Bench-scale Fire Tests Research Articles

In situ tensile behavior of hybrid carbon and glass fibers reinforced PEEK laminates: Isothermal or fire testing conditions

This work aims at investigating the thermo-mechanical coupling under critical temperature conditions in hybrid carbon/glass fibers reinforced Poly Ether Ether Ketone (PEEK) laminates. Two testing conditions have been considered: (i) isothermal and (ii) fire condition. A tensile loading was applied in homogeneous and isothermal temperature distribution (Room temperature – 350 and 500 °C) by means of a high-temperature furnace to quantify the influence of temperature on the mechanical response and properties. Regarding the fire conditions, a one-of-a-kind bench-scale fire test combining an in situ tensile mechanical loading and a kerosene burner (a flame temperature of 1100 °C ± 80 °C and a heat flux of 116 kW/m2 ± 10 kW/m2) has been designed and instrumented to induce anisothermal temperature conditions. This prototype allows the evolution of various physical quantities to be tracked as a function of the flame exposure time (5-10-15 min). These include temperature, loss of mass, deformation, stress, which are fundamental for understanding the mechanisms brought into play. The decrease of the tensile properties under isothermal conditions is −38% ± 0.6% (axial stiffness) and −54% ± 0.3% (axial strength) with respect to the values obtained at room temperature. The tensile response under fire is similar to the one obtained in isothermal conditions at 500 °C. The creep behavior of CG/PEEK laminates was also investigated with different boundary conditions (with or without a protective shield reducing the delirious effect of flame in terms of damages within the laminates). Compared to virgin specimens, the residual tensile mechanical properties significantly decrease as a function of the flame exposure time (5-10-15 min): 30% ± 1.1% and −55% ± 1.6% in axial stiffness and strength, respectively.

Bench-scale fuel fire test for materials of rechargeable energy storage system housings

The fire behaviour of electric vehicles (EVs) differs from that of vehicles with combustion engines. Especially the rechargeable energy storage system (REESS) requires special fire protection measures. The fire behaviour of materials for REESS housings plays an important role in the fire resistance of such systems. Full-scale fire resistance tests like gasoline pool fire tests on complete REESS according to the UNECE-R100-8E standard are mandatory for EVs. However, these tests are not applicable for materials used for REESS housings in the material and process development state, due to the high material demand and production costs of the REESS. Standard tests like the limiting oxygen index test, UL94-V test or cone calorimeter test are insufficient to analyse the fire behaviour of thermoplastic and thermoset materials in a gasoline pool fire. This paper describes a bench-scale fuel fire test including several test criteria to evaluate materials for REESS housings on a laboratory scale. This bench-scale fire test is demonstrated on two case studies: fibre-reinforced thermoset plates and thermoplastic sandwich structures.

Bench-scale fire tests of Dark Red Meranti and Spruce finger joints in tension

This study investigates the secondary failure of Malaysian Dark Red Meranti (Shorea spp.) and Spruce (Picea abies) finger joints in a glulam beam in a fire test using a bench-scale test set-up. Secondary failure is the occurrence of failure of the bond lines due to fire and the falling off of the outermost tension layers, exposing the uncharred inner layers to a sudden increase of fire intensity. The lack of published work and the difficulties in describing the behaviour of the finger joints after the secondary failure in a full-scale fire test has identified the need for a simple bench-scale method, incorporating the conditions of the standard fire test. This paper focusses on the performance of the finger joints which together with other defects such as knots and splits are generally the weakest component in the glulam beam. The finger joints were bonded with structural adhesives, specifically phenol resorcinol formaldehyde (PRF) and polyurethane (PUR). They were tested in tension to imitate the failure of finger joints on the tension side of a standard fire test of a glulam beam. Constant heat flux was introduced to the finger-jointed specimens to replicate the secondary failure of a glulam beam in the standard fire test. The results of this study indicate a relationship between the charring rate and density of the specimens, with higher density Dark Red Meranti showing lower charring rate compared to the lower density Spruce specimens. Factors such as constant heat flux as opposed to the time-increasing heat flux exposure and specimen size influenced the charring rate of the specimens. The char rate was measured at the early stages of the fire test, which is known to have higher values since the build-up of the charred layers was not sufficiently substantial to protect the inner unburnt wood. Overall, the bench-scale fire test set-up was able to differentiate the fire performance of the adhesives, with PRF showing better fire performance compared to the specimens finger-jointed with PUR adhesive. In addition, tensile tests at ambient temperature showed no significant difference in tensile strength between finger joints bonded with different adhesives for the same wood species. The tensile strengths of the finger joints bonded with different adhesives were influenced by the temperature profile through the joint. The proposed bench-scale fire test was used to compare the quality of the adhesives in a fire situation, specifically with respect to secondary failure. The PRF was selected as the reference adhesive.

