Dangers relating to fires in carbon‐fibre based composite material

Inhalable carbon fibres have been suspected to pose similar threats to human health as asbestos fibres. It is well‐known that fibres having a diameter of less than 3 µm might be inhaled and transported deep into the human respiratory system. Some composite materials use carbon fibres as structural reinforcement. These fibres do not pose any risks as such as they are firmly connected to the laminate and surrounded by a polymer matrix. Also, these fibres typically have diameters >6 µm and thus, are not inhalable. However, if the material is exposed to a fire, the carbon material might be oxidized and fractionated and thereby, inhalable fibres might be generated into the fire smoke. The capability of carbon fibre‐based composite material to produce dangerous inhalable fibres from different combustion scenarios has been investigated. It was found that the risk of fires generating inhalable carbon fibres is related to the surface temperature, the oxygen level and the airflow field close to the material surface. The temperatures necessary for oxidation of the carbon fibre is so high that it is possible that only a flashover situation will pose any real danger. Other possible danger scenarios are highly intense fires (e.g. a liquid fuel fire), or situations where structural damage is part of the fire scenario. Copyright © 2005 John Wiley & Sons, Ltd.     

Fibre mortar composites in fire conditions

A small-scale test series was carried out using the heating system (radiant exposure) of a cone calorimeter to detect any differences in the way different fibres affect the thermal properties of a standard mortar. The fibres were different polypropylene, polyacrylonitrile, aramide, carbon or steel. Fibres affect the release of moisture from the fibre mortar material. Local pressures caused by water vaporization due to rapid heating can be decreased by incorporating fibres. Fibres have a weak insulating effect. However, use of polyacrylonitrile fibres in mortar may increase the risk to spalling under rapid thermal exposure such as fire. The moisture level in specimens is highly significant for their thermal properties and hence their fire behavior.     

贝壳粉对饰面型防火涂料阻燃性能的影响分析

将贝壳粉与膨胀型防火涂料按一定比例混合,采用隧道燃烧法探测贝壳粉的加入对防火涂料防火阻燃性能的影响。并寻找出最佳配比浓度范围,使废弃贝壳粉能够投入到室内装修材料中形成一种绿色环保的产品。     

New filter materials

The possibility of producing reinforced material for filtration made from basalt fibres and different combinations with glass fibres was demonstrated. The technological production parameters were developed and the physicomechanical indexes of the cloth were determined. It was found that cloth made of basalt fibre had the best air permeability, but the processability was worse than for combined and glass cloth. Cloth with a concentration of 50 wt. % basalt and 50 wt. % glass fibres had the optimum physicomechanical properties and best processability.Berdyansk Glass Fibre Plant. Translated from Khimicheskie Volokna, No. 6, pp. 56–57, November–December, 1994.     

A life‐cycle assessment (LCA) model for cables based on the fire‐LCA model

A novel life‐cycle assessment (LCA) model has been developed for the investigation of the environmental impact of the choice of material in cable production. In the first application polyolefin based material and PVC material is used. In both cases equivalent fire behaviour is assumed and a fire model is established based on existing fire statistics. This study represents the second full application of the fire‐LCA model. In this paper the new ‘cables fire‐LCA’ model will be presented together with the results of this first application. Aspects such as end‐of‐life scenarios, fire statistics, and fire scenarios and large scale fire performance of cables are discussed together with details of the straw LCA model defined for cables and the results of four different end‐of‐life scenarios. Copyright © 2003 John Wiley & Sons, Ltd.     

