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Fused filament fabrication (FFF) is a popular technique in rapid prototyping capable of building complex structures with high porosity such as cellular solids. The study of cellular solids is relevant by virtue of their enormous potential to exhibit non-traditional deformation mechanisms. The purpose of this study is to exploit the benefits of the FFF technology to fabricate re-entrant honeycomb structures using thermoplastic polyurethane (TPU) to characterize their mechanical response when subjected to cyclic compressive loadings.

Specimens with different volume fraction were designed, three-dimensionally printed and tested in uniaxial cyclic compressions up until densification strain. The deformation mechanism and apparent elastic moduli variation throughout five loading/unloading cycles in two different loading orientations were studied experimentally.

Experimental results demonstrated a nonlinear relationship between volume fraction and apparent elastic modulus. The amount of energy absorbed per loading cycle was computed, exhibiting reductions in energy absorbed of 12%–19% in original orientation and 15%–24% when the unit cells were rotated 90°. A softening phenomenon in the specimens was identified after the first compression when compared to second compression, with reduction in apparent elastic modulus of 23.87% and 28.70% for selected samples V₃ and H₃, respectively. Global buckling in half of the samples was observed, so further work must include redesign in the size of the samples.

The results of this study served to understand the mechanical response of TPU re-entrant honeycombs and their energy absorption ability when compressed in two orientations. This study helps to determine the feasibility of using FFF as manufacturing method and TPU to construct resilient structures that can be integrated into engineering applications as crash energy absorbers. Based on the results, authors suggest structure’s design optimization to reduce weight, higher number of loading cycles (n > 100) and crushing velocities (v > 1 m/s) in compression testing to study the dynamic mechanical response of the re-entrant honeycomb structures and their ability to withstand multiple compressions.

The purpose of this paper is to quantitatively examine if varying household consumption activities at different income levels drove CO₂ emissions to different degrees in Mexico from 1990 to 2014.

The paper applied a simple expenditure-CO₂ emissions elasticity model – a top-down approach – using data from consumption-based CO₂ emission inventories and the “Household Income and Expenditure Survey” and assuming a range of 0.7-1.0 elasticity values.

The paper results show a large carbon inequality among income groups in Mexico throughout the period. The household consumption patterns at the highest income levels are related to significantly more total CO₂ emissions (direct + indirect) than the household consumption patterns at the lowest income levels, in absolute terms, per household and per capita. In 2014, for example, the poorest household decile emitted 1.6 tCO₂ per capita on average, while the wealthiest decile reached 8.6 tCO₂ per capita.

The results suggest that it is necessary to rethink the effect of consumption patterns on climate change and the allocation of mitigation responsibilities, thus opening up complementary options for designing mitigation strategies and policies.

The paper represents an alternative approach for studying CO₂ emissions responsibility in Mexico from the demand side, which has been practically absent in previous studies. The paper thereby opens a way for studying and discussing climate change in terms of consumption and equity in the country.