Experimental method and numerical simulation demonstrate non-linear axial behaviour in composite filament wound pressure vessel due to thermal expansion effect

•Non-linear axial behaviour at the beginning of pressurisation in hydrogen tank.•X-ray method was used in order to investigate the presence of gap around dome area.•Gap effect on mechanical behaviour was investigated by DIC and 3D FEM.

The aim of this study is to understand the non-linear axial behaviour at the beginning of pressurisation in composite pressure vessel made by filament winding technique. X-ray method was used in order to investigate the presence of gap around dome area. This gap induced by debonding between composite shell and metallic boss during cooling stage of curing process due to different thermal expansion of pressure vessel components. Then, gap effect on mechanical behaviour was investigated by digital image correlation (DIC) and 3D finite element method (3D-FEM). We found that this effect induces local bending on dome area and induce a nonlinear behaviour response in axial direction at the beginning of internal pressure loading. In addition, a degree of nonlinearity depends on debonding length.Acoustic emission (AE) activity confirm this assumption since typical recording of AE signal represented a high duration, rise time and absolute energy but low frequency content which is correspond to the friction of contact surfaces.