Fabrication of advanced hybrid composite sandwich panels : testing and simulation

Abstract

One of the leading fiberglass boat manufacturers in Malta, Buccaneer Boats Ltd., currently makes use of the traditional hand layup in order to build fiberglass boats of high quality. This process has been proved to produce good quality laminates, but new processes such as vacuum bagging, led to further improvements in the laminate quality. The laminates produced with the vacuum bagging technique lack the required stiffness, therefore with the addition of a foam core between two fiberglass outer skins the stiffness of the laminate is increased. This method may reduce and even eliminate the need for the heavy and bulky stiffeners used with the single skin hull and deck construction. These new panels are called hybrid composite sandwich panels. This research project aims to introduce the vacuum bagging as a manufacturing process to fabricate both single skin and the new hybrid composite sandwich panels, to determine their properties, to evaluate the effectiveness of the vacuum bagging process and to detennine the increase in stiffness brought about by the addition of the foam core material. Samples using the current boat building layup sequence as used by Buccaneer Boats Ltd., were fabricated using the hand layup method and then by the vacuum bagging process. Testing was done in accordance to ISO and ASTM standards to determine the improvement in properties achieved by the new process. Sandwich panels were designed according to the relevant ISO standard for sandwich hull constructions; panels were fabricated using the vacuum bagging technique; then these were tested to characterize the relevant panel properties for flexure and shear. A mathematical concept model was also developed to predict the properties of the composite laminates and also for the sandwich panels. The results obtained show a good agreement of the theoretical data to the experimental data. The findings have clearly established that the new hybrid composite sandwich panels offer a better alternative to the single skin construction due to improved stiffness, overall mechanical properties and reduced weight.