Introduction to Composites

Anisoprint technology is intended to produce lightweight, stiff and strong composite parts. Understanding composites is crucially important to extract maximal profit from the technology. Therefore, we wrote this guide to share our vision of composites and to assist you in understanding of these awesome materials.

Structural materials provide sufficient stiffness and strength. These characteristics allow a structure to maintain its shape and dimensions under loading or any other external action.

Typical structural materials are steel, aluminum, titanium alloys, concrete and some other. In addition, some composites are also structural materials.

Composite materials (composites) consist of several components with different properties and distinct boundaries between the components. The composites can be “filled” with some particles or short/chopped fibers or “reinforced” with long (endless or continuous) fibers. A matrix is a material that bonds the fibers together or is filled with short fibers. Typically, the matrix has much lower mechanical properties than the fibers.

So, further we will talk mainly about continuous fiber composites.

Reinforced composites have high stiffness and strength in the fiber direction and they are also lightweight. Therefore, there is a growing interest in such structural materials in aerospace, automotive, shipbuilding industries where weight plays a paramount role.

At the same time, reinforced composites have rather low properties in transverse direction.

Laminates with different stacking of composite layers are commonly used to counter this weakness. In such structures, layers with different orientations are designed to carry various acting loads.

This is the most popular, but not really good way to produce composite structures. Effective properties of the laminated composite are much less than the properties of the unidirectional composite in fiber direction.

If you need to joint composites or make some kind of hatch in a composite structural element, you will encounter the fact that you need to drill, mill or cut the composite material. Drilling, milling and cutting significantly reduce strength of reinforced composite in vicinity of the machined edge. The strength can drop down several times! So, the machining is actually killing the idea of reinforced composites application.

The most effective way to utilize potential of fiber reinforcement is lattice anisogrid structures. The peculiarity of the structures provides an effective distribution of loads along the fibers because the major acting loads run along the grid ribs i.e. in fiber direction. Thus, lattice anisogrid structures possess high weight efficiency in contrast to laminates.

The lattice structures are not afraid of cutouts and do not need drilling and milling. For these structures you can use special inserts.

Conventional composite technologies (winding, fiber placement) can produce parts only with geodesic and quasi-geodesic reinforcement paths, and regular grids. Structures with irregular grid density and non-geodesic reinforcement could provide more efficient distribution of acting loads and, as a result, weight reduction. However, such structures cannot be obtained by the conventional technologies.

Currently, only 3D printing allows to obtain composite parts with complex shape and high flexible fiber reinforcing paths. With 3D printing you can control anisotropy and utilize potential of fiber reinforcement with maximum efficiency. By the way, that’s why we are called Anisoprint (anisotropic printing or printing with control of anisotropy). You do not need to cut fibers. You can manufacture any hole in composite part without drilling and with reinforcement. Moreover, Anisoprint technology (Composite Fiber Coextrusion) uses thermoplastic matrix that increases impact resistance of a part in contrast to conventional thermosetting composites.

In conclusion of this guide, we would like to make a very important point. Composites are completely different from conventional materials (metals, plastics etc.). They are significantly anisotropic and inhomogeneous. This means that a metal (plastic) part and a composite part having the same purpose have to possess completely different designs! If you want to substitute a metal part with a composite part you should redesign one.