Lattice structures by wire arc additive manufacturing: Design, manufacture, properties, applications, and challenges

Wire arc additive manufacturing (WAAM) is emerging as a scalable route for fabricating large-scale, coarse, strut-based metallic lattice structures that are difficult to produce within a typical laser-based powder bed fusion build-volume and powder-removal constraints. Given the rapid growth of this field, a systematic review is needed to consolidate current progresses and clarify barriers to the engineering adoption. This review examines WAAM lattice structures across slicing and toolpath planning, fabrication strategy, lattice design, fabrication quality analysis, mechanical performance, finite element modelling, applications, and standardisation. Existing studies have demonstrated mainly strut-based lattices in steels, aluminium alloys, titanium alloys, and copper-based alloys, with mechanical performance evaluated through tensile, compression, bending, and hardness testing at both strut and lattice scales. Finite element models can capture case-specific stress and thermal trends, but their predictive accuracy remains limited by nominal digitally-designedgeometry, simplified constitutive behaviour, insufficient node morphology, and weak thermal-history coupling. Demonstrated and prospective applications include civil construction, aerospace, marine engineering, and energy absorption. However, broader implementation is still constrained by immature lattice-aware slicing, gravity-induced strut instability, node control, restricted topology diversity, and inconsistent terminology. Mechanical testing should draw on existing additive manufacturing, cellular-metal, tensile and bending standards, but these frameworks must be adapted before they can serve as qualification protocols for WAAM lattices.