Connection development and in-plane response of glass fiber reinforced polymer sandwich panels with reinforced cores

This paper presents the findings of an experimental research project that was conducted in two phases to study the behavior of glass fiber reinforced polymer (GFRP) sandwich panels with reinforced cores under in-plane loading conditions. The tested panels consisted of two GFRP face skins separated by a polymeric foam core. The foam core was reinforced with different configurations of through-thickness fiber insertions and through-thickness GFRP web skins. In the first phase the performance of three different types of structural connections was tested--namely, bolted, bonded, and so-called enhanced bolted connections. The findings indicate that bolted connections to thinner and more flexible panels exhibited lower strength and a higher degree of nonlinear behavior compared with the bonded connections to the same panels. In contrast, the bolted connections to thicker and stiffer panels were generally stronger and stiffer than their bonded counterparts. The findings further indicate that the ultimate strength of the connections can be increased by up to 26% by bonding a steel reinforcing plate to the face skins of the panel prior to bolting. In the second phase three full-scale sandwich panels (1400 mm x 1400 mm) with different panel configurations were tested under proportional, biaxial, in-plane loading. The applied loads were selected to simulate the in-plane loading conditions in sandwich panels that are subjected primarily to in-plane loads, such as webs of deep beams and shear walls in lightweight structures. The full-field strains and displacements of the panels were measured using a digital image correlationbased (DIC) non-contact measurement system. The findings indicate that the through-thickness core reinforcements effectively prevented localized buckling, debonding, and separation of the panels' face skins. The findings also demonstrated that slender panels exhibit shear-compression buckling failures, whereas less slender panels exhibit shear-tension rupture failures. Key words: digital imaging techniques, fastening, fiber reinforced polymer sandwich panels, shear. Cet article presente les conclusions d'un projet de recherche experimental, realise en deux phases, visant a etudier le comportement des panneaux-sandwich en polymeres renforces de fibre de verre (PRFV) munis de noyaux armes sous des conditions de chargement en plan. Les panneaux a l'essai comportaient deux revetements en PRFV separes par un noyau de mousse de polymere. Ce noyau de mousse etait arme en utilisant differentes configurations d'intersections de fibres sur toute l'epaisseur ainsi que des revetements de l'ame en PRFV sur toute l'epaisseur. Durant la premiere phase, le rendement de trois types de raccords structuraux ont ete mis a l'epreuve : boulonnes, lies et les raccords boulonnes communement appeles ameliores. Les resultats indiquent que les raccords boulonnes sur des panneaux plus minces et plus flexibles montraient une plus faible resistance et un niveau plus eleve de comportement non lineaire que les raccords lies sur les memes panneaux. A l'oppose, les raccords boulonnes sur des panneaux plus epais et plus rigides etaient generalement plus resistants et plus rigides que les raccords lies. Les resultats indiquent aussi que la resistance a la rupture des raccords peut etre augmentee jusqu'a 26 % en liant une plaque d'armature en acier aux revetements du panneau avant le boulonnage. Durant la deuxieme phase, trois panneauxsandwich a pleine echelle (1400 mm x 1400 mm) de differentes configurations de panneaux ont ete mis a l'epreuve sous chargement proportionnel, biaxial et en plan. Les charges appliquees ont ete choisies pour simuler les conditions de chargement en plan dans les panneaux-sandwich soumis principalement a des charges en plan, tels que les ames des poutres cloisons et les murs de contreventement dans les structures legeres. Le plein champ des contraintes et des deplacements des panneaux ont ete mesures en utilisant un systeme de mesure sans contact de correlation d'image numerique. Les resultats indiquent que les renforcements de noyau a pleine epaisseur previennent efficacement le flambement, le decollage et la separation localises des revetements des panneaux. Les resultats demontrent egalement que les panneaux plus elances presentent des defaillances par flambement en cisaillement/compression alors que les panneaux moins elances comportent des defaillances par rupture en cisaillement/traction. [Traduit par la Redaction] Mots-cles: techniques d'imagerie numerique, fixation, panneaux-sandwichs en polymere renforce de fibres, cisaillement.
Introduction Sandwich structures typically consist of two thin, strong, and stiff face skins that are separated by a thicker, weaker, and more flexible core. The skins may be fabricated from [...]