Speckle Interferometry Analysis of Full-bending Behavior of GFRP Pultruded Material

Abstract

The use of Glass Fiber Reinforced Polymer materials (GFRP) has increased in the last years even among civil structural engineering due to their high specific strength, lightweight and excellent corrosion resistance. With application of the pultrusion method, the manufacture of large-scale profiles with various cross-section forms became potentially possible with relatively low costs. Usually two different technological approaches are available to realize the element: in the first one a mat-roving-mat sequence is adopted, in the second one only roving is present. Continuous filament mat (CFM, fibers distributed randomly in all directions) is often used to build up laminate thickness quickly, as well as to enhance transversal strength and stiffness. Besides, the intrinsic particular features of GFRP materials require the application of new techniques of mechanical analysis to define a correct material model. Many papers study the mechanical behavior of GFRP structural elements at a macroscopic scale even in particular environmental conditions. From the other hand full-field contactless techniques (e.g. digital image correlation, thermal stress analysis, speckle interferometry) are effective tools to correctly model complex mechanical behavior and to define the consequent parameters. Among these techniques, Electronic Speckle-Pattern Interferometry (ESPI) has been asserted as very effective due to the technological improvements of the laser sources. One of the significant advantages of ESPI is to produce real-time fringe patterns on objects with optically rough surfaces, with a displacement sensitivity of the order of the light wavelength. Aim of the paper is to apply ESPI handled by phase-stepping technique to the experimental study of GFRP materials in the case of mat-roving-mat sequence.