Variation of Intumescent Coatings Revealing Different Modes of Action for Good Protection Performance

Thermal insulation and mechanical resistance play a crucial role for the performance of an intumescent coating. Both properties depend strongly on the morphology and morphological development of the foamed residue. Small amounts (4 wt%) of fiberglass, clay and a copper salt, respectively, are incorporated into an intumescent coating to study their influence on the morphology and performance of the residues. The bench scale fire tests were performed on 75 × 75 × 2 mm3 coated steel plates according to the standard time–temperature curve in the Standard Time Temperature Muffle Furnace+ (STT Mufu+). It provided information about foaming dynamics (expansion rates) and thermal insulation. Adding the copper salt halved the expansion height, whereas the clay and fiberglass change the height of the residue only moderately. The time to reach 500°C was improved by 31% for clay and 15% for the other two fillers. Nondestructive micro computed tomography is used to assess the inner structure of the residues. A transition of the residue from a black, carbonaceous foam with closed cells into an inorganic, residual open cell sponge occurs at high temperatures. This transition is due to a loss of carbon; the change in microstructure is analyzed by scanning electron microscopy. Additional mechanical tests are performed and interpreted with respect to the results of the morphology analysis. Adding clay or copper salt improved the mechanical resistance tested by a factor 4. The additives significantly influence the thickness and foaming dynamics as well as the inner structure of the residues, whereas their influence on insulation performance is moderate. In conclusion, different modes of action are observed to achieve similar insulation performance during the fire test.

Hydrogen cyanide in fire tests

The gas composition of fire smoke depends on the material being burned. Plastics containing nitrogen, e. g. polyurethane, which are used in modern household furnishings release hydrogen cyanide (HCN) under the influence of heat. In order to evaluate the impact of HCN on the ability of victims to react and escape possibilities as well as on the cause of death, the concentration of HCN and other gaseous components of smoke were determined by burning materials containing polyurethane. Bench scale fire tests (smouldering fires) were performed using model sofa samples containing polyurethane. The concentrations of HCN, carbon monoxide (CO) and carbon dioxide (CO2) were measured using Fourier transformation infrared (FTIR) spectroscopy. Additionally, the oxygen (O2) consumption, transmission and optical smoke density were determined. The gaseous concentrations in smoke determined in the bench scale fire tests were compared with the results of an enclosed room fire test (developing fire to full fire). The average maximum concentrations measured were 42 ppm for HCN and 1100 ppm for CO. The measured values can be classified as toxic to humans but are not in the fatal range. In relation to the dominant CO concentration during smouldering fires, the HCN content in fire smoke can only be considered as having a low-grade influence on human poisoning; however, if material containing polyurethane is burned in a full fire the HCN concentration must be considered as at least a contributing factor to the death of fire victims.

Determination of the thermal protective performance of clothing during bench-scale fire test and flame engulfment test: Evidence from a new index

The protective performance of heat- and flame-resistant materials can be studied using a bench-scale test or a full-scale instrumented manikin test. However, there are some limitations of these evaluation methods. The existing bench-scale test could not be applied entirely to assess the thermal protective performance of fabrics if the exposure duration is fixed, while the existing manikin test only provides limited information about the local difference in thermal insulation. This study developed a new index of maximum attenuation factor to second-degree burn injury (maximum attenuation factor) as an improved quantitative method of the thermal protective performance, and then investigated the use of maximum attenuation factor during the bench-scale test as well as the manikin test. It demonstrated that the calculations of maximum attenuation factor were highly repeatable. In both the bench-scale and the manikin test, strong correlations were found between the results derived from the proposed method and the measurements from the existing test method. The results between the bench-scale test and the manikin test can also be compared as a united index.