Mortars containing wood-based fibres under thermal exposure using cone calorimeter heating

The behaviour of concrete structures under fire can be improved by adding fibers. However, relatively little is known of the details of the possible beneficial features of the fibre addition. The aim of this study was to compare the effects of different wood-based fibres on the thermal properties of a standard laboratory cement mortar at conditions of a developing fire. The cone calorimeter heating method was used, and the sample thickness and heat flux were varied (25 mm or 50 mm, 25 kWm^?2 or 50 kWm^?2) to compare test conditions. The fibres comprised chemical pulp, chemi-thermomechanical pulp, recycled fibres and viscose fibres. The fibre content in the mortar was 0.15–0.5% by weight. Temperature and mass loos measurements of oven-dried specimens (moisture content <0.1%) showed no differences between different wood-based fibre mortars and plain mortar. With increasing moisture content (about 5%), however, the presence of fibres affected the release of moisture from the fibre mortar material. With rapid heating of mortars, which have a moisture content of about 5%, local pressures are easily built up. These pressures are mainly caused by free water vaporization. The rear surface temperature measurements indicate that in mortars containing wood-based fibres (0.15–0.5% by weight) the vaporization temperatures may be 20 –25% lower than in the reference mortar. Some effects on heat transfer can also be observed due to differences in water vaporization and movement processes.     

Behaviour of limecrete under fire conditions

Hydraulic lime concrete (limecrete) is a material that has a lower environmental impact than that of ordinary Portland cement (OPC) concrete and, consequently, may be increasingly used in some construction applications. Because of its reduced strength, pozzolanic materials, such as metakaolin, are commonly used to improve its strength and durability. Simultaneously, to the increased interest in more sustainable materials, the fire behaviour of materials has also deserved an increased attention during the last years because of some important disasters that occurred. In this study, the fire behaviour of limecrete has been investigated. To increase limecrete performance, hydraulic lime has been replaced by metakaolin in different percentages. Fire tests at different temperatures (200, 400, 600 and 830°C) and different durations (30 and 60 min) have been performed and the residual strength and chemical changes using X‐ray powder diffraction and thermogravimetric analysis techniques were investigated. It became apparent that a 20% replacement of hydraulic lime by metakaolin leads to an improved performance at room temperature and fire loading. Copyright © 2011 John Wiley & Sons, Ltd.     

Inorganic polymeric materials for passive fire protection of underground constructions

Protection against fire for reinforced concrete constructions is of great importance worldwide. There is a general perception that concrete structures are incombustible and thus, they have good fire‐resistance properties. In a real fire incident, however, concrete can be subjected to excess temperatures causing severe spalling and serious damage to concrete structures with significant economic cost and high potential risk to human life safety. Although a variety of fire‐protection methods exist, there is always a need for the development of new materials with improved thermophysical properties and low cost. Inorganic polymeric materials are promising from this point of view. They are incombustible, combining excellent physical, chemical, mechanical and thermal properties with low production cost and significant environmental benefits. In this work, the thermophysical properties of ferronickel slag‐based inorganic polymeric materials are studied. The results from the laboratory scale experiments are promising and indicative of the large‐scale behavior of material. The effectiveness of this material has to be proved in large‐scale experiments at higher temperatures simulating several severe fire scenarios as well as under all kinds of mechanical loading before concluding for its applicability as a fire protection system. Copyright © 2012 John Wiley & Sons, Ltd.     

Application issue of anthraquinonoid vat dyes on inherently flame-resistant fabrics

The vat dyeing process of specific fabrics with protective, inherently fire retardant properties that have a high content of aramid fibres in their composition, is presented. The research was performed on fabric samples that differ in raw material composition and aramid content. The samples were dyed in raw form (group 1) as well as after pretreatment with alkaline scouring (group 2). Measured limiting oxygen index (LOI) values showed that the selected fabrics meet the properties of inherently fire retardant fabrics. Dyeing was performed with Indanthren® Olive Green HB (manufactured by DyStar) vat dye, in exhaustion process, with a bath ratio of 1:30. The dye concentration was 3%, and sodium-hydrosulphite (Na₂S₂O₄) was used as a reducing agent. The colouristic analyses were performed based on spectrophotometric measurement and results interpretation according to CIELab system. The evaluation of primary tactile properties was performed which show an increase of smoothness and softness after scouring and dyeing. Also, wash fastness as well as light fastness tests have shown satisfactory fastness properties.     

