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, fibre waviness, etc) and, therefore, decreasing the quality of the composite. The first 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 first finite 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.

Keywords:

• Epoxy
• cure modeling
• exothermic behavior
• shrinkage
• coupling
• carbon fibre
• microbuckling
• thick laminate

Additional information

Notes on contributors

C Jochum

Christian Jochum is Associate Professor of Mechanical Engineering and Materials Science at the Ecole Nationale Supérieure des Ingénieurs des Etudes et Techniques d’Armement in Brest, Brittany, France. Previously, he worked for several years as the head of the research department for the French supplier of track maintenance and construction equipment. Christian received his PhD degree with Honours from the University of Metz, Lorraine, France, in 1999 and is a member of the French Association of Mechanics.

J -C Grandidier

Jean-Claude Grandidier is Professor of Mechanical Engineering and Materials Science at the Ecole Nationale Supérieure de Mécanique et d’Aérotechnique in Poitiers, France. He is a member of the French Association for Composites Materials and of the board of directors for the French Association of Mechanics. Jean-Claude received the PhD degree with Honours from the University of Metz, Lorraine, France, in 1991.