Thick laminates quality for ship design

Abstract

This paper draws attention to the quality problems encountered during the curing of thick structural thermosetting composites for naval use. For example, during curing thermal gradients and internal stresses are generated, leading to several imperfections (bubbles, fi bre waviness, etc) and, therefore, decreasing the quality of the composite. The fi rst part of the paper presents experimental results about material quality description. In particular, gradients of properties (degree of cure, cure shrinkage, elastic modulus) are clearly established within the composite and their dependency to the cure is presented. In the second part, a numerical tool that couples mechanical, physical and chemical phenomena, and devoted to industrial software, is proposed for cure simulation. The fi rst fi nite element modelling (FEM) results are presented and compared with experimental data of the cure. Thermal load is an important factor for thick thermosetting laminates quality, since the coupling effect between the thermo-activated and exothermal behaviour for thermosets becomes more pronounced with mass effect. Finally, while waiting for complete developments of such simulation tools of the curing process, the best advice for thick laminates manufacturers in order to improve the quality is to slow the cure cycle as the thickness increases.