Tensile Strength Modeling of Glass Fiber–Polymer Composites in Fire

¹ School of Aerospace, Mechanical & Manufacturing Engineering, Royal Melbourne Institute of Technology, GPO Box 2476V, Melbourne, Victoria, 3001, Australia and Cooperative Research Centre for Advanced Composite Structures Ltd (CRC-ACS) 506 Lorimer Street, Fishermans Bend, Victoria, 3207, Australia
² Centre for Composite Materials Engineering, Stephenson Building, University of Newcastle-upon-Tyne, UK
³ Platform Sciences Laboratory, Defence Science & Technology Organisation, GPO Box 4331, Melbourne, Victoria, 3001, Australia

^* To whom correspondence should be addressed.

	Abstract

A thermal-mechanical model is presented to calculate the tensile strength and time-to-failure of glass fiber reinforced polymer composites in fire. The model considers the main thermal processes and softening (mechanical) processes of fiberglass composites in fire that ensure an accurate calculation of tensile strength and failure time. The thermal component of the model considers the effects of heat conduction, matrix decomposition and volatile out-gassing on the temperature–time response of composites. The mechanical component of the model considers the tensile softening of the polymer matrix and glass fibers in fire, with softening of the fibers analyzed as a function of temperature and heating time. The model can calculate the tensile strength of a hot, decomposing composite exposed to fire up to the onset of flaming combustion. The thermal-mechanical model is confined to hot, smoldering fiberglass composites prior to ignition. Experimental fire tests are performed on dry fiberglass fabric and fiberglass/vinyl ester composite specimens to validate the model. It is shown that the model gives an approximate estimate of the tensile strength and time-to-failure of the materials when exposed to one-sided heating at a constant heat flux. It is envisaged the model can be used to calculate the tensile softening and time-to-failure of glass–polymer composite structures exposed to fire.

Key Words: polymer–matrix composites (PMCs), thermomechanical properties, modeling, glass fibers, fire.

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