Temperature Dependency of the Deformation Behavior of Hybrid CFRP/Elastomer/Metal Laminates under 3-Point Bending Loads

Abstract

Fibre-metal-elastomer laminates offer the possibility of using material combinations which often have to deal with premature delamination, for example due to different coefficients of thermal expansion or galvanic corrosion due to different electronegativities. The present study deals with laminates made of layers of CFRP and aluminum, each of which is bonded together by an elastomer layer. The shear-soft elastomer also allows the much stiffer aluminum and CFRP layers to be sheared off against each other under bending stress. This leads to complex deformation behavior. The shear of the elastomer also plays a crucial role in the damping behavior of the laminate. Due to large shear deformations in the elastomer layer, the combination of rigid layers and soft elastomer layers shows very good damping behavior according to the principle of constrained layer damping. Since bending vibrations that occur during normal use usually have only small amplitudes, the deformation behavior is of particular interest in the elastic range. Since this deformation behavior is strongly dependent on the shear modulus of the elastomer used and this in turn is strongly influenced by temperature, the deformation behavior is characterized at different temperatures. Within the scope of this investigation, quasi-static 3-point bending tests are carried out on different laminate lay-ups in the temperature range from -40 °C to +80 °C. The laminates are consolidated by compression molding and contain two different EPDM elastomers in varying layer thicknesses, unidirectional CFRP prepreg in biaxial layer lay-up and aluminum 2024 sheets. The deformation behavior is analyzed by digital image correlation. This is used to measure both the bending line of the overall composite and strains over the layer thickness. In particular, the shear in the elastomer layers is evaluated and set in relation to the bending lines. Finally, the ability of the laminate lay-up to damp bending vibrations is evaluated.