Edge-protected flexible capacitive strain sensing with orthogonal strain-pressure decoupling under confining pressure

To achieve accurate measurement of true large strains on the inner bore surface of solid rocket motor grains under confining pressure, this paper proposes a mechanism-constrained semi-empirical engineering method. The method targets a flexible capacitive large-strain sensor based on dispersed micro/nano conductive materials. It improves strain transfer efficiency through edge-structure optimization, establishes a multi-factor coupling model that simultaneously considers circumferential strain, axial strain, and pressure loading, and employs an orthogonal dual-sensor configuration to decouple pressure interference. On this basis, the effectiveness of the proposed method is validated through cold gas pressurization tests in conjunction with digital image correlation. The method can effectively isolate the electrical signal interference induced by confining pressure, thereby obtaining the true strain response of the grain under cold pressurization conditions. This study offers a new technical approach for health monitoring of soft-propellant grain structures under complex loading conditions, and furnishes the essential methodological basis and data support for the engineering extrapolation from sensor-level calibration to motor-level in-situ measurement.