Mechanical behaviour of pultruded glass fibre reinforced polymer composites at elevated temperature: Experiments and model assessment João R. Correia ⇑ , Marco M. Gomes, José M. Pires, Fernando A. Branco Department of Civil Engineering and Architecture, Instituto Superior Técnico/ICIST, Technical University of Lisbon, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal article info Article history: Available online 24 November 2012 Keywords: GFRP profiles Pultrusion Elevated temperature Mechanical behaviour Experimental tests Degradation models abstract This paper presents an experimental and analytical study about the mechanical response at elevated tem- perature of glass fibre reinforced polymer (GFRP) pultruded profiles. The paper first describes results of DMA and DSC tests that were used to evaluate the glass transition and decomposition processes of the GFRP pultruded material. The paper then describes an extensive study about the tensile, shear and com- pressive responses of the GFRP material at temperatures varying from 20 °C to 250 °C. In these tests the mechanical responses of the GFRP material as a function of temperature were assessed, namely the load– deflection curves, the stiffness, the failure modes and the ultimate strength. Results obtained in these experiments confirmed that the mechanical performance of GFRP is severely deteriorated at moderately high temperatures, particularly when loaded in shear and compression, owing to the glass transition of the resin. The final part of this paper assesses the accuracy of different empirical models and one phe- nomenological model to estimate the tensile, shear and compressive strengths of GFRP pultruded mate- rial as a function of temperature. All empirical models, including a function based on Gompertz statistical distribution suggested in the present paper, provided accurate estimates of tensile, shear and compres- sive strengths as a function of temperature. The phenomenological model was less accurate and in gen- eral provided non conservative estimates of material strength. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction The use of fibre reinforced polymer (FRP) composites has grown at an extraordinary rate since the 1960s, owing to their main advantages over traditional materials – these include high strength, lightness and corrosion resistance. These materials now have a wide range of applications in aircraft, spacecraft, ships, automobiles, sporting goods and civil infrastructure. While FRP materials are being increasingly used in civil engineer- ing applications [1,2], new design issues and challenges are inevita- bly encountered. Among these issues, there are legitimate concerns regarding the performance of FRP materials when exposed to fire, especially in building applications. This is basically due to the fact that the strength, stiffness and bond properties of FRPs are severely deteriorated at moderately elevated temperatures, namely when the glass transition temperature (T g ) of the resin is approached, typ- ically in the range of 60–140 °C. Furthermore, when exposed to tem- peratures of about 300–500 °C, the organic matrix of FRPs decomposes, releasing heat, smoke, soot and toxic volatiles [3,4]. In spite of the above mentioned concerns, fire resistance tests on glass fibre reinforced polymer (GFRP) pultruded tubular beams, recently carried out at Instituto Superior Técnico (IST) [5,6], showed that it is possible to fulfil stringent building code fire requirements. In those tests, different passive and active fire pro- tection systems were successfully used and provided fire resis- tances longer than 60 min and 120 min, respectively. In addition, it was observed that GFRP profiles are much more vulnerable un- der compression and shear than under tension – in all tests, although the bottom flange of the profiles was submitted to tem- peratures well above the decomposition temperature (T d ) for long periods of time, tensile failure never occurred. Conversely, failure always occurred due to compressive and/or shear stresses, where temperatures were much lower, i.e. either at the top flange in the vicinity of midspan or at the upper part of the webs under the applied load sections. Other earlier studies [7] have also shown that it is possible to extend the fire endurance of GFRP structural members if appropri- ate fire protection systems are used. However, in order to enable the structural use of GFRP profiles in building applications, fire de- sign methods are still to be developed. One step towards such development involves the careful description of GFRP material mechanical behaviour at elevated temperature – as for other mate- rials, duly validated design curves expressing the degradation of mechanical performance as a function of temperature are needed. In order to develop such degradation curves, a wealth of experi- mental data is needed. However, presently only a limited number of studies are available in the literature. 0263-8223/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.compstruct.2012.10.051 ⇑ Corresponding author. Tel.: +351 218 418 212; fax: +351 218 488 481. E-mail address: jcorreia@civil.ist.utl.pt (J.R. Correia). Composite Structures 98 (2013) 303–313 Contents lists available at SciVerse ScienceDirect Composite Structures journal homepage: www.elsevier.com/locate/compstruct