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Araya-Letelier, G., Antico, F. C., Carrasco, M., Rojas, P., & Garcia-Herrera, C. M. (2017). Effectiveness of new natural fibers on damage-mechanical performance of mortar. Constr. Build. Mater., 152, 672–682.
Abstract: Addition of fibers to cement-based materials improve tensile and flexural strength, fracture toughness, abrasion resistance, delay cracking, and reduce crack widths. Natural fibers have recently become more popular in the construction materials community. This investigation addresses the characterization of a new animal fiber (pig hair), a massive food-industry waste worldwide, and its use in mortars. Morphological, physical and mechanical properties of pig hair are determined in order to be used as reinforcement in mortars. A sensitivity analysis on the volumes of fiber in mortars is developed. The results from this investigation showed that reinforced mortars significantly improve impact strength, abrasion resistance, plastic shrinkage cracking, age at cracking, and crack widths as fiber volume increases. Other properties such as compressive and flexural strength, density, porosity and modulus of elasticity of reinforced mortars are not significantly affected by the addition of pig hair. (C) 2017 Elsevier Ltd. All rights reserved.
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Labra, F. A., San Martin, V. A., Jahnsen-Guzman, N., Fernandez, C., Zapata, J., Garcia-Huidobro, M. R., et al. (2022). Metabolic rate allometry in intertidal mussels across environmental gradients: The role of coastal carbonate system parameters in mediating the effects of latitude and temperature. Mar. Pollut. Bull., 184, 114149.
Abstract: We assess the role of direct and indirect effects of coastal environmental drivers (including the parameters of the carbonate system) on energy expenditure (MR) and body mass (M) of the intertidal mussel, Perumytilus pur-puratus, across 10 populations distributed over 2800 km along the Southern Eastern Pacific (SEP) coast. We find biogeographic and local variation in carbonate system variables mediates the effects of latitude and temperature on metabolic rate allometry along the SEP coast. Also, the fitted Piecewise Structural Equation models (PSEM) have greater predictive ability (conditional R2 = 0.95) relative to the allometric scaling model (R2 = 0.35). The largest standardized coefficients for MR and M were determined by the influence of temperature and latitude, followed by pCO2, pH, total alkalinity, and salinity. Thus, physiological diversity of P. purpuratus along the SEP coast emerges as the result of direct and indirect effects of biogeographic and local environmental variables.
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Lagos, N. A., Benitez, S., Grenier, C., Rodriguez-Navarro, A. B., Garcia-Herrera, C., Abarca-Ortega, A., et al. (2021). Plasticity in organic composition maintains biomechanical performance in shells of juvenile scallops exposed to altered temperature and pH conditions. Sci. Rep., 11(1), 24201.
Abstract: The exposure to environmental variations in pH and temperature has proven impacts on benthic ectotherms calcifiers, as evidenced by tradeoffs between physiological processes. However, how these stressors affect structure and functionality of mollusk shells has received less attention. Episodic events of upwelling of deep cold and low pH waters are well documented in eastern boundary systems and may be stressful to mollusks, impairing both physiological and biomechanical performance. These events are projected to become more intense, and extensive in time with ongoing global warming. In this study, we evaluate the independent and interactive effects of temperature and pH on the biomineral and biomechanical properties of Argopecten purpuratus scallop shells. Total organic matter in the shell mineral increased under reduced pH (similar to 7.7) and control conditions (pH similar to 8.0). The periostracum layer coating the outer shell surface showed increased protein content under low pH conditions but decreasing sulfate and polysaccharides content. Reduced pH negatively impacts shell density and increases the disorder in the orientation of calcite crystals. At elevated temperatures (18 degrees C), shell microhardness increased. Other biomechanical properties were not affected by pH/temperature treatments. Thus, under a reduction of 0.3 pH units and low temperature, the response of A. purpuratus was a tradeoff among organic compounds (biopolymer plasticity), density, and crystal organization (mineral plasticity) to maintain shell biomechanical performance, while increased temperature ameliorated the impacts on shell hardness. Biopolymer plasticity was associated with ecophysiological performance, indicating that, under the influence of natural fluctuations in pH and temperature, energetic constraints might be critical in modulating the long-term sustainability of this compensatory mechanism.
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Martel, S. I., Fernandez, C., Lagos, N. A., Labra, F. A., Duarte, C., Vivanco, J. F., et al. (2022). Acidification and high-temperature impacts on energetics and shell production of the edible clam Ameghinomya antiqua. Front. Mar. Sci., 9, 972135.