Influence of fibers on bond strength of concrete exposed to elevated temperature

Concrete is a building material having good fire resistance and the resistance depend on many factors including the properties of its constituent materials. Fiber Reinforced Concrete (FRC) apart from improving mechanical properties has better fire resistance than conventional concrete. Bond strength of concrete is one of the important properties to be considered by structural engineers while designing reinforced concrete cements. In this research, an experimental investigation has been carried out to determine the effect of fibers on the bond strength of different grades (M20, M30, M40 and M50) of concrete subjected to elevated temperature. Different types of fibers such as Aramid, Basalt, Carbon, Glass and Polypropylene were used in the concrete with a volume proportion of 0.25% to determine the bond strength by pull-out test. Prior to the pull-out test, the specimens were kept in a furnace and subjected to elevated temperatures following standard fire curve as per ISO 834. Based on the test results of the investigations, type of fiber, grade of concrete and duration of heating were found to be the key parameters that affect the bond strength of concrete. The contribution of carbon fiber in enhancing the bond strength was found to be more significant compared to other fibers. An empirical relationship has been developed to predict the bond strength of FRC at a slip of 0.25?mm. This empirical relationship is validated with experimental results.     

Natural fibre-reinforced biopolymers as construction materials – new discoveries

Originally coming from aerospace technology, fibre reinforced plastics (FRP) are successfully used for various applications because of their excellent specific properties, e. g. high strength and stiffness, low weight and the potential of optimisation by orientating (esp. continuous) fibres along the load paths. In order to successfully meet the environmental problems of these classic composites, the DLR Institute of Structural Mechanics developed an innovative idea in 1989: By embedding natural and near natural reinforcing fibres, e. g. flax, hemp, ramie, cellulose etc., into a biopolymeric matrix from cellulose, starch or lactic acid derivatives, etc. (thermoplastics as well as thermosets), new fibre reinforced materials, called biocomposites, were created and are still being developed. In terms of mechanical properties being comparable to glass fibre reinforced plastics (GFRP), latest developments on new fibre/matrix combinations and environmentally compatible flame retardants enable biocomposites to replace GFRP in most cases. Biocomposites are designed to meet the processing requirements for commonly used manufacturing techniques, e. g. pressing, injection moulding, filament winding, BMC, SMC etc. Apart from anisotropic and specially tailored lightweight structural parts with continuous fibre reinforcements, biocomposites are very well suited for panelling elements in cars, railways and aeroplanes, etc., using different kinds of nonwovens from single fibres (needlefelt nonwovens, fleeces, etc.) to be easily adapted to the usually curved shapes of panellings, fairings, etc.     

Anchorage of carbon nanotubes grown on carbon fibres

A novel reinforcing material based on the concept of an uniform 3-dimensional distribution of carbon nanotubes directly grown on yarns of carbon fibres has been developed. This material shows a potential for applications in polymeric matrix composites, combining the properties of carbon nanotubes with those of a traditional reinforcement.In view of the dipping process of the CNT coated fibres into a polymeric matrix, a good anchorage of CNT to the fibre surface is mandatory. Carbon fibres coated with metallic clusters and CNT were immersed into different liquids (deionised water, ethanol, n-butanol, acetone) and processed with different treatments (immersion, magnetic stirring, centrifugation and ultrasonic bath) in order to test their behaviour in different stressing environments. The morphological features of the samples were characterised by SEM both before and after the tests, demonstrating a good adhesion of the three-component material, which was not destroyed even after the most aggressive test.     

