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Low-velocity Impact Response and Compression After Impact Behavior of Non-planar Composites Sandwich Structures

Carbon fiber reinforced plastic (CFRP) sandwich facesheets with lightweight core material (such Nomex®) can provide high stiffness-to-weight ratio and strength. This advantage makes the composite sandwich a popular material choice in transport, marine, and aerospace applications. In this study, we examine the mechanical response of CFRP facesheets with Nomex® honeycomb core composite sandwich tubes with a specific focus on transverse low-velocity impact (LVI) and axial compression after impact (CAI) tests. First, specimens with and without core material are subjected to impact energy level of 25 J, using two different shape impactors: hemispherical and cylindrical. The impact behavior observed by impact force, displacement profile and absorbed energy show that honeycomb core composite sandwich tubes exhibit higher resistance and tolerance to impact damage. Subsequently, quasi-static loading in axial direction is performed to determine CAI failure modes and residual strength of the specimens. The failure mechanisms during LVI and CAI are also observed by X-ray micro-computed tomography (μCT) technique, namely matrix crack, delamination and fiber breakage/splitting in facesheets as well as honeycomb crashing and buckling in the core. The phenomenon of these failure modes agrees with the structural strength obtained from mechanical tests. These results demonstrate the response of non-planar sandwich composites structure under compression test for impacted composite specimens, which could be useful for practical designs and applications.