INTRODUCTION

This Chapter is intended to give an insight into the practical considerations associated with the failure of FRP materials and/or structural components. From this, it will be appreciated that one of the major considerations is the definition of “failure” and, consequently, this can differ depending upon the intended use of the component. From the marine industries’ point of view “failure” of a laminate must be the initial surface fracture that would permit moisture penetration which, if not satisfactorily dealt with, will lead to subsequent deterioration of the laminate.

From the above, it will be appreciated that identifying the individual types of failure is only one of the practical considerations and unless accompanied by adequate repair procedures, the structural integrity of a component cannot be reinstated.

Prevention of “failure” can generally be taken into consideration in the design and fabrication process. Therefore, details of precaution against failure for laminates and hull structures have been included in this Chapter.

GEL COAT FAILURE

The gel coat should be of a uniform thickness throughout the surface of the mould. A gel coat of uneven thicknesses, or where the catalyst has been poorly mixed, will cure at different rates over its surface causing stresses which could lead to crazing and also give a patchy appearance. A very thin gel coat may not cure correctly and can result in attack when the resin for the back-up reinforcement is applied, leading to the possibility of gel coat wrinkling. Thixotropic gel coats minimise this occurrence.

A Barcol hardness indicator should be used to ensure that the gel coat resin has correctly cured after demoulding. The best way of examining the gel coat is visually.