Tension relaxation during the NOL ring winding process based on a novel tracking element method

The NOL ring is employed as a specimen to examine the properties of filament-wound composites, with its winding tension playing a pivotal role in determining the performance of the resultant wound products. Traditional methods used for modeling the winding process have several disadvantages, including inaccuracies in setting the tension and difficulties in controlling the thickness of the wound layers. To address these limitations, utilizing the response mechanism of the tracking element method, a precise three-dimensional (3D) winding finite element model of the NOL ring is constructed. Adopting a wireless film pressure testing system to dynamically measure interlayer pressures, improved the precision of our experimental results by decoupling factors affecting tension relaxation and focusing on the structural relaxation characteristics of winding tension in composite materials. Experimental results demonstrate that, using this model, the prediction error for the radial stress on the mandrel surface is only 6.03%, which is substantially lower than that of the conventional models (16.72%). In addition, the model is used to investigate the stress transfer mechanisms in the radial/circumferential directions of the winding layers on a macroscopic scale. Finally, it is demonstrated through examples that this model can also achieve equal residual tension through optimization, which is expected to improve the structural efficiency of wound products.