The research, published as an open-access paper in the International Journal of Aeronautical and Space Sciences, simulated a 50.8 millimeter hailstone, the classic two-inch benchmark of aviation hail threat models, slamming into a radome modeled on the Airbus A320neo at a combined velocity of roughly 240 meters per second, the speed of a typical cruise condition. The team, led by Anand Pai with co-authors including P. K. Sowmya, Khushhali Chaudhary, Suhas Yeshwant Nayak, Chandrakant R. Kini and B. Satish Shenoy, compared two industry-standard fiber-reinforced polymer systems: glass fiber-reinforced polymer, or GFRP, and Kevlar, or p-aramid, fiber-reinforced polymer, known as KFRP. The verdict was unambiguous. The KFRP radome limited peak deformation to 8.1 millimeters, an 18 percent reduction compared with the 9.88 millimeters suffered by the GFRP variant, while weighing about 19 percent less.

The stakes are far from academic. The researchers compiled a survey of documented hailstone strikes on commercial aircraft over the past decade, and the record shows a rising frequency of encounters, a trend the authors attribute to the growing incidence of severe convective weather and the continued expansion of global air traffic. Hailstones routinely strike the nose cone, fuselage, wing skins, leading edges, control surfaces, engine nacelles and fan blades. The radome is particularly exposed because of its forward-facing geometry, and the minimum skin thickness requirements imposed to protect it carry a real weight penalty, one that matters acutely for smaller jets where every kilogram affects performance and fuel burn.

Modeling a hailstone is deceptively hard. Natural hail is polycrystalline ice, a layered, anisotropic material riddled with air and water pockets, and its mechanical behavior swings dramatically with strain rate. At the high strain rates of 100 to 300 per second typical of these impacts, ice transitions from ductile to brittle failure, yet high-speed imaging shows it retains residual strength through fragmentation and axial splitting even after damage initiates. Its compressive strength and hardness can climb by more than 300 percent as temperature falls from minus 15 to minus 50 degrees Celsius. The team represented the projectile using Smoothed Particle Hydrodynamics, a mesh-free method that sidesteps the severe mesh distortion that cripples traditional Lagrangian finite element approaches during extreme deformation. The hailstone was discretized into 67,731 particles of one millimeter each, governed by a bilinear isotropic constitutive model that captures the critical moment when the ice’s deviatoric stress vanishes at the failure threshold and the projectile begins to behave like a fluid.

The radome itself was built with equal care. The 7.5 millimeter skin was assembled from thirty discrete plies of 0.25 millimeters each in a symmetric [0/90]15 stacking sequence of 2 by 2 twill weave fabric. Rather than plugging in generic material cards, the researchers derived the effective orthotropic properties through a multi-scale homogenization workflow: representative volume elements of the unidirectional yarn architecture and the bidirectional woven architecture were simulated in ANSYS Material Designer, using manufacturer data for Kevlar 2200 aramid fibers with a Young’s modulus of 108 gigapascals and EC11 204 E-glass fibers at 72.4 gigapascals, both embedded in an epoxy matrix. The resulting laminate definitions were then exported into ANSYS Explicit Dynamics, where the coupled SPH-finite element framework ran the impact scenarios over a 100 microsecond window.

The simulation reproduced a two-stage impact response well known from experimental literature on flat composite panels: a rapid loading stage in which stress and deformation climb to a peak, followed by a rebound stage as the projectile fragments and the stress decays. On the curved radome geometry, the two materials diverged after about 40 microseconds. Up to that point their deformation histories were nearly indistinguishable, but the GFRP shell then deformed more steeply toward its larger final value, while the KFRP laminate held a more stable late-stage profile. Contact stress told a complementary story. The KFRP radome reached a higher peak stress of roughly 1581 megapascals at about 60 microseconds, versus about 890 megapascals at 70 microseconds for GFRP, indicating a stiffer, more localized response that accelerates hailstone fragmentation and spreads the debris tangentially along the radome’s curvature, a phenomenon the authors call geometric shedding.

Energy accounting reinforced the picture. Both simulations began with an identical projectile kinetic energy of 1925 joules, and total energy was conserved throughout, with hourglass energy held below 2 percent of peak internal energy, satisfying standard explicit dynamics stability criteria. But the KFRP radome accumulated more internal energy and showed a sharper decay of the projectile’s kinetic energy, signatures of enhanced momentum dissipation through multi-axial matrix shearing and plastic work. In other words, the aramid architecture does not merely deflect the blow; it absorbs and dissipates the impact energy more effectively across the convex surface of the nose cone.

