A modified specimen holder for cone calorimeter testing of composite materials to reduce influence from specimen edges

ISO 5660-1 specifies the cone calorimeter method for characterizing the ignition andsurface burning behavior of materials. The specimen is irradiated through a squareopening in the frame of the specimen holder. The frame is intended to protect theedges of the specimen from irradiation but covers the edges with only a few mm. Intests with products such as composite laminates and sandwich wall panels, the pro-duction of pyrolysis gases from the edges and, in many cases, burning have beenobserved. Early contribution from the edges in the test is not representative for sur-face burning. A modified specimen holder was developed with a larger specimen sizeto allow better protection of the edges. The opening for exposure to irradiance ofthe retainer frame is circular and of the same area as that of the original frame. Thedistance between the exposed surface and the specimen edges is larger in order toprevent early exposure of edges. Tests using the standard specimen holder resultedin pyrolysis and burning from edges that took place outside of the specimen holder.Comparative tests using the modified specimen holder showed that it prevented theexposure and pyrolysis from edges for an extended time. However, the influence onignition time and peak heat release due to the increased size of the modified speci-men holder has not been characterized fully, and test results should not be used fordirect comparison with those of the standard holder.