Smoke gas analysis by Fourier transform infrared spectroscopy – summary of the SAFIR project results

The determination of toxic components from fire gases is difficult because the environment is hot, reactions are often temperature dependent, and a lot of soot may be produced. Due to the different properties of the gas components, a different time‐consuming procedure for each species has traditionally been used. The use of FTIR (Fourier transform infrared) spectrometers as a continuous monitoring technique overcomes many of the problems in smoke gas analyses. FTIR offers an opportunity to set up a calibration and prediction method for each gas showing a characteristic spectral band in the infrared region of the spectrum. The objective of the SAFIR project was to further develop the FTIR gas analysis of smoke gases to be an applicable and reliable method for the determination of toxic components in combustion gases related to fire test conditions. The optimum probe design, filter parameters and the most suitable sampling lines in terms of flow rate, diameter, construction material and operating temperature have been specified. In the large scale, special concern was given to the probe design and the effects of the probe location as well as practical considerations of the sampling line length. Quantitative calibration and prediction methods have been constructed for different components present in smoke gases. Recommendations on how to deal with interferents, non‐linearities and outliers have been provided and a verification method for the spectrometer for unexpected variations and for the different models have been described. FTIR measurement procedures in different fire test scenarios have been studied using the recommendations of this project for measurement techniques and analysis and an interlaboratory trial of the FTIR technique in smoke gas analysis was carried out to define the repeatability and reproducibility of the method in connection with a small scale fire test method, the cone calorimeter. Copyright © 2000 John Wiley & Sons Ltd.     

Small-scale assessment method for the fire resistance of historic plaster system and timber structures

The primary protection against the charring of timber is ensured by protection materials. Today, there are only a limited number of materials given in design codes as fire protection materials for timber. Historic surface finish materials such as plasters have rarely been studied with respect to fire; no design values exist in the current fire part of Eurocode 5. Full-scale fire testing is costly to assess the fire performance of material combinations, thus this study presents a useful tool that is specifically tailored to evaluate the fire protection ability of materials in small-scale. A review of conducted tests demonstrate that the cone heater of a cone calorimeter is a dependable device to estimate the charring performance of protected timber specimens as the test results approximate the ones obtained from furnace tests. This work contributes to the assessment of fire resistance performance of various combinations and types of plaster systems found in existing timber buildings that often require an individual approach for an adequate fire risk analysis and design decisions to meet current fire safety regulations with respect to the load-bearing capacity and compartmentation of building structures. Increased knowledge on the fire protection performance of traditional plasters is believed to facilitate their wider use in timber buildings, primarily to preserve their significance as part of the cultural built heritage.     

Degradation mechanisms of SiC/BN/SiC after low temperature humidity exposure

The environmental degradation of SiC/BN/SiC CMCs under low temperature water exposure is still an unexplored field. This work shows how the effect of low temperature humid environments can be detrimental for turbostratic BN interphases, leading to a drop in mechanical properties. Furthermore, initial low-temperature humid environments can induce a faster degradation during subsequent thermal exposure. In order to understand how low temperature water exposure affects the CMC and how these changes affect the material response to subsequent exposures, intermediate temperature (800 °C) exposures have been studied before and after the low temperature humidity tests. The main challenge of this work consists of understanding how different constituents of the CMC structure (e.g. fibres and interphases) are degrading and consequently affecting the overall bulk mechanical performance and failure modes of the material. For this, linking the change in morphology and chemistry of the interphases with the micromechanical properties each constituent has been crucial.     

Roles of graphite oxide, clay and POSS during the combustion of polyamide 6

Two contrasting approaches have been adopted in the current study to obtain environmental benign and superior flame retardant polymer nanocomposites. In the first approach, polyhedral oligomeric silsesquioxane (POSS) is incorporated as an additional filler in polyamide 6/clay nanocomposite to improve the homogeneity of the ‘physical’ barrier, since POSS transforms to a glassy material upon fire and enhances the coupling of silicate layers to each other. In the second approach, fire response of an intumescent system, polyamide 6/graphite oxide (GO), is compared to polyamide 6/clay systems. The intention of using GO as a flame retardant is to benefit from its layered structure (‘physical’ barrier mechanism) and intumescent/blowing effect (‘chemical’ mechanism). Considerable insight and physical knowledge on the roles of different fillers in the combustion process have been obtained, which would provide useful guidance for the development of a new generation of nanocomposites. Besides the obvious contrasting differences in the flame properties of different materials, the incorporation of various fillers, depending on their nature, has both advantages and disadvantages from the viewpoint of flame retardancy.     

