Axisymmetric model that incorporates mesoscale effects for precise prediction of fiber strain in dome part of Type 4 tanks

The purpose of this research is to improve the accuracy of burst strength prediction using a simple model in order to find optimal tank design specifications. To improve the conventional axisymmetric model of Type 4 tanks in terms of the strain along the carbon fiber direction in the dome part, we incorporated mesoscale effects into the constitutive law for an axisymmetric orthotropic continuum model. We added three mesoscale effects that arise from the geometrical nonlinear motion and local strain increase of fiber bundles, namely the out-of-plane curvature effect, the in-plane rotational motion effect, and the crimp effect. The influences of these effects on the prediction accuracy of fiber-direction strain in the carbon-fiber-reinforced plastic layers of the axisymmetric model were quantitatively verified via comparisons with a mesoscale analysis, in which the mesoscale structure of fiber bundles was accurately modeled, and an internal pressure burst experiment on a small test tank, especially in the dome part. The strain obtained using the conventional model was three times higher than the experimental measurements near the equator, whereas that obtained using the proposed formulation was consistent with the measurements. Due to large errors in the dome section, optimal design using the finite element method was difficult, but the use of a high-precision axisymmetric model made it possible. Linear elastic analysis showed an error of approximately 10 % in the strain evaluation value in the nonlinear region on the high-pressure side, which is considered to be sufficiently accurate for application to design problems. • To improve the axisymmetric model of tanks in terms of the strain in dome part. • To incorporated mesoscale effects for an axisymmetric orthotropic continuum model. • To verified via comparisons with a mesoscale accurately modeled analysis. • The prediction accuracy was verified through experiments in a small test tank.