Tolerance driven lightweight design and interface robustness of multi material aircraft horizontal tail structures

This study addresses the challenge of balancing weight reduction with stiffness in aircraft horizontal tails by proposing a multi-material design strategy combining carbon fiber reinforced polymer (CFRP) spars, closed-cell foam cores, and aluminum alloy joints. A three-dimensional nonlinear finite element model was developed to quantitatively assess how manufacturing tolerances—specifically variations in adhesive layer thickness and foam core density—affect interfacial mechanical performance. The co-optimized structure achieved a single-wing mass of 17.8 kg, representing a 32% reduction compared to conventional all-metal designs, while limiting the maximum displacement to 188.8 mm. Sensitivity analysis revealed that a 0.2 mm decrease in adhesive thickness increased peak interfacial shear stress by 22%. Monte Carlo simulations identified adhesive thickness variability as the dominant factor, contributing 64% of the variance in overall displacement. Robustness optimization, incorporating ± 45° ply reinforcement and tolerance-aware design, reduced the standard deviation of displacement by 50% and increased the transverse shear modulus by 17.3%. Validation tests on scaled prototypes demonstrated that a gradient density compensation strategy reduced displacement variability by 41%. The calibrated finite element model showed strong agreement with experimental data, yielding a coefficient of determination (R2) of 0.96. This work establishes a process-structure-property framework to support the reliable design of multi-material aerospace structures, though the findings are based on a scaled prototype and specific material combinations, indicating a need for validation at full scale and with other material systems.