Rigidization capacity and folding behavior of variable stiffness composite skin for inflatable lunar habitats

Abstract

Lunar construction is challenged by harsh environments and limited resources. Inflatables, with their inherent adaptability, offer promising solutions. This study introduces rigidizable inflatable lunar habitats using silicone-coated aramid fabric (SC-AF) as restraint layer and shape memory polymer (SMP) for rigidization. SC-AF exhibits excellent mechanical stability, folding capability, and tear resistance. After one fold, stiffness dropped by 17 % with negligible strength loss. X-ray micro-computed tomography (μCT) analysis revealed fiber deformation, misalignment, and coating micro-cracks, while fiber integrity remained almost intact. After 500 folds, stress dropped 19 % and stabilized after 10,000 cycles. Even after 50,000 folds, the material retained 29 % of its original strength without major fiber rupture, confirming Kevlar’s toughness. Practical applications involve fewer folds and less repetitive angles, allowing for a 20 % design safety margin. A theoretical dual-layer beam model evaluates equivalent stiffness based on material stiffness and thickness ratios, offering design limits and guidelines for rigidization and vibration control. For the SMP used, a thickness ratio of 0.02 or 1 is recommended, not exceeding 5. Rigidization capability should align with structural load-bearing requirements. This study integrates analytical, experimental, and numerical methods to advance high-strength restraint materials, examines folding-induced performance changes, and establishes design principles for SMP-based variable stiffness applications.