Enhanced Modelling of Exposed PFP Coatings Based on Bench-scale Fire-tests

Accurate modelling of the behaviour of coatings used as Passive Fire Protections (PFP) is essential for the evaluation of their performance. The changes of the characteristics of PFP materials when exposed to high temperatures can have a significant impact on the safeguard of the protected surface. In this work, laboratory and bench-scale experimental studies of the property changes suffered by a selected PFP coating when exposed to high temperatures were carried out. The results were used in the simulation of a case of study which allowed evaluating the advantages of a detailed model of the coating behaviour. As a conclusion, it was observed that the impact of considering and not considering the property changes of PFP materials when exposed to fire is significant. The results can be used to enhance Finite Element Modelling, leading to a more realistic and better evaluation of the PFP effectiveness.

Generalized pyrolysis model for combustible solids

This paper presents a generalized pyrolysis model that can be used to simulate the gasification of a variety of combustible solids encountered in fires. The model, Gpyro, can be applied to noncharring polymers, charring solids, intumescent coatings, and smolder in porous media. Temperature, species, and pressure distributions inside a thermally stimulated solid are determined by solving conservation equations for the gaseous and condensed phases. Diffusion of species from the ambient into the solid is calculated with a convective–diffusive solver, providing the capability to calculate the flux and composition of volatiles escaping from the solid. To aid in determining the required material properties, Gpyro is coupled to a genetic algorithm that can be used to estimate the model input parameters from bench-scale fire tests or thermogravimetric (TG) analysis. Model calculations are compared to experimental data for the thermo-oxidative decomposition of a noncharring solid (PMMA), thermal pyrolysis of a charring solid (white pine), gasification and swelling of an intumescent coating, and smolder in polyurethane foam. Agreement between model calculations and experimental data is favorable, especially when one considers the complexity of the problems simulated.

Investigation of a combustible material in the fire of Hengyang merchant's building

AbstractAgaric, a kind of important combustible material in the fire of Hengyang merchant's building, was investigated using different experiment equipments. Its degradation and pyrolysis behavior were studied by means of thermogravimetric and kinetic analysis and pyrolysis gas chromatography–mass spectroscopy analysis. External radiation heat and internal heat were used to ignite the agaric. For external radiation ignition, a series of bench‐scale fire tests were done in cone calorimeter in accordance with ISO 5660. As for the internal heat ignition, a fire test was carried out in a full‐scale room in accordance with ISO 9705. Multi‐parameter measurement, including heat release rate (HRR), mass loss rate (MLR), temperature field and species concentration, has been accomplished. Meanwhile, the process of a full‐scale fire test was numerically simulated. The computational results were consistent with experiment data, which will lay down a good foundation for further study in fire reconstruction of the whole fire. Copyright © 2008 John Wiley & Sons, Ltd.

The application of a genetic algorithm to estimate material properties for fire modeling from bench-scale fire test data

A methodology based on an automated optimization technique that uses a genetic algorithm (GA) is developed to estimate the material properties needed for CFD-based fire growth modeling from bench-scale fire test data. The proposed methodology involves simulating a bench-scale fire test with a theoretical model, and using a GA to locate a set of model parameters (material properties) that provide optimal agreement between the model predictions and the experimental data. Specifically, a GA based on the processes of natural selection and mutation is developed and integrated with the NIST FDS v4.0 pyrolysis model for thick solid fuels. The combined GA/pyrolysis model is used with cone calorimeter data for surface temperature and mass loss rate histories to estimate the material properties of two charring materials (redwood and red oak) and one thermoplastic material (polypropylene). This is done by finding the parameter sets that provide near-optimal agreement between the model predictions and experimental data, given the constraints imposed by the underlying physical model and the accuracy with which the boundary and initial conditions can be specified. The methodology is demonstrated here with the FDS pyrolysis model and cone calorimeter data, but it is general and can be used with several existing fire tests and almost any pyrolysis model. Although the proposed methodology is intended for use in CFD-based prediction of large-scale fire development, such calculations are not performed here and are recommended for future work.

