Reduced weight makes use of fiber reinforced polymer composite desirable in maritime construction applications. Exterior ship surfaces in combustible materials are although not covered by fire safety regulations and their fire protection is therefore a key issue. This paper reports how SP FIRE 105, a standardized test method for testing reaction to fire properties of façade systems, was adjusted and used to evaluate the potential for fire growth on external combustible ship surfaces; in particular fiber reinforced polymer composite surfaces protected with active or passive measures. The trials show that the test method is highly suitable but that some adjustments could be made to reduce uncertainties; in particular to use a gas burner instead of a heptane pool fire source and to add a strong criterion for when to activate active measures. Further efforts should also be made to develop suitable performance criteria, which were suggested to be based on the produced heat and the gas temperatures at the top of the panel.
SUMMARY ISO 5660‐1 specifies the cone calorimeter method for characterizing the ignition and surface burning behavior of materials. The specimen is irradiated through a square opening in the frame of the specimen holder. The frame is intended to protect the edges of the specimen from irradiation but covers the edges with only a few mm. In tests with products such as composite laminates and sandwich wall panels, the production of pyrolysis gases from the edges and, in many cases, burning have been observed. Early contribution from the edges in the test is not representative for surface burning. A modified specimen holder was developed with a larger specimen size to allow better protection of the edges. The opening for exposure to irradiance of the retainer frame is circular and of the same area as that of the original frame. The distance between the exposed surface and the specimen edges is larger in order to prevent early exposure of edges. Tests using the standard specimen holder resulted in pyrolysis and burning from edges that took place outside of the specimen holder. Comparative tests using the modified specimen holder showed that it prevented the exposure and pyrolysis from edges for an extended time. However, the influence on ignition time and peak heat release due to the increased size of the modified specimen holder has not been characterized fully, and test results should not be used for direct comparison with those of the standard holder.
To reduce environmental impact and to manage weight in shipping and offshore, lightweight structures are becoming increasingly important. A critical issue for loadbearing structures is their structural fire integrity. It is generally evaluated by loaded furnace fire resistance tests based on ISO 834. As part of the EU project BESST, a series of such tests were performed with typical lightweight fiber reinforced polymer (FRP) composite sandwich structures. The purpose was to determine whether structural fire integrity is sensitive to the design load, design method and safety factor against buckling. In particular was examined whether the temperature at the interface between the exposed laminate and the core is critical for structural integrity and how it depends on the applied loading. Independence of the applied load would make performance solely a matter of heat transfer, which would significantly reduce necessary testing. The tests were carried out with starting point in an insulated sandwich panel system, certified as a 60 minute Fire Resisting Division (FRD-60) for high-speed craft in accordance with the Fire Test Procedures (FTP) Code. The structure consisted of 1.3 mm glass fiber reinforced polyester laminates surrounding a cross linked PVC foam core called Divinycell H80 (80 kg/m3). It was constructed for a 7 kN/m design load, which is the loading applied in the FTP Code furnace test for high-speed craft. Hence, with a conventional safety factor against buckling of 2.5 it was designed to resist a critical load of 17.4 kN/m. With basis in this design, tests were performed with structures where the thickness of the laminates or core had been altered and with adjusted safety factor against the applied loading. In addition, a test was performed with a stiffened panel. Firstly it was noted that 60 minutes of fire resistance was not achieved in most of the tests, which was a consequence of an alteration in the FTP Code test procedures. The FRD-60 structure used as starting point was certified before the 2010 edition of the FTP Code was ratified. This harmonized the test procedure between laboratories and gave a slightly tougher temperature development than when the structure was certified. However, the test results are still valid and show a small variation in the time to failure in the tests with unstiffened sandwich structures, ranging between 51 and 58.5 minutes. Changing the safety factor from 2.5 to 1.5 resulted in a relatively small decrease in time to failure of 3 minutes. The stiffened test showed that structural resistance is better achieved by use of stiffeners than by thick laminates. Furthermore, applying this as a design principle and using a safety factor of 2.5 leaves a test variation between 55 and 58.5 minutes. The temperature at the exposed laminate-core interface was quite similar in the tests at the time of failure. This excludes the test when the laminate thickness was increased as a measure for structural improvement. In conclusion, the test series shows that fire resistance bulkhead testing of insulated FRP composite panels can be simplified and does not have to be performed with varying design loads. To achieve conservative evaluation, a design concept should be evaluated by testing the panel designed for the highest applicable load level, not by testing a weak panel at 7 kN/m loading. This applies to non-stiffened solutions.
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