Additively manufactured materials: A critical review on their anisotropic mechanical properties and modeling methods

Additive manufacturing (AM) technology has attracted wide attention from various industries worldwide due to its ability to rapidly fabricate complex three-dimensional structures. Additively manufactured materials (AMMs, including metals, alloys, polymers, inorganic nonmetal materials, and composites) and structures are currently being applied in important fields such as aerospace, construction, and healthcare. However, AM technology still faces challenges, particularly the mechanical anisotropy of AMMs, which can hinder its further applications. Specifically, because of the layer-by-layer manufacturing process, AMMs inevitably possess numerous defects and heterogeneous microstructures, leading to unpredictable anisotropic mechanical behavior. Currently, there is a lack of comprehensive and in-depth views and comparison regarding the mechanisms of anisotropic mechanical properties and constitutive modeling methods for different AMMs. To fully exploit the advantages of AM technology in the design and manufacturing of complex structures, a thorough understanding of the anisotropic mechanical behaviors of different types of AMMs, as well as their mechanical anisotropy modeling and control methods is necessary. This article reviews and compares the mechanisms influencing the anisotropic mechanical behavior of various AMMs, as well as the research progress in developing their anisotropic constitutive models and control methods. This review also proposes future research directions, providing a reference for researchers and engineers to understand, apply, and continuously develop this field of study.