Fire calorimetry relying on the use of the fire propagation apparatus. Part I: early learning from use in Europe

The fire propagation apparatus (FPA) is the bench scale fire calorimeter that was recently described in its updated version in ASTM E 2058. The apparatus was originally developed in the USA by Tewarson and co-workers from the mid 1970s, under the name ‘50 kW lab-scale flammability apparatus’, and is therefore still known in Europe as the ‘Tewarson apparatus’. The paper focuses on the experience achieved so far with the first modern version of the apparatus implemented in Europe (France). Part I in this series of articles reports on the main results achieved during the commissioning period of the apparatus. In a first step, preliminary experiments were carried out in order to check and calibrate different sub-equipment of the calorimeter. The results are principally presented for the load cell system and the infrared heating system which are essential pieces of sub-equipment. In a second step, a set of fire tests using methane or acetone as fuel was carried out in order to check and calibrate the overall working of the calorimeter in well-fire conditions. The performance of the calorimeter was also checked when it operates in under-ventilated fires. Relevant testing procedures and potential technical problems are discussed. A set of recommendations are derived from the early learning obtained at the INERIS fire laboratory in order to check the consistency of the results obtained from bench-scale fire tests. These recommendations are thought to be applicable to all types of bench scale fire calorimeters. Copyright © 2005 John Wiley & Sons, Ltd.

Empirical prediction of smoke production in the ISO Room Corner Fire Test by use of ISO Cone Calorimeter Fire Test data

The combustion conditions in the ISO Room Corner Fire Test make it possible to predict full scale smoke production by use of prediction models and bench scale fire test data procured by the ISO Cone Calorimeter Fire Test. The full scale smoke production is governed by the type of material burning only if the rate of heat release is less than 400–600 kW. For higher rates of heat release, the smoke production is more governed by the combustion conditions. The influence of the combustion conditions on the full scale smoke production reduces the possibilities of smoke prediction to materials causing flashover within 10 min in the ISO Room Corner Fire Test. The smoke to heat ratio SQ (m2MJ) was used to compare smoke production between the scales. In general, the comparison revealed that the smoke yield was significantly less in full scale than in bench scale, especially for the plastics. Plastics do yield more smoke than wood based materials in both scales, but the differences in full scale are not as extreme as indicated by the bench scale smoke data. No simple correlations between the scales seem to exist. Multiple regression studies on empirical smoke prediction models show that bench scale fire parameters can be used to predict full scale fire performance. A quite accurate empirical smoke prediction model is presented for the group of materials which caused flashover within 10 min. The model predicts the full scale rate of smoke production at a rate of heat release of 400 kW. The presented results might be used to assess the fire safety hazard of visible smoke, but benchmarks of smoke hazard do not seem to exist. Thus further studies and agreement on safety levels and principles are needed for general visibility analysis concerning fire safety engineering purposes. Copyright © 1999 John Wiley & Sons, Ltd.

Sandwich Panel Performance in Full-scale and Bench-scale Fire Tests

Fire hazard assessments must be primarily driven by life safety variables. Concern is often highly focused on toxicity issues, since fire deaths, in the majority of cases, are found (in whole or in part) to be due to toxic gas inhalation. Procedures have recently been published by ISO, wherein the toxicity assessment of fire products is focused primarily on bench-scale testing for toxic potency (the ‘per-gram toxicity’). Yet hazards of products with regards to fire toxicity may be determined much more by their differences in burning rates than by any differences in toxic potency. Burning rates are not assessed in the pertinent standards (ISO 13344 and ISO TR 9122). For most product categories, techniques for predicting full-scale burning rates from bench-scale data are not yet in hand. Thus, today the best means of comparing actual, full-scale toxic fire hazards is the full-scale fire test, equipped with additional gas measuring instrumentation. Such an approach is not among the recommended methods of the international standards, yet it is the only one with innate validity. In the present work, a series of sandwich panel products were tested in a full-scale room configuration. Bench-scale comparison was made to the ISO 5660 Cone Calorimeter and the DIN 53436 tube furnace. The toxic gases were quantified in all cases by chemical analysis. The product which showed the best performance in the full-scale tests (rock wool insulated sandwich panel) did not achieve a good fire toxicity performance due to minimization of toxic potency. Instead, the successful performance was attributed wholly to reduction of burning rate. Bench-scale measurements of toxic potency were shown to lack relevance to reality in such cases where even the full-scale toxic potency is not a determining factor. © 1997 John Wiley & Sons, Ltd.

