Composite Springs Made by 4D Printing

Abstract

4D printing is a manufacturing process which combines 3D printing with reconfiguration of the structure into a more complex shape. The normal 4D printing would involve the deposition of polymeric materials with special properties to make flat layers. These flat layers are then subjected to some activation mechanism such as heat, light, water absorption etc. The materials in the flat layers then react to the activation mechanism to change the shape of the structure. Most of the materials used in 4D printing have low mechanical properties. 4D printing of composites (4DPC) is similar to the 4D printing mentioned above, except that the materials are regular composite materials that have been used to make structures such as airframes. These materials are light, stiff and strong. Flat layers of the composite are laid using Automated Fiber Placement. The layers have different orientations to make unsymmetric laminates. Upon curing, the interaction of layers of different orientations will make the structure to be curved. This technique can be used to make structures of different curvatures, without the need to use complex molds (as such it can be termed as moldless composite manufacturing). This paper presents the mechanical behavior of composite springs that are made using 4D printing method.