Abstract
Lightweight structures which consist to a large extent of carbon fiber reinforced plastics (CFRP), often lack sufficient damping behavior. This also applies to hybrid laminates such as fiber metal laminates made of CFRP and aluminum. Since they are usually prone to vibrations due to their high stiffness and low mass, additional damping material is required to meet noise, vibration and harshness comfort demands in automotive or aviation industry. In the present study, hybrid carbon fiber elastomer metal laminates (HyCEML) are investigated which are intended to influence the damping behavior of the laminates by an elastomer interlayer between the CFRP ply and the aluminum sheets. The damping behavior is based on the principle of constrained layer damping. To characterize the damping behavior, dynamic mechanical analyses (DMA) are performed under tension on the elastomer and the CFRP, and under three point bending on the hybrid laminate. Different laminate lay-ups, with and without elastomer, and two different elastomer types are examined. The temperature and frequency dependent damping behavior is related to the bending stiffness and master curves are generated by using the time temperature superposition to analyze the damping behavior at higher frequencies. A numerical model is built up on the basis of DMA experiments on the constituents and micro mechanical studies. Subsequently, three point bending DMA experiments on hybrids are simulated and the results are compared with the experimental investigations. In addition, a parameter study on different lay-ups is done numerically. Increasing vibration damping is correlated to increasing elastomer content and decreasing elastomer modulus in the laminate. A rule of mixture is used to estimate the laminate loss factor for varying elastomer content.
Highlights
Fibre metal laminates (FML) like glass reinforced aluminum (GLARE) or aramid reinforced aluminum (ARALL) are known for many decades for their good specific elastic, impact and fatigue properties [1,2,3]
The difficulties result from different electronegativities which can lead to delaminations due to corrosion, as well as different thermal expansion coefficients which lead to residual stresses in the material, especially with carbon fibers due to their low thermal expansion coefficient and high modulus [1,3]
dynamic mechanical analyses (DMA) on the neat elastomer and carbon fiber reinforced plastics (CFRP) were done in uniaxial tension mode, whereas the fiber metal elastomer laminates (FMEL) and FML were analyzed by three point bending (3PB)
Summary
Fibre metal laminates (FML) like glass reinforced aluminum (GLARE) or aramid reinforced aluminum (ARALL) are known for many decades for their good specific elastic, impact and fatigue properties [1,2,3]. Besides the integration of an glass fiber reinforced (GFRP) interlayer between the CFRP and aluminum sheet [5,6], elastomeric interlayers have proven to solve these interfacial problems [7,8,9] These laminates are called fiber metal elastomer laminates (FMEL). When substituting the glass fibers by carbon fibers in an FML a much stiffer behavior was obtained, the loss factors were even smaller than on the neat aluminum and CFRP [16] It is, assumed that in comparison to FMEL with GFRP, the additional elastomer layers increase the damping of FMEL, which contain generally very low-damping CFRP layers. The elastomer layer will partially influence the bending stiffness
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