Mechanical properties and hot forming potential of micro-perforated titanium sheets for laminar flow control structures

This study investigates the tensile behavior and microstructural evolution along manufacturing stages of commercially pure titanium grade 2 sheets with laser-induced micro-perforations, developed for application in hybrid laminar flow control (HLFC) aerospace structures. Micro-perforated specimens with two different pitch configurations were tested in multiple directions relative to the rolling direction to evaluate the influence of hole density and crystallographic texture on mechanical properties. Microstructural analysis via EBSD revealed a typical recrystallized α-phase structure with marked crystallographic texture leading to orientation-dependent deformation behavior. The presence of micro-perforations resulted in a moderate decrease in ductility, with strength largely retained across directions, particularly for micro-perforation pattern with 1.0 mm pitch. Fractographic analysis confirmed ductile transcrystalline fracture mechanisms, with dimple structures evident in ligament regions between hole lines. Additionally, the hot forming of micro-perforated sheets into a complex HLFC demonstrator geometry at 715 °C caused noticeable grain coarsening and changes in micro-texture. Mechanical testing post-forming revealed a reduction in both strength and fracture strain, attributed to thermal oxidation and microstructural evolution. Nevertheless, the mechanical properties after hot forming could be approximated using proportional reductions from room temperature data, with deviations within 5%. These findings demonstrate that micro-perforated titanium grade 2 retains favorable mechanical properties under HLFC-relevant manufacturing conditions, supporting its use in next-generation aircraft structures.