Anisotropic Material Behavior of 3D Printed Fiber Composites

Literature has shown that 3D printed composites may have highly anisotropic mechanical properties due to variation in microstructure as a result of filament deposition process. Laminate composite theory, which is already used for composite products, has been proposed as an effective method for quantifying these mechanical characteristics. Continuous fiber composites traditionally have the best mechanical properties but can difficult or costly to manufacture, especially when attempting to use additive manufacturing methods. Traditionally, continuous fiber composites used specialized equipment such as vacuum enclaves or labor heavy hand layering techniques. An attractive alternative to these costly techniques is modifying discontinuous fiber additive manufacturing methods into utilizing continuous fibers. Currently there exist commercial systems that utilize finite-deposition (FD) techniques that insert a continuous fiber braid into certain layers of the composite product. One of these machines, (known as the Mark Forge), has the fiber being introduced into the composite through the nozzle and a saw-like mechanism cuts the long fiber after it is extruded between layers. This method does not produce products with fibers homogenous through the entire product. As a result, traditional Laminate-Composite-Theory (LCT) does not apply to these composites without implementing further modifications for this inconsistency. The continuous fiber samples showed that fiber orientation had a vast effect on mechanical properties. A well oriented composite notably outperformed other fiber orientations with a drastic drop in Young’s modulus even with slight misalignment in fiber direction, but also resulted in brittle responses which may not be preferable. LCT is applied using the simulation software ANSYS workbench. It was found that the fiber orientation can cause a decrease in both the Young’s modulus and the maximum stress by over %66. The results showed considerable correlation for each orientation and can be used as an accurate predictor of mechanical characteristics for 3D printed continuous fiber composites.