Experimental characterization and scaling of flexural rigidity in sewn multilayer structures

Sewing is one of the established methods used to fabricate and assemble multilayer insulation (MLI) blankets for aerospace applications, yet the resulting effective flexural behavior remains insufficiently understood. This study investigates the room-temperature, quasi-static flexural behavior of MLI blankets composed of aluminized BoPET radiation shields and polyester net spacers across structural configurations of 2, 6, 12, and 24 layers. A full factorial design was employed to evaluate the influence of the number of layers, stitch density, needle thread tension, and needle foot force. Statistical analyses demonstrated that the number of layers is the dominant factor governing flexural response. Among the sewing parameters, needle thread tension was associated with modifications in bending length, while needle foot force primarily affected local compaction. The scaling behavior suggests a provisional transition region in bending resistance, possibly within the 6–12layer range, under the tested conditions. Below this range, the assembly exhibits a lower scaling exponent consistent with weaker interlayer constraint, whereas thicker assemblies show a steeper stiffness increase, indicating enhanced constraint. In contrast, bending length increases uniformly due to its simultaneous dependence on stiffness and mass. Continuous piecewise power-law regression provided a better statistical description of the scaling behavior than conventional single-slope models, reducing the residual sum of squares (RSS) from 2.43 to 1.764 and yielding a lower AICc value. These findings provide a quantitative description of the effective cantilever flexural response of sewn multilayer assemblies at a fixed specimen width under the tested laboratory conditions, offering a basis for manufacturing quality control during handling and assembly.