Thermal Response Parameter Research Articles

Modeling the response of composite beam–slab assemblies exposed to fire

This paper presents the development of a three-dimensional nonlinear finite element model for evaluating the response of composite beam–slab assemblies subjected to a combination of gravity and fire loading. The behavior of typical beam–slab assemblies with different shear connection types (welded–bolted shear tab and all-bolted double-angle connection), exposed to different fire scenarios, was modeled using ANSYS. The finite element model accounts for temperature dependent thermal and mechanical properties of constituent materials, connections, and composite action. Transient time domain coupled thermal-stress analysis is performed to obtain the temperature distribution and deformation response of the composite beam–slab assembly. The finite element model is validated by comparing the predicted and measured thermal and structural response parameters of three composite beam–slab assemblies tested under fire conditions. The comparisons show that the proposed model is capable of predicting the fire response of beam–slab assemblies with good accuracy. Research from the analysis clearly shows that the composite action between the beam and slab significantly enhances the fire performance of composite beam–slab assemblies. It is concluded that the proposed finite element model could be used as a feasible tool to evaluate the fire response of composite floor systems.

Determination of characteristic parameters for the thermal decomposition of epoxy resin/carbon fibre composites in cone calorimeter

Present study concerns to the thermal degradation of two carbon fibre/epoxy composites, which differ by their volume fractions in carbon fibre (56 and 59 vol%), investigated in cone calorimeter (under atmospheric condition with a piloted ignition). In order to study the influence of the carbon fibre amount on the composite thermal decomposition, the cone calorimeter external heat flux was varied up to 75 kW m−2. Thus, main parameters of the thermal decomposition of two different composites determined were: mass loss, mass loss rate, ignition time, thermal response parameter, ignition temperature, critical heat flux, thermal inertia and heat of gasification. As a result, when carbon fibre fraction decreases from 59 to 56 vol%, an increase of the thermal parameters was observed: 14–18 kW m−2 for critical heat flux, 370–435 kW s1/2 m−2 for thermal response parameter, 2.25–5.07 kW2 s m−4 K−2 for thermal inertia and 16–18 kJ g−1 for gasification heat. By analysing the mass loss rate evolutions, a four phases thermal decomposition mechanism is proposed. In the first phase, epoxy resin is cracked to form low molecular weight gaseous species and epoxy-derived compounds. For two next phases, the combustion of epoxy resin and liquor monomer solvent is observed that induces the formation of carbon char. In the last phase, char oxidation and carbon fibre decomposition are identified. Further, during the composite decomposition process, thermal behaviour of solid matrix is changed from a thermally thick material to a thermally thin one when sample is exposed at high external heat flux above 20 kW m−2.

Fast temperature sensing using changes in extraordinary optical transmission through an array of subwavelength apertures

A fast, sensitive temperature sensor using changes in extraordinary optical transmission (EOT) through an array of nanoholes in a metallic film with a monochromatic collimated light source is analyzed and experimentally demonstrated. The device is composed of a dielectric material in contact with a metallic film with an array of nanoholes, (25 arrays per chip were treated as a single sensor), on a glass substrate. Although the present experiment used a volume of water in a test cell to demonstrate the phenomena, there are many configurations that implement this technology in a variety of applications. The fast response of the device is expected because it measures the average temperature of a thin layer of the dielectric material directly above the nanoholes, ~100 nm. The thermal response parameter of the nanohole array sensing region is ~108 times smaller and orders of magnitude faster than that of the reference thermistor. The increased speed and sensitivity of the nanohole array temperature sensor over the thermistor is observed in the reported data. The configuration of this temperature sensor was used for simplicity and to demonstrate that EOT effects can be used for temperature sensing.

Inherent flammability parameters—Room corner test application

AbstractIt has been hypothesized that four parameters are solely responsible for a material's performance in a flammability scenario. This excludes effects of material physical integrity, i.e. melting, delamination, etc. They are (1) the critical heat flux below which piloted ignition cannot occur (CHF), (2) the ratio of heat of combustion to heat of gasification (HRP), (3) the thermal response parameter related to the thermal inertia and the ignition temperature (TRP), and (4) the available energy per unit area (AEP). The fire scenario controls the process by its initial heat flux and region of ignition. The hypothesis is applied to 54 tests of the ISO Room Corner Test to assess its validity. It is shown that these four parameters give good correlations in predicting the time to flashover and whether it occurs. In principle, different correlations could be developed for other scenarios of tests and fire configurations. Copyright © 2009 John Wiley & Sons, Ltd.

