The use of glass fiber reinforced polymer materials (GFRP) has increased in recent years for structural engineering. The intrinsic non isotropic nature of GFRP materials together with many manufacturing characteristics encourages the extensive investigation of the real constitutive behaviour. Among the full-field contactless techniques electronic speckle-pattern interferometry (ESPI) plays an important role as a result of its capability to produce real-time fringe patterns on objects with optically rough surfaces, with a displacement sensitivity close to the light wavelength. The aim of this paper is to experimentally analyze the bending behaviour of GFRP specimens. This goal is achieved first by applying ESPI, handled by a phase-stepping technique, to obtain the experimental four-point flexural response of GFRP prismatic specimens with their longitudinal axis aligned with the pultrusion direction as well as with the orthogonal one. All the analysis are carried out by means of an in-plane set-up configuration and the images obtained are filtered by an appropriate developed iterative filter. The second step is to numerically reproduce the experimental behaviour by suitably setting the constitutive material model in an appropriate finite element code. The results obtained confirm that the GFRP material tested does not behave in an isotropic way and possesses a different Young's modulus in tension and compression. © Civil-Comp Press, 2014.

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