Reconsidering Laminate Nonsymmetry

What is it about?

Composite materials are often constructed through the stacking of prepreg layers. The fibre direction of each layer may be oriented at different angles throughout the laminate to change the laminates elastic properties. When specifying a stacking-sequence it is generally considered best practice to ensure that the laminate is symmetric about the midplane, however, this requirement reduces design freedom significantly. One primary reason for the reluctant to use non-symmetric laminates is the potential for warpage during cure. In this paper, we revisit this symmetric-only design rule and demonstrate that laminate non-symmetry offers a vastly increased design space for modest increases in residual strains. Following this observation, we recommend that laminate non-symmetry should be considered using a response-based metric, in effect classifying it as another source of manufacturing defect.

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