Thermo Mechanical Analysis of Composite Material Exposed to Fire

Composites Part B: Engineering, 2004

Simple-to-use models are presented in this paper for determining the residual tension, compression and flexural properties of burnt fibre reinforced polymer composite materials following a fire. The post-fire mechanical properties are calculated using analytical equations that combine the properties of the fire-damaged (i.e. char) and undamaged regions of a composite. Fire tests were performed on composites containing carbon, glass or Kevlar fibres with an epoxy, polyester, vinyl ester or phenolic resin matrix to assess the accuracy of the models. The composites were tested to a wide range of fire conditions with temperatures from 525 to 850 8C for times up to 30 min. It is found that the post-fire properties drop rapidly with increasing heat flux and duration of a fire due to the thermal degradation of the polymer matrix. It is shown that the reduction to the post-fire properties of the burnt composites can be accurately determined using the models. In almost all test cases, the agreement between the calculated and measured residual mechanical properties is within 10%.

Journal of Composites Science, 2019

The main objective of the present study was to develop a fire thermal model able to predict the evolution of the temperature and decomposition gradient across a laminated composite structure when exposed to fire. The thermal response of composite laminate made of organic polymer matrix was investigated under severe temperature conditions as samples were exposed to high temperatures up to 750 °C. The highlight is that a behavior law for water is included in our thermo-mechanical model to estimate effects due to a moisture content field on the thermal response of composite laminates. In particular, porosity and gas pressure are strongly influenced by the presence of water in the material and modify the thermal behavior accordingly. This enabled us to propose a new approach that can be used for the prediction of hygro-thermo-chemico-mechanical post-combustion properties in a very large number of material and fire scenarios.

The present contribution details the development and implementation of dedicated material models for the finite element computation of the thermal and mechanical response of polymer composite structures subjected to fire. The material models are developed so that mechanical and thermal properties at the ply level can be calculated from the constituent's properties, therefore allowing for a greater flexibility in architecture and reduced testing programs. The degradation of the resin during fire is predicted during the thermal analysis. Its effect, together with the effect of temperature, on the mechanical response is accounted for in the material model. The models are validated against a mini furnace experiment.

Plastics, Rubber and Composites, 2003

A thermomechanical modelling approach is proposed for estimating the residual properties of fibre reinforced polymer composites damaged by fire. The modelling was carried out in two parts: (i) prediction of the extent of thermal decomposition (or charring) using a thermal model; and (ii) prediction of the post-fire behaviour using a two layer model that combines the properties of the undamaged laminate and the residual char. Fire experiments were performed on glass-polyester, vinyl ester, and phenolic laminates using a cone calorimeter operated at heat fluxes in the range 25-100 kW m−2, for times up to 30 min. After cooling to room temperature the thickness of the thermal damage layer was determined, along with values of the residual tensile, compressive and flexural properties. For the 'two layer' model it was found that the effective boundary between char material and undamaged laminate corresponded to the point where the residual resin content (RRC) of the laminate was 80%. Surprisingly, this value was found to hold for all three resin types tested. Using this RRC value, excellent agreement was found between the measured and predicted post-fire char thickness and the residual mechanical properties. The approach presented is the first reliable method for accurately predicting the residual properties of composites after fire.

Journal of Composite Materials, 2004

This paper reports on changes to the mechanical properties of woven glass laminates with polyester, vinyl ester and phenolic resins during fire exposure. Two sets of experiments were carried out. First, unstressed laminates were exposed to a constant one-sided heat flux (50 kW m 2) for various times, and the residual post-fire strength at room temperature was reported. In a second series of experiments, laminates were tested under load. The times corresponding to a given loss of properties were 2-3 times shorter than in the previous case. It was found in both cases that modes of loading involving compressive stress were more adversely affected by fire exposure than those involving tension. A simple ‘two-layer’ model is proposed, in which the laminate is assumed to comprise (i) an unaffected layer with virgin properties and (ii) a heat-affected layer with zero properties. For residual properties after fire, the ‘effective’ thickness of undamaged laminate was calculated using this mod...

Processes

In this study, the hygro–thermo–mechanical responses of balsa core sandwich structured composite was investigated by using experimental, analytical and numerical results. These investigations were performed on two types of specimen conditions: dry and moisture saturation sandwich composite specimens that are composed of E-glass/polyester skins bonded to a balsa core. The wet specimens were immersed in distilled water at 40 °C until saturated with water. The both dry and wet sandwich composite specimens were heated by fire. The mass loss kinetic and the mechanical properties were investigated by using a cone calorimeter following the ISO 5660 standard and three-point bending mechanical test device. Experimental data show that the permeability and fire resistance of the sandwich structure are controlled by two composite skins. Obtained results allow us to understand the Hygro–Thermo–Mechanical Responses of the sandwich structured composite under application conditions.

This keynote paper presents a critical review of research progress in modelling the damage and failure of polymer matrix composites exposed to fire. Models for analysing the thermal, chemical and physical processes that control the structural response and failure of composite materials in fire are briefly reviewed.

Proceedings of the 11th …, 2010

The paper presents a numerical model implemented in the Abaqus finite element code for fire resistance of timber members. The fire resistance is evaluated in a two-step process: first, a thermal analysis of the member exposed to fire is carried out, and then a structural analysis under a constant load is performed over time. In the structural analysis, the reduction in mechanical properties (modulus of elasticity and strength) of timber with temperature is considered. The analysis terminates when the member cannot longer redistribute stresses from the hottest to the coldest parts, leading to structural failure. The model was used to simulate fire tests carried out on specimens loaded in tension made from laminated veneer lumber (LVL). Experimental data in terms of temperature, displacement and failure time were compared with numerical results carried out assuming the thermal properties and degradation of mechanical properties with temperature suggested by the Eurocode 5, showing acceptable approximation.

The relationship between heat release rate and other fire reaction properties of fibre reinforced polymer composite materials is investigated. The heat release rate and fire reaction properties of thermoset matrix composites reinforced with combustible fibres (aramid, extended-chain polyethylene) or non-combustible fibres (glass, carbon) were determined over a range of heat flux levels using the oxygen consumption cone calorimeter technique. The fire reaction properties that were measured were time-to-ignition, smoke density, carbon monoxide yield, carbon dioxide yield, mass loss rate and total mass loss. It is discovered that these reaction properties (apart from ignition time) are linearly related to the heat release rate for composites containing non-combustible fibres. When the reinforcement is combustible, however, the heat release rate only appears to be related to the carbon monoxide yield, mass loss rate and (in some cases) smoke density. This study clearly shows the importance of the relationship between heat release rate with smoke density and carbon monoxide yield, the two reaction properties that influence the survival of humans in fire. q

Solid Mechanics and Its Applications