A theoretical basis for flammability properties

Theoretical formulations are presented for the fire growth processes under external radiant heating. They included ignition, burning and energy release rate, and flame spread. The behaviour of these processes with external heating is described along with the critical conditions that limit them. These include the critical heat fluxes for ignition, flame spread and burning rate. It is shown how these processes and their critical conditions depend on a limited number of properties measurable by a number of standard test methods. The properties include heat of combustion, the heat of gasification, ignition temperature and the thermal properties of the material. Alternatively, the properties could be related to parameters easily found from data; namely: (1) the critical heat flux (CHF) for ignition, (2) the slope of the energy release rate with externally imposed flux, defined as heat release parameter (HRP); and (3) the ignition parameter.. defined as thermal response parameter (TRP). It is further shown that the flame heat flux differences between small laminar flame ignition sources and larger turbulent flames can affect flame spread due to heat flux and ignition length factors. Finally, it is found that the critical energy release rates theoretically needed for ignition, sustained burning, and turbulent upward flame spread are roughly 13, 52, and 100kW/m(2), respectively, and independent of material properties.

Preliminary Thermography Studies for Quality Control of Concrete Structures Strengthened with Fiber-Reinforced Polymer Composites

Fiber-reinforced polymer (FRP) composites, in the form of pultruded laminates or built-up woven fabrics, are being used widely to strengthen existing concrete and masonry structures. The success of these materials in performing their intended functions depends, to a large extent, on how well they are bonded to themselves and to the substrate. There is a need for an efficient and reliable method to detect and characterize defects at the substrate interface and within multi-ply systems. Infrared thermography is well suited for this purpose because it is inherently sensitive to the presence of near-surface defects and can interrogate large areas efficiently. Before infrared thermography can be developed into a standard methodology, however, an understanding is needed of the effects of testing parameters and different types of defects. A multiyear study is under way to develop this understanding through the use of controlled-flaw experiments and finite-element modeling. This paper reports on the initial phases of this study. An experimental setup is described for measuring the emissivity of a carbon FRP composite and for obtaining a well-defined heat pulse. Good agreement was found between experimental thermal response parameters and those calculated from finite-element models of controlled-flaw specimens. This agreement provides assurance of the validity of parametric studies based on numerical simulations.

Ignition Properties of Fabrics

ASTM E2058 (NFPA 287) Fire Propagation apparatus was used to determine the Critical Heat Flux (CHF) and Thermal Response Parameter (TRPthin) of 10 fabrics by measuring time to ignition at different heat flux values. CHF values were in the range 15–25 kW/m2 and decreased with fabric areal density and cation content. TRPthin values expressed as areal density heat capacity ignition temperature above ambient were in the range 500–2439kW-s/m2. There was a reasonable correlation between the measured TRPthin values and the areal density of the fabrics examined in this study. Light areal density fabrics with low TRPthin values (≤ 1000 kW-s/m2) had high ignitions with the fast smoldering cigarette, while heavy areal density fabrics (≥ 1200 kW-s/m2) had high ignitions with the slow smoldering cigarette.

Flammability evaluation of clean room polymeric materials for the semiconductor industry

A new methodology, identified as the 4910 Test Protocol, has been developed to evaluate the fire propagation and smoke development behaviour of polymeric materials for use in clean rooms for the semiconductor industry. This paper reviews the scientific basis of the concepts and criteria contained in the 4910 Test Protocol. For the acceptance of polymeric materials, two criteria are used: (a) Fire Propagation Index (FPI) less than or equal to 6 (m s(-1/2))/(kWm(-1))(2/3) and (b) Smoke Development Index (SDI) less than or equal to 0.4 (gg(-1)) (ms(-1/2))/(kWm(-1))(2/3). Materials are tested in the ASTM E 2058 Fire Propagation Apparatus (previously identified as the Factory Mutual Research Flammability Apparatus). The Fire Propagation Index (FPI) is formulated from: (a) the Thermal Response Parameter (TRP), which relates the time-to-ignition to the net heat flux to the sample surface, and (b) the chemical heat release rate measured during the upward fire propagation in air having a 40% oxygen concentration to simulate flame heat transfer at large scale. The SDI is related to the smoke release rate and is obtained by multiplying the FPI value by the smoke yield. The smoke yield is defined as the ratio of the total mass of smoke released per unit mass of the vapours of the polymeric material burned. Small and large-scale fire test data have been included in the paper in support of the 4910 Test Protocol criteria. Highly halogenated and high temperature specialty polymeric materials and highly modified ordinary thermoplastics are found to satisfy the criteria.

Minimum Safe Distance from Pool Fires

Radiation heat transfer is a primary reason for Ž re growth. Experimental data are needed to clarify the ignition potential and time required to ignite a particular target second item. The concepts of critical heat  ux and thermal response parameter are important to the material ignition problem. The objective of the present contribution is to clarify these important radiant ignition concepts and to exemplify a range of realistic calculations related to real-world situations.

Characterization Of The Ignition Behaviour Of Polymers Commonly Used In The Automotive Industry

Ignition behavior of selected polymers, commonly used in the automotive industry. has been characterized by the maximum heat flux at which there is no ignition, defined as the Criticul Heat Flux, CHF, and by a combination of thermo-physical properties, defined as the Thermal Response Parameter (TRP). Polymers with high CHF and TRP values have high resistance to ignition. The ignition temperatures of the polymers appear to be about 10 % higher than their decomposition temperatures. The TRP values calculated from the thermo-physical properties of the polymers (ignition temperature, density, heat capacity, and thermal conductivity) are about 33 % lower than the experimental TRP values obtained from the measured time-toignition at various external heat flux values. Inclusion of bond energies and chemical nature of vapors in the TRP formulation is suggested. The CHF and TRP values of the selected polymers are comparable to the values for ordinary combustible materials, but are lower than the values for the highly thermally stable specialty polymers.