Influence of fire retardants on the reaction‐to‐fire properties of coextruded wood–polypropylene composites

The reaction‐to‐fire properties of coextruded wood–plastic composites containing different fire retardants (melamine, zinc borate, ammonium polyphosphate, aluminium trihydroxide, natural flake graphite and expandable graphite) in the shell layer have been studied with the cone calorimetry technique. The effect of ammonium polyphosphate in combination with graphite has also been studied with a cone calorimeter test. A coextruded composite manufactured without any fire retardant addition has been used as a reference. The fire properties measured in the cone calorimeter are discussed, including the heat release rate, total heat release, smoke production, specific extinction area, CO yield and mass loss rate. The results show that the introduction of fire retardants in the shell layer of coextruded wood–polypropylene composites has a favourable effect on the fire resistance properties of the composite materials. The reaction‐to‐fire properties have been improved according to the fire classification of construction products based on the Euroclass system. Copyright © 2015 John Wiley & Sons, Ltd.     

Sodium‐based fire resistant geopolymer for passive fire protection

This paper primarily deals with the examination of the performance under thermal loading of a fire resistant sodium‐based geopolymer from Ferronickel slag. In addition, the mechanical, physical and thermal properties of material and their respective variation with time were measured. It is shown that the material presents good mechanical strength and excellent physical and thermal properties. The behaviour of the material on fire was tested by subjecting it to thermal loading with the modification of a standardized passive fire protection test. Two different fire scenarios were investigated: (1) the least intensive standard ISO 834 fire load curve and (2) the most severe Rijkswaterstaat fire load curve. The material behaviour was excellent under its exposure at the ISO 834 fire load curve, showing optimal thermal insulating function and very good structural integrity. Under the Rijkswaterstaat fire load curve, the material showed again a very good thermal insulating function while at the same time suffered from creeping phenomena at the extremely high temperature of 1300°C that affected drastically its structural integrity. As a conclusion, the sodium‐based geopolymer from FeNi slag may be an appropriate material for passive fire protection systems under cellulosic fires but inappropriate against more intense fire incidents. Copyright © 2014 John Wiley & Sons, Ltd.     

A review on the characterisation of natural fibres and their composites after alkali treatment and water absorption

Natural fibre-reinforced polymer matrix composites are gaining increased attention among the researchers due to their low density, biodegradability, abundance, good mechanical properties, etc. Significant amount of research works can be found on the material characterisation of natural fibres like hemp, flax, sisal, kenaf, coir and jute and their composites based on the polymer matrices. Natural fibres are hydrophilic in nature and exhibit poor interfacial adhesion between fibre and matrix. Modification of the fibre surface by chemical methods, such as alkalisation, benzoylation and acetylation, has been used by researchers to improve the above-mentioned shortcomings. This review paper focuses on the effect of alkali treatment on the material properties of various natural fibres and their composites along with their water absorption behaviour.     

Carbon fibres from mesophase pitch

Union Carbide Corporation has recently developed a process for preparing high-modulus carbon fibres from mesophase pitch. These high-modulus carbon fibres can be prepared from low-cost carbonaceous pitches which have been converted to a liquid crystal state. The liquid crystal or mesophase state results when a proper size distribution of planar aromatic molecules is produced by dehydrogenative condensation reactions. Mesophase pitches can be melt-spun into fibres possessing a high degree of axial preferred orientation which can be preserved and enhanced through carbonizing and graphitizing. Mesophase pitch-derived carbon and graphite fibres can have several transverse structures and are capable of achieving various combinations of high strength and high modulus. Their electronic properties are extremely sensitive to structure and further confirm the graphitizability of carbon fibres derived from mesophase pitch. A number of strength-limiting defects have been identified and their incidence reduced. The number of applications of carbon fibres continues to increase. The unique structure and properties of mesophase pitch-based carbon fibres make them particularly suitable for those applications requiring high stiffness, high electrical conductivity, high thermal conductivity, and low coefficient of thermal expansion.