Design and optimization of compliant mechanisms for mechanical attachment systems

Abstract

Bistable compliant mechanisms offer a promising alternative to traditional fasteners and adhesives for mechanical attachment, enabling lightweight, reusable locking systems across diverse applications. This work presents two compliant locking mechanisms: one tool-less and in-plane for aerospace thermal protection systems, and another tool-actuated and out-of- plane for modular panel assemblies. The aerospace mechanism was prototyped in polylactic acid (PLA) and optimized using a hyperelastic solid model with a yield constraint, applying sequential sweeps of geometric parameters. The resulting design achieved a retention force of 53.41 N with a mass of 47.3 g and a 789 mm2 footprint, offering rapid tile exchange without adhesives. The modular panel system created a physical model inspired by industry needs and, separately, introduced an updated computational framework using particle swarm op- timization (PSO) coupled with FEniCSx simulations to enable multi-dimensional geometry tuning for material-dependent design. PSO-FEniCSx algorithm explored a three-parameter solution space, including band thickness, band angle, and side shuttle length, using a swarm of 16-particle’s evolving over 12 iterations. The best configuration, with band thickness “t” = 1.3 mm, band angle ”θ” = 78.85◦, and side shuttle length “ssl” = 29.66 mm, achieved a peak retention force of 66.33 N while remaining below the 95% yield stress threshold. Experimental validation confirmed that PSO accurately characterizes structures based on maximum force. However, it was found that the FEniCSx boundary conditions did not cor- rectly accurately represent deformation at the side walls during geometry transformation. To resolve this discrepancy, replacement of fixed conditions with a pin support is recommended. These results demonstrate that bistable compliant structures can be computationally opti- mized and physically tuned to meet application-specific requirements in both aerospace and architectural contexts.