FBG-Based Monitoring and Hailstone Impact Assessment of an SLM Lattice Leading Edge for Aircraft De-Icing Applications

Hailstone and soft-body impacts represent a critical threat to the structural integrity of aircraft leading edges, potentially compromising anti-icing system functionality and flight safety. This paper addresses the combined challenge of impact resilience and in-service monitoring for a novel Selective Laser Melting (SLM) lattice-core leading edge designed for subsonic aircraft de-icing applications. Three alloys-AlSi10Mg, AISI 316L, and Ti-6AI-4V-were manufactured and subjected to an explicit Finite Element Method (FEM) impact analysis using Altair Radioss with Smooth Particle Hydrodynamics (SPH) ice discretisation, covering hailstone diameters of 15-35 mm and velocities of 100-200 m/s. A complementary gas-gun experimental campaign, designed according to a Face-Centered Central Composite Design of Experiments, provided ground-truth damage data classified on a 0-3 scale and validated the numerical predictions. Fiber Bragg Grating (FBG) sensors, bonded on the external skin, were deployed as a dual-function sensing network: thermal cycling tests between -40 ° C and +50°C yielded temperature-wavelength-shift correlation coefficients above 99% for both AlSi10Mg and AISI 316L, while the same sensors captured deformation onset, post-impact damping, and residual strain during ballistic events with sub-millisecond resolution. AISI 316L exhibited no perforation across the full test envelope; AlSi10Mg reached skin breakage above ~170 m/s for diameters ≥ 25 mm.