Numerical and experimental investigations on sandwich panels made with eco-friendly components under low-velocity impact

Abstract

A low-velocity impact characterisation of a sustainable sandwich panel based on upcycled bottle caps as circular honeycomb is conducted. The recycled core aims to develop an alternative route of reusing waste bottle caps disposed in landfills. Ecological alternatives to skin (recycled PET foil) and adhesive (bio-polyurethane) are also compared with classic components (aluminium skin and epoxy polymer). A low-cost reinforcement (cement particles) is also proposed to enhance the mechanical strength of the panel. The samples are tested at several levels of impact energy, according to the type of skin, to observe their effect on mechanical behaviour. Metal skins achieve higher impact loads and energy absorption compared to PET foil. The bio-adhesive leads to a similar or enhanced maximum impact load and energy absorption compared to the epoxy adhesive. Specific properties highlight the promising performance of the bio-based adhesive with aluminium skins, reaching increments of up to 378%. The cement increases the maximum load and reduces the duration of the impact event, leading to lower energy absorption. The unreinforced epoxy polymer shows a visible adhesive peeling off from aluminium skin, while particle inclusions lead to reduced overall delamination. Biopolymer exhibits marginal adhesive debonding and stable deformation, revealing a progressive failure. In general, PET samples show core shear failure due to rupture of the skin. Crack propagation in PET samples made with biopolymer adhesive is reduced at lower energy levels. The results evidence the promising application of bottle caps in a more sustainable honeycomb core to build eco-friendly structures.

Environmental assessment of discarded plastic caps as a honeycomb core: An eco‐mechanical perspective

“…The variations of sandwich panel inventory affect not only the environmental impact, as indicated in the sensitivity analysis, but also the mechanical performance of the resulting designs. This aspect was verified in previous studies (Oliveira et al, 2020;Oliveira et al, 2021a;Oliveira et al, 2021b), which compared the mechanical properties of bottle cap panel designs with different skins (aluminum, PET foil, and flax laminate) and adhesives (epoxy and biopolymer), also reducing the skin and the adhesive amount by 50 and 33/67%, respectively. However, the environmental potential of these modified designs has not been determined.…”

“…The product investigated in this study is the sandwich panel made with a core based on HDPE bottle caps of Coca‐Cola™ beverages commercialized in Brazil (Oliveira et al., 2020; Oliveira et al., 2021a; Oliveira et al., 2021b). The aim of the present LCA is to determine the environmental impacts of producing the eco‐friendly sandwich panel based on bottle caps honeycomb core by studying the effect of different panel compositions (e.g., various skins and adhesives).…”

“…Specific flexural strength versus GWP plots with eco‐mechanical indicator lines (GWP σ ) for the designs tested experimentally by Oliveira et al. (2020; 2021a; 2021b), Le Duigou et al. (2012), and Segovia et al.…”

“…The LCI analysis is based on the inventory defined by the authors of the current study for the manufacture the proposed bottle cap panels (Oliveira et al., 2020; Oliveira et al., 2021a; Oliveira et al., 2021b). The thickness of the flax skins is adjusted from reference works to comply with the flexural rigidity determined in FU 1 (see Table S2 of the Supporting Information).…”

“…Bottle caps as sandwich panel core showed promising flexural resistance when combined with classic components, such as aluminum and epoxy (Figure 1a) (Oliveira et al., 2017; Oliveira et al., 2018). Recently, eco‐friendly designs based on recycled and renewable skins and bio‐based polyurethane (bio‐PU) as an adhesive (Figure 1b,c) have been tested to reduce environmental damage and obtain good mechanical properties (Oliveira et al., 2020; Oliveira et al., 2021a; Oliveira et al., 2021b). The bottle caps panel is a promising solution for mobile buildings and secondary land transport structures, such as truck floors.…”