Modeling Of Sprinkler, Vent And Draft Curtain Lnteraction

The International Fire Sprinkler, Smoke & Heat Vent, Draft Curtain Fire Test Project organized by the National Fire Protection Research Foundation (NFPRF) brought together a group of industrial sponsors to support and plan a series of large scale tests to study the interaction of sprinklers, roof vents and draft curtains of the type found in large warehouses, manufacturing facilities, and warehouse-like retail stores. In conjunction with the large scale tests, NIST developed a numerical model based on large eddy simulation techniques, the Industrial Fire Simulator (IFS), that could be used to plan, analyze and supplement the test results. A series of bench scale experiments was conducted to develop necessary input data for the model. These experiments generated data describing the burning rate and flame spread behavior of the cartoned plastic commodity, thermal response parameters and spray pattern of the sprinkler, and the effect of the water spray on the burning commodity.

Ignition and Opposed Flow Flame Spread Using a Reduced Scale Attachment to the Cone Calorimeter

A reduced scale ignition and flame spread technique (RIFT) was implemented in the cone calorimeter test system to generate thermal and combustibility material response parameters normally associated with an intermediate scale test, LIFT. The magnitude of the parameters derived using RIFT compare favorably with those obtained using the standard LIFT apparatus. The results of the modified cone calorimetric system or RIFT can be used to generate more specific material combustibility characteristics associated with materials burning over time, helping to create and refine engineering models of solid phase combustion. When validated, such models would help us predict and control flame spread with more certainty.

Flammability Parameters of Materials: Ignition, Combustion, and Fire Propagation

In this paper, flammability parameters associated with the igni tion, combustion, and fire propagation processes and their usefulness for the development of fire resistant materials are discussed. The flammability param eters discussed are: (a) Critical Heat Flux (CHF) and Thermal Response Param eter (TRP), associated with ignition, (b) Heat Release Parameter (HRP) and Fire Propagation Index (FPI), associated with combustion and fire propagation.

Polymers and Composites- An Examination of Fire Spread and Generation of Heat and Fire Products

Fiber reinforced composite (FRC) materials are used extensively because of their favorable physico-chemical properties and high strength- to-weight ratio. The use of composites in Army vehicles as a means of decreas ing weight and enhancing survivability, without reducing personnel safety, has been under study for some time. Although FRC materials are very attractive in terms of their physico-chemical properties, concern for possible fire hazard is understandable as organic polymers are one of the major constituents of the materials. A joint study thus was undertaken by the U.S. Army Materials Tech nology Laboratory (MTL) and the Factory Mutual Research Corporation (FMRC) to quantify flammability behavior of selected composite materials for the assessment of fire hazard. In the study, eight FRC materials, identified as MTL #1 to #8, were used. The FRC materials were 3 to 45 mm in thickness. The flammability behavior was examined by using the FMRC Flammability Apparatus (50 kW-Scale) and Ox ygen Index (OI) apparatus, Thermogravimetric Analysis (TGA) instrument, NBS smoke chamber (ASTM E 662), and Gas Chromatograph-Mass Spec trometer (GC-MS) instrument at MTL. This article presents results for ignition, flame spread, heat release rate, gen eration rates of products, light obscuration by smoke and flame extinction by Halon. In comparison to ordinary combustibles, such as cellulosics and most non fire retarded plastics, the eight FRC materials have higher resistance to ig nition (as indicated by the Thermal Response Parameter, TRP) and flame spread (as indicated by higher values of the Fire Propagation Index, FPI). The FPI values for the FRC materials, examined in this study, ranged from 3 to 13, indicating that for Group 1 FRC materials (FPI < 10), self-sustained flame spread beyond the ignition zone would be difficult, whereas for other Group 2 materials ( FPI ≥ 10), flame spread beyond the ignition zone would be ex pected, although at a slower rate. For Group 2 materials fire protection is re quired, which could be provided by techniques such as surface coating, surface lamination using highly fire resistant FRC materials, and others. Generation of heat, smoke, toxic and corrosive products is closely related to FPI. Within the FRC materials, examined in this study, differences were found between the generation rates of heat, smoke, and other products. Results for flame extinction by Halon 1301 are also discussed. The flame ex tinction data are consistent with the design of the current suppression system for the crew compartment of Army combat vehicles. The study suggests that the FPI concept and associated parameters related to generation of heat, smoke, toxic, and corrosive products, is a useful concept for realistic flammability quantification and screening of FRC materials and for use in the hazard assessment. This, however, needs to be validated by perform ing large-scale fire tests.