Perhaps the most technically interesting contribution is the ply-by-ply failure analysis. Because global mechanical metrics poorly capture the directional nature of composite damage, the team implemented a sequential explicit-to-implicit mapping: deformation states extracted at 40, 60, 80 and 100 microseconds from the explicit solver were transferred into a static implicit environment, where the anisotropic Tsai-Wu failure criterion yielded an Inverse Reserve Factor for individual plies. An IRF at or above 1.0 signals the onset of material degradation. The results exposed a fundamental difference in damage character. In the GFRP radome, elevated failure indices spread diffusely, with the rear ply reaching IRF values up to 3.30 across wide, unconfined contours, a pattern that raises the risk of widespread micro-cracking, shear failure and interlaminar delamination. The KFRP radome, by contrast, confined its most severe indices, which climbed as high as 11.79, to a narrow zone at the impact apex, while the mid-plane plies stayed comparatively protected. Damage containment, not merely damage resistance, emerged as the Kevlar laminate’s decisive advantage, preserving the load-bearing capacity of the surrounding shell and the radar instruments behind it.

To bridge the gap between idealized single impacts and operational reality, the researchers also ran a cluster scenario of five concurrent 50.8 millimeter hailstones spaced 60 millimeters apart, extending the simulation to 5 milliseconds to capture staggered strikes and shockwave interactions. The result was a wider concave indentation with surface cratering across the central radome region, a damage envelope that closely resembles photographic evidence of real hail damage on an operational Interjet A320 nose cone. That qualitative agreement, the authors argue, validates the framework’s ability to capture the momentum transfer required to produce macroscopic cratering. The team is candid about limitations: the bilinear ice model omits thermal effects and microstructural heterogeneity, and future work will add stochastic multi-impact scenarios and cohesive zone modeling to probe the interplay between intralaminar softening and delamination. Still, the message for aircraft designers is striking. A radome built from Kevlar rather than glass fiber could shed roughly 19 percent of its mass, about 114 kilograms in the modeled geometry, while deforming less, absorbing more energy and keeping damage tightly contained where it matters least to the aircraft’s survival.

Subject of Research: Computational simulation of hailstone impact response of composite aircraft radomes

Article Title: Dynamic Impact Response of Composite Aircraft Radomes Subjected to Hailstone Impact: A Computational Study

Article References: Pai, A., Sowmya, P. K., Chaudhary, K., Nayak, S. Y., Kini, C. R., & Satish Shenoy, B. (2026). Dynamic Impact Response of Composite Aircraft Radomes Subjected to Hailstone Impact: A Computational Study. International Journal of Aeronautical and Space Sciences. https://doi.org/10.1007/s42405-026-01308-2

Image Credits: AI Generated

DOI: 10.1007/s42405-026-01308-2

Keywords: aircraft radome, hailstone impact, Kevlar, GFRP, composite laminates, SPH, finite element analysis, Tsai-Wu failure criterion, aviation safety, explicit dynamics, impact damage, A320neo

Sandwich structures work much like an I-beam stretched into a panel: two stiff outer skins take bending stresses while a lightweight core holds them apart and resists shear. In civil engineering, this architecture promises high strength-to-weight ratios, built-in thermal insulation, and excellent energy absorption. Fiber-reinforced polymer face sheets add corrosion resistance, cutting maintenance and life-cycle costs compared with steel or reinforced concrete. Curved versions of these panels open additional design freedom for architecturally ambitious roofs and facades, yet their static bending behavior has remained surprisingly underexplored, with most prior research focused on vibration and aerospace applications.

The research team fabricated singly curved panels using vacuum infusion molding, a process that begins by cutting foam into an arc, wrapping it with a layer of ±45° glass-fiber fabric, and then sequentially assembling the bottom face sheet, internal web cores, and outer face sheet on a curved wooden mold before resin infusion. After eight hours of curing, the panels were demolded and trimmed. Three core configurations were compared: conventional polyurethane foam, grid-scored recycled PET foam, and recycled PET foam reinforced with a continuous lattice of glass fiber webs. Each panel had a span of 400 millimeters, a width of 200 millimeters, a 25-millimeter-thick core, and five ring webs spaced 200 millimeters apart horizontally.

Curvature proved to be a decisive variable. Panels were tested at three radii of 300, 580, and 1150 millimeters, corresponding to central angles of 60, 30, and 15 degrees. For the polyurethane foam series, the panel with the largest radius failed at 7.49 kilonewtons through brittle compressive fracture of the upper face sheet beneath the loading plate. Reducing the radius to 300 millimeters cut the ultimate load to 5.29 kilonewtons and the bending stiffness to 0.73 kilonewtons per millimeter, a 29.4 percent loss in capacity and a 26.3 percent loss in stiffness. Tighter curvature intensified membrane-bending coupling and radial compression, triggering premature debonding between face sheet and core before the panel could fully mobilize its bending resistance.