Abstract: Warming and ocean acidification are currently critical global change drivers for marine ecosystems due to their complex and irreversible effects on the ecology and evolution of marine communities. Changes in the chemistry and the temperature of the ocean impact the biological performance of marine resources by affecting their energy budget and thus imposing energetic restrictions and trade-offs on their survival, growth, and reproduction. In this study, we evaluated the interplaying effects of increased pCO(2) levels and temperature on the economically relevant clam Ameghinomya antiqua, an infaunal bivalve inhabiting a wide distributional range along the coast of Chile. Juvenile clams collected from southern Chile were exposed to a 90-day experimental set-up emulating the current and a future scenario projeced to the end of the current century for both high pCO(2)/low-pH and temperature (10 and 15 degrees C) projected for the Chilean coast. Clams showed physiological plasticity to different projected environmental scenarios without mortality. In addition, our results showed that the specimens under low-pH conditions were not able to meet the energetic requirements when increased temperature imposed high maintenance costs, consequently showing metabolic depression. Indeed, although the calcification rate was negative in the high-pCO(2) scenario, it was the temperature that determined the amount of shell loss. These results indicate that the studied clam can face environmental changes for short-term periods modifying energetic allocation on maintenance and growth processes, but with possible long-term population costs, endangering the sustainability of an important benthic artisanal fisheries resource.
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Vasco, D. A., Munoz-Mejias, M., Pino-Sepulveda, R., Ortega-Aguilera, R., & Garcia-Herrera, C. (2017). Thermal simulation of a social dwelling in Chile: Effect of the thermal zone and the temperature-dependant thermophysical properties of light envelope materials. Appl. Therm. Eng., 112, 771–783.
Abstract: As in most countries, Chile exhibits a continuous growth of energy demand, although nowadays the country does not have enough conventional energy sources to supply it. For this reason, energy saving approaches in the residential sector have been encouraged. One of the solutions to improve the energy performance of the buildings is to decrease wasting energy through the building's envelope, therefore the thermal properties of materials used in building envelopes must be analyzed to evaluate the thermal response of houses. Normally, the thermal envelope of a social house in Chile is made of brick or wood along with light materials such as fiber cement, plasterboard, and thermal insulating materials as polystyrene foam. The experimental part of this work deals with the measurement of the thermal conductivity and thermal diffusivity of the aforementioned light materials in a temperature range from -5 degrees C to 40 degrees C through the transient line heat source method. The experimental results allowed the identification of 10-20% variation of those thermophysical properties. The response of the thermal envelope and the inner temperature of a social dwelling under seven different climatological conditions was evaluated through transient simulations with EnergyPlus. The results allowed to identify that the dwellings located in hotter zones are prone to having higher temperatures than the comfort temperature, and the recommendations of the thermal regulations in Chile are more effective in the colder thermal zones 6 and 7. (C) 2016 Elsevier Ltd. All rights reserved.
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Vukasovic, T., Vivanco, J. F., Celentano, D., & Garcia-Herrera, C. (2019). Characterization of the mechanical response of thermoplastic parts fabricated with 3D printing. Int. J. Adv. Manuf. Technol., 104(9-12), 4207–4218.
Abstract: 3D printing has gained great popularity due to its main feature of manufacturing complex geometries. The building process by adding successive layers generates mechanical properties that depend on the printing parameters, where build orientation is one of the most relevant factors. Due to this, the characterization of the mechanical response of these pieces is a challenging task of practical importance to estimate their lifespan. The aim of this study is to characterize the mechanical behavior and define a 3D constitutive model of polymer materials commonly used in 3D printing manufacturing. Hence, ABS and PLA were used with a low-cost desktop printer with which specimens were manufactured in two orthogonal orientations: flat and upright. Tensile and compression tests were performed to this end, where the Young's modulus, yield, and maximum stresses were determined. In the tensile tests, the samples with vertical (upright) orientation showed lower values in the evaluated mechanical properties than the corresponding to the horizontal (flat) orientation. However, no significant difference caused by the printing orientations was observed in the compression tests. Different values of Young's modulus and maximum strength were found between tensile and compression tests for the same material and orientation. Moreover, in order to describe the observed material response, a linear isotropic bimodular model is proposed. This constitutive model, which is fed with the previously obtained tensile and compression data, is used in the simulation of a four-point bending test where it is found to adequately represent the experimentally measured elastic behavior in the load-deflection curve. Thus, the combination of experiments and a bimodular constitutive model contributes to making better predictions of the mechanical response of structures made with 3D printing.
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