Micro-scale tests such as Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) are used to determine key resin and additive characteristics, including the thermal decomposition temperature and the energy of decomposition. Understanding these characteristics allows manufacturers to develop different candidate FRP composites (material systems) based on quantified data. The bench-scale test Cone Calorimeter (Cone, ASTM E1354) can then be used to measure key material system characteristics such as time to ignition, burn duration, heat release rate per unit area (HRRPUA) and smoke production rate (SPR). The performance of candidate FRP composites can then be evaluated in terms of these characteristics.

An important attribute of the Cone is the ability to change the thermal insult (incident heat flux) applied to specimens. This allows the Cone to “scale” – or approximate the thermal insults of intermediate-scale and full-scale tests. By matching the thermal insult of a given test, characteristics such as HRRPUA and SPR can be used to predict behavior in these larger scale tests. These predictions are typically based on correlations and/or simple empirical models. It is important to understand that the Cone provides key understanding of material system behavior but does not provide complete understanding of component or assembly behavior.

Component and assembly performance depends not only on material system performance but also on the geometrical integrity of the component or assembly. Geometrical integrity is demonstrated by the component or assembly parts working together to maintain geometrical stability while under thermal insult (fire exposure). A key part of maintaining stability is the use of material systems which limit fire spread when either the component or assembly is exposed to fire. This is the basis of how the Cone can be used to predict behavior in larger scale tests. Using the Cone to predict intermediate-scale and full-scale behavior limits the number of tests that need to be run to demonstrate performance requirements of fire regulations.

A Closer Look at One Industry

As an example, let’s consider FRP composites for building construction. The relevant fire regulations are the International Building Code (IBC) as amended locally by states and cities in the United States. The IBC 2009, IBC 2012 and IBC 2015 all have specific reaction to fire performance requirements for FRP composites. No specific FRP composites fire performance requirements for fire resistance are written into the IBC at this time. Fire resistance of FRP composites and their assemblies is handled consistently with other materials such as wood, metal and concrete. The way roofing performance of FRP composites and their assemblies is handled is consistent with other materials.