The grid-scored PET foam panels, in which load transfer relies on discontinuous resin-rich channels, fared worse under the same conditions. Their initial stiffness values of 0.66 and 0.77 kilonewtons per millimeter lagged well behind the lattice-reinforced equivalents, and stress concentrations at the resin columns, the foam-resin interface, and the face-core boundary interacted destructively during loading. At the smallest radius, interfacial delamination began at only 3.49 kilonewtons, and the panel ultimately failed at 4.37 kilonewtons before collapsing to 1.50 kilonewtons as shear cracks spread through the foam. The discrete grid could not bridge cracks or redistribute stress once local damage started, so degradation was rapid and brittle.

By contrast, the lattice-reinforced recycled PET foam panels delivered the best performance across every curvature. The largest-radius specimen reached an initial bending stiffness of 1.09 kilonewtons per millimeter and a peak load of 12.4 kilonewtons, while the moderate-radius panel achieved the highest ultimate load of the entire experimental campaign at 13.3 kilonewtons. Even the tightest-radius panel sustained 11.0 kilonewtons. Crucially, after the upper face sheet fractured in compression, the loads did not collapse entirely; they dropped only partially and then recovered, for example from 13.3 to 11.5 kilonewtons, because the continuous lattice webs acted as internal bridges that kept transferring load between the separated face sheets. Compared with the grid-scored design, ultimate loads rose by 71.5 to 151.7 percent.

Digital image correlation provided a strain-map view of these mechanisms in real time. In large-radius panels, strain concentrated in the upper face sheet under the loading plate, confirming compression-dominated failure. As radius shrank, shear strain localization migrated into the foam core near the load point and the face-core interface, signaling the shift toward debonding and core shear failure. The lattice-reinforced panels showed markedly more continuous strain distributions along the curved section than their grid-scored counterparts, evidence that the internal webs diffused stress, restrained local deformation, and delayed unstable crack propagation through the thickness of the core.

To go beyond what experiments alone could reveal, the team built a three-dimensional finite element model in ABAQUS incorporating Hashin damage criteria for the composite laminates, a crushable foam plasticity model with volumetric hardening for the PET core, and a bilinear cohesive zone model for the face-core interface. The simulations reproduced the measured stiffness and peak loads with errors below 10 percent, and predicted failure modes matched the laboratory observations, including interfacial debonding captured through cohesive damage variables. Deflection fields at a 4.0 kilonewton load level also agreed closely with the DIC measurements, validating the model as a trustworthy design tool.

The parametric study then isolated the levers that matter most. Raising the PET foam density from 80 to 150 kilograms per cubic meter increased ultimate load by 29.2 percent but bending stiffness by only 18.9 percent, because global stiffness is governed mainly by the axial stiffness and separation of the face sheets rather than the core. Fiber layup orientation strongly affected initial stiffness, with a (0°,90°) laminate reaching 2.15 kilonewtons per millimeter against 0.85 for an all ±45° stack, yet ultimate loads stayed within a narrow band around 13.7 to 14.1 kilonewtons. Lattice geometry emerged as the most powerful knob: thickening the longitudinal webs from 1.2 to 3.6 millimeters lifted ultimate load from 13.69 to 15.00 kilonewtons, and tightening longitudinal web spacing raised peak load to 16.43 kilonewtons, a gain of roughly half over the baseline configuration.

Across all variations, the dominant failure sequence remained interfacial delamination followed by compressive failure of the upper face sheet, but the lattice consistently delayed that sequence and preserved residual capacity afterward. The findings carry practical weight for sustainable construction: recycled PET foam diverts plastic waste, requires less production energy than traditional core materials, and adds thermal insulation, while GFRP skins resist corrosion and reduce reinforcement demands on existing structures. By demonstrating that a simple internal lattice transforms a recycled-core curved panel from brittle and debonding-prone into a progressively damage-tolerant structural element, the study offers designers a clear, simulation-backed recipe for lighter, greener, and more resilient civil infrastructure.

Subject of Research: Experimental and numerical investigation of the bending behavior, failure modes, and design parameters of curved GFRP sandwich panels with recycled PET foam cores and internal lattice reinforcement

Article Title: Bending behavior of curved sandwich panels comprising GFRP face sheets and recycled PET foam cores: Experimental investigation and numerical simulation

Article References: Xie, H., Man, J., Zhang, Z., Fang, H., Wang, Z., & He, P. (2026). Bending behavior of curved sandwich panels comprising GFRP face sheets and recycled PET foam cores: Experimental investigation and numerical simulation. Case Studies in Construction Materials, 25, Article e06525. https://doi.org/10.1016/j.cscm.2026.e06525

Image Credits: AI Generated

DOI: 10.1016/j.cscm.2026.e06525

Keywords: GFRP, recycled PET foam, curved sandwich panels, lattice reinforcement, bending behavior, face-core debonding, finite element simulation, Hashin damage criteria, digital image correlation, sustainable construction, foam core density, civil infrastructure