A Review of Internal Structures in Additively Manufactured Turbomachinery Blades: Classification and Effects on Key Blade Characteristics

Additive manufacturing has become an important technology for turbomachinery blades because it enables lightweight components of high geometric complexity and allows the external shell and internal infill to be designed separately. However, published studies on blade internal structures remain fragmented because different works consider different cell types, materials, optimization formulations, and evaluation criteria, which complicates cross-study comparison. This review synthesizes 47 sources and classifies internal structures according to the method of geometric definition, distinguishing 2D parametric structures (class A1), 3D parametric strut-based and TPMS-based structures (class A2), free-topology structures obtained by topology optimization or generative design (class B), and hybrid structures combining parametric infill with free topology (class AB). Comparative analysis based on normalized data extracted from 17 studies is used to examine the effects of these structure classes on natural frequencies, stress state, thermal state, and fatigue life. The review is complemented by a structured study-by-study summary, which systematizes the studies used in the review discussion in terms of component type, material, additive-manufacturing process, internal-structure class, analysis method, investigated indicators, main results, and limitations. The available evidence indicates that class A1 structures are used mainly for mass reduction in narrow internal cavities, class B structures are especially effective for targeted material redistribution and often provide the largest increase in lower natural frequencies, whereas TPMS-based structures appear particularly promising for thermal-state-related applications. At the same time, fatigue life and manufacturing accuracy remain among the least studied and least experimentally validated characteristics.