Creep behaviour of sandwich panels with rigid polyurethane foam core and glass-fibre reinforced polymer faces: Experimental tests and analytical modelling

Abstract

This paper presents experimental and analytical investigations about the creep behaviour of sandwich panels comprising glass-fibre reinforced polymer faces and rigid polyurethane foam core for civil engineering applications. A full-scale sandwich panel was tested in bending for a period of 3600 h, in a simply supported configuration, subjected to a uniformly distributed load corresponding to 20% of the panel's flexural strength. Additionally, specimens of polyurethane foam core were tested in shear for a period of 1200 h, for three different load levels corresponding to 10%, 20% and 30% of the foam's shear strength. Experimental results were fitted using Findley's power law formulation. Creep coefficients, shear modulus reduction factors and time-dependent shear moduli were obtained for the polyurethane foam in shear. A composed creep model is proposed to simulate the sandwich panel's long-term creep deformations by considering the individual viscoelastic contributions from (1) the core material in shear and (2) the glass-fibre reinforced polymer faces in tension/compression. The composed creep model predictions adequately reproduced the full-scale panel's experimental results. In addition, a good agreement was found between the composed creep model predictions and the extrapolation of the power law fitting obtained from the full-scale panel test, for a 50-year period.

A review on recent advances in sandwich structures based on polyurethane foam cores

“…Researchers in past years have used different numerical and experimental techniques to study the creep performance of PUF core sandwich panels. Garrido et al used analytical modeling and performed experimental tests to study the creep behavior of sandwich composite panels with GFRP face sheets and RPUF cores. A full‐scale sandwich panel was manufactured and tested for creep under simply supported conditions of bending for 3600 hours.…”

Pre-design guidelines for GFRP composite sandwich panels

“…Recent work (Keller, 2008;Keller, Vallée, & Murcia, 2008;Sharaf & A., 2008) including studies at IST (M. A. Garrido, Correia, Branco, & Keller, 2014; demonstrated the structural efficiency by enhancing polyurethane cores with lateral ribs (webs) in GFRP. Having regard to its lightness, this material is economically competitive for the construction of temporary structures in disaster/ emergency situations and in the rehabilitation of old structures.…”

“…In this work, the composite creep modelling (CCM) approach, which entails an equivalent stiffness methodology that has been proposed in (Garrido et al, 2014) for simple panels and in (Mário Garrido et al, 2016) for panels with ribs, was adopted for the calculation of the long term displacements due to creep. The CCM approach considers creep in sandwich panels as a result of creep of its individual materials/components.…”

Creep calculation for a three-layer beam with a lightweight filler

“…An experimental study of the creep of foam filler and three-layer beams is carried out in [12][13].However, the authors use Findley's power law, in which the time is contained in an explicit form. Such a law cannot be used for complex loading regimes.…”