Development of omega stiffeners using 4D printing of composites

4D Printing of Composites (abbreviated as 4DPC) is a manufacturing technique where a composite structure of complex geometry can be made without the need to use a complex mold. Only a flat mold is used. As such there are significant savings in time and money. The technique can also be used to make structures that conventional manufacturing technique cannot. The technique relies on the anisotropic nature of unsymmetric laminates. In this paper, this technique is used to develop omega shape (omega) aircraft wing stiffeners. The lay up sequence allows a flat stack of prepregs to transform into the shape of the omega upon curing and cooling to room temperature. Foam is poured into the cavity of the structure to provide core sandwich support. The stiffener is tested under three-point bending. The flexural stiffness of the stiffener is determined using a model and laminate theory. The calculated stiffness is compared with experimental results. Good agreement is obtained.