Objectives  As composite materials have varied internal structures, an in-depth analysis of the damage mechanisms of their component materials can provide a research foundation for the ultimate strength analysis of composite stiffened panels.

  Methods  The microscopic, mesoscopic and macroscopic mechanical analyses of marine glass fiber reinforced plastic (GFRP) composite stiffened panels are carried out using a multi-scale approach. Microscopic and mesoscopic representative volume element (RVE) models of chopped strand mat (CSM) and woven roving (WR) materials are established, and the macroscopic equivalent stiffness is obtained by homogenizing the RVE models. The ABAQUS VUMAT subroutine is used to code the progressive damage evolution model of the composite materials to derive the damage evolution mechanism of the microscopic and mesoscopic models respectively. The equivalent strength of macroscopic laminates is also obtained.

  Results  The multi-scale approach can be used to accurately evaluate the macroscopic mechanical properties of composite materials, and the ultimate strength of composite stiffened panels is mainly determined by fiber bundle failure.

  Conclusions  The obtained macroscopic material parameters can be used to calculate the ultimate strength of composite stiffened panels, while the parametric study of the mesomechanics of composite materials can provide an analysis tool for investigating the influence of material processing technology.