An Experimental Investigation of Combined Symmetric-Asymmetric Composite Laminates

Guy Kemmann,Oliver Myers

doi:10.3390/jcs3030071

Abstract

It has been found that certain asymmetric composite laminates exhibit bistability, where the composite laminate exhibits multiple stable static equilibrium states. If the bistable composite is actuated, it will snap to its secondary equilibrium state and then remain there without further actuation. This study investigates how the amount of symmetry in a combined symmetric asymmetric rectangular laminate under an imposed clamped edge boundary condition affects the bistability and the curvature of the laminate. Laminates with varying amounts of asymmetry were fabricated and then measured using a profilometer to capture the curvatures of the equilibrium shapes. The results showed that up to 20% symmetry can be introduced in the laminate without a substantial loss in snap through curvature, and that up to 83% symmetry can be introduced in the laminate before bistability is lost. Finite element simulations were conducted in Abaqus and showed good correlation with the experimental results.

Highlights

The first major research into the behavior of bistable composites was done in 1981 by Michael W
Hyer experimentally investigated the phenomenon of asymmetric composite laminates and how their cured shapes diverged from the predictions of classical lamination theory
The representative snap through curvatures of the laminates were of primary interest, as their presence denotes the existence of bistability

Summary

Introduction

The first major research into the behavior of bistable composites was done in 1981 by Michael W. Hyer experimentally investigated the phenomenon of asymmetric composite laminates and how their cured shapes diverged from the predictions of classical lamination theory. The principal phenomena behind the bistability lies in the thermal expansion coefficients of the fibers. The thermal expansion coefficient in the fiber direction is less than the thermal expansion coefficient perpendicular to the fibers. When an asymmetric laminate is made, there exists a mis-match in the thermal expansion coefficients about the mid plane of the laminate. An asymmetric laminate will exhibit different types of curvature post cure due to residual stresses induced by dissimilar thermal expansion coefficients

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