Abstract
Within this contribution, the low-velocity impact behavior of sandwich structures was investigated. The sandwich structures consisted of carbon fiber reinforced polymer (CFRP) face sheets in various setups, and different core structures, including an open-cell and a closed-cell aluminum foam. The matrix of the face sheets was foamed polyurethane, which also acts as the adhesive connecting the face sheets to the core. Low-velocity indentation tests were carried out with multiple sandwich configurations. The indentation behavior was further examined by additional quasi-static indentation tests, and in situ indentation tests sequentially recorded by X-ray computed tomography. Both the low velocity indentation tests and the quasi-static tests were supported by digital image correlation measurements of the lower specimen surfaces. The overall indentation behavior was described consistently to sandwich structures with different material combinations in literature. The influence of each sandwich configuration parameter on the indentation behavior was determined and described in detail.
Highlights
Apart from quasi-static bending stiffness [1,2,3], the rigidity to dynamic impact loads at low to medium velocity is a critical characteristic for sandwich structures, while maintaining a low weight
They compare different impact velocities, including quasi-static indentation tests [7,8], and observe the absence of any velocity-induced influence, since the force-indentation graphs show good resemblance. They use low impact velocities for partial perforation of the specimens at various stages, in order to connect the failure behavior of the specimens to characteristic parts of the force-indentation graphs. They investigate sandwich structures with aluminum face sheets laminated with glass fiber reinforced plastics (GFRP) [9,10,11], which fail significantly less ductilely than the tested sandwich structures with pure aluminum face sheets, and show delamination between the GFRP and the aluminum layers
Low velocity impact testing (LVI) tests were conducted on a variety of sandwich configurations, accompanied and compared to quasi-static indentation tests, which were supported by Digital image correlation (DIC) and computed tomography (CT) measurements
Summary
Apart from quasi-static bending stiffness [1,2,3], the rigidity to dynamic impact loads at low to medium velocity is a critical characteristic for sandwich structures, while maintaining a low weight. Crupi et al [7,8,9] present substantial work on LVI properties of sandwich structures with aluminum face sheets and closed-cell aluminum foam cores They compare different impact velocities, including quasi-static indentation tests [7,8], and observe the absence of any velocity-induced influence, since the force-indentation graphs show good resemblance. They use low impact velocities for partial perforation of the specimens at various stages, in order to connect the failure behavior of the specimens (and their components) to characteristic parts of the force-indentation graphs. They investigate sandwich structures with aluminum face sheets laminated with glass fiber reinforced plastics (GFRP) [9,10,11], which fail significantly less ductilely than the tested sandwich structures with pure aluminum face sheets, and show delamination between the GFRP and the aluminum layers
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