of carbon fiber reinforced polymer laminates composed of T300/914 and AS4-8552. These materials were modeled to act as square thick bistable laminated composites with sidelengths up to 36 inches. Visualizations of the out-of-plane displacements are shown with a description of the Rayleigh-Ritz analysis. Additionally, a finite element model (FEM) created in Abaqus 6.14 CAE and experiments using TR50S-12K/Newport 301 prepreg are used to further describe and develop the fundamental description for thick bistable laminates in terms of loss of bistability, actuation energy, and shape.

 

The analytical model is an extension of Hyer’s (1981) and Mattioni’s (2009) work applied to thick bistable laminates where the primary assumption was the x-axis curvature equaled the negative y-axis curvature for the primary and secondary stable positions, respectively. This assumption leads to the already cemented conclusion that bistable laminates, once cured, take on one of two inversely related paraboloid shapes. \[CMN2\] FEM simulations contradicted this by showing an averaged 11% difference in magnitude between the two aforementioned curvatures. Furthermore, fourth \[CMN3\] order polynomials were used to describe the curvature along the axes differing from the previously used Menger curvatures, a three-point curvature approximation. Bifurcation plots generated from FEM simulations clearly showed bistability existed to approximately 80 plies; however, the energy landscape plots indicated loss of bistability at 32-36 plies

 

Experimentation was performed on a test stand mimicking the same boundary conditions used in FEM while applying a centroidal load. Experimental observations showed decreased peak displacements of stable cure shapes. Experimental observations also indicated that the x-axis curvature had a significant difference in magnitude compared to the negative y-axis curvature. However, the existence of bistability agreed with FEM energy landscape plots, with clear “snaps” ending at thicknesses of 32-36 plies. \[CMN4\] Moreover, actuation energy and actuation force were also found to be significantly less in magnitude during experiments than compared to FEM simulations which can be attributed to the combination of material property differences between AS4-8552 and TR50S-12K, limitations of the experimental setup, and hand layup fabrication errors. Lastly, this paper shows that there is viability of thicker bistable laminates to be used in macroscale applications where shape morphing or shape-retention attributes are a necessary constraint.


Functional Description for Thick Bistable Carbon Fiber Laminates With Rayleigh-Ritz, Abaqus, and Experiments

Division / Sponsors: 
Aerospace Division

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2020/volume/84027

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