Models for calculating flame spread on wall lining materials and the resulting heat release rate in a room

An extensive research programme, dealing with fire growth on combustible wall lining materials, has been ongoing in Sweden over the last decade. Several lining materials were tested in bench-scale fire tests in order to derive basic material flammability parameters. The same materials were also tested in a full scale room test and a 1 3 scale room test for two different scenarios, A and B. Scenario A refers to the case where walls and ceiling are covered by the lining material, Scenario B where lining materials are mounted on walls only. This study utilises the results from these experiments and presents a mathematical model where material properties derived from standardised bench-scale tests are used as input data. The model predicts fire growth in the full- or 1 3 scale tests, in two different scenarios (A and B), and consists of sub-models for calculating the rate of heat release, gas temperatures, radiation to walls, wall surface temperatures and flame spread on the wall lining material. A thermal theory of wind-aided flame spread on thick solids is examined and solutions are given and analysed for flame spread velocities under ceilings. Both numerical and analytical solutions are discussed. The analytical solutions can be used to evaluate the flame spread propensity of materials and thus, whether a certain material is likely to go to flashover or not in the Room Corner Test. More generally, the solutions can be used to estimate whether a material will spread flame in a variety of concurrent flow flame spread scenarios. Results from the analytical solutions are compared with experimental flashover data for 22 materials, showing a good agreement. The numerical solutions are incorporated into a simple room fire model. The results from the numerical model are compared with experiments on 22 materials tested in the full scale room for Scenario A. Comparisons for Scenario B are made with 10 materials tested in the 1 3 scale room. The results show reasonably good agreement for most materials between the model and the experiments.

Effect Of External Radiant Heat Flux On Upward Fire Spread: Measurements On Plywood And Numerical Predictions

In 1992, Factory Mutual Research Corporation (FMRC) and the National Research Council Canada (NRCC) initiated a joint research project on upward flame spread in which NRCC set-up and conducted upward flame spread tests using a large-scale radiant panel facility. The test procedure, developed as part of the joint research project, is described and the results obtained using plywood specimens are discussed. The University of Kentucky team was invited to join this project and to provide their expertise on automated infrared temperature measurements. The identical materials were also tested using a bench-scale fire test apparatus to provide input for the FMRC upward Flame Spread and Growth (FSG) model. An overview of the FSG model and the small-scale tests is provided in this paper. Simulations for both the small-scale and full-scale tests with plywood specimens are provided and comparisons made with the experimental results.

Advances in assessment methods for fire safety

In this paper, the term ‘assessment method’ implies a broad class of standardized experiments which are used in the process of evaluating the fire safety of materials, products or systems. A subset of methods exists which has traditionally been referred to as ‘fire tests’. A brief history of full-scale and bench-scale fire tests is presented. A framework for evaluating the fire performance of building elements, assemblies, contents or materials is described and used to discuss the recent advances in fire tests. The role of fire scenarios is discussed in the context of assessment methods. The continuing theme throughout the paper is the impact of the oxygen depletion method of measuring the rate of heat release, one of the most important advances in the assessment of fire safety during the past 15 years. Corner tests of wall coverings including the effects of changing ‘stand off’ distance between ignition source and the wall of a corner test are discussed. Representative data from a series of different experiments are given to illustrate the use of corner tests. A concept of the critical ignition energy to cause propagation is introduced.

The Rational Development Of Bench-scale Fire Tests For Full-scale Fire Prediction

National standards for flammability have, in most countries, been established for many years. Thus, they are based on an understanding of fire physics which may be several decades old. In more recent times, however, significant strides have been made in developing test methods which are based on an improved understanding of building fires. The best-possible estimate of the flammability of building products or contents would be, by definition, a full-scale fire experiment. These are recently being standardized, and will serve an important reference function. Because of cost and practical difficulties, however, it is generally desirable to do the majority of product evaluations by bench scale tests. In this paper the rational bases for achieving validated bench-scale tests for flammability are examined, and a number of recent examples are cited where such a process has been followed. It is also shown that these test results have a correct relationship to the full scale phenomena.