Abstract:Effect of thermally induced microcracks on mechanical performance of a space grade laminated sandwich panel is investigated. A simple non-contact setup using liquid nitrogen is developed to subject the material to low temperature of −170℃ with cooling rate of 24℃/min. Then the samples are exposed to the elevated temperature of 150℃ inside oven. Microcracks formation and propagation are monitored through microscopic observation of cross-section during the cycling. Flatwise tensile test is performed after a numb… Show more
“…This could be attributed to the local deformations of pellets walls and rapid escape of air from the voids under compressive loads that otherwise might not occur under tensile loads. 26 In loading condition (2), the test results revealed a relatively small reduction of the tensile modulus, that is, about 5.72% after exposure to 45 thermal cycles. Fluctuations of the failure load with a maximum difference of 9% with no specific trend were observed in this case.Figure 7.Tensile load-displacement curves of specimens exposed to various loading scenarios: (a) thermal cycles and (b) high-temperature loading, and (c) high-temperature loading after 45 thermal cycles.Figure 8.Tensile failure of EPS foam.…”
Section: Resultsmentioning
confidence: 95%
“…This could be attributed to the local deformations of pellets walls and rapid escape of air from the voids under compressive loads that otherwise might not occur under tensile loads. 26 In loading condition (2), the test results revealed a relatively small reduction of the tensile modulus, that is, about 5.72% after exposure to 45 thermal cycles. Fluctuations of the failure load with a maximum difference of 9% with no specific trend were observed in this case.…”
Section: Tensile Test Resultsmentioning
confidence: 95%
“…In addition, no studies can be found on the effects of temperature cycles on the mechanical properties of EPS foam. Some studies have investigated these effects in other materials like concrete, polymer laminates, and others, [26][27][28][29][30] which showed that the mechanical properties of the material degrade appreciably after exposure to several thermal cycles. Grammatikos et al 30 tested the response of glass fiber reinforced polymer (GFRP) laminates under thermal cyclic loading (À10°C to 20°C) and measured significant degradation of the mechanical properties.…”
Understanding the effects of high temperature and thermal cycles on the mechanical properties of expanded polystyrene (EPS) foam is critical for its use in sandwich panels. This paper presents an experimental investigation of these effects in typical environmental conditions that exist in construction applications. A total of 117 small specimens were cut from metal-faced sandwich panels with EPS core and were exposed to different numbers of thermal cycles and/or sustained high temperatures. The specimens were then loaded under compression, tension, and four-point bending for evaluating the degradation of the mechanical properties of the foam. The thermal cycles reflect typical surface temperature during daily summer conditions, with a period of 24 h each and with a temperature varying between 24°C to 80°C. The results show that the modulus of elasticity of EPS foam in compression reduced by about 38% after exposure to thermal cycles for 45 days, whereas the tensile and shear moduli reduced by about 5.7% and 13.8%, respectively. Exposure to sustained high temperature after thermal cycles led to larger degradation of the elastic and shear moduli in the range of 38%–50%. These degradations can lead to early failures in applications that rely on the EPS foam as a structural component like in insulating sandwich panels.
“…This could be attributed to the local deformations of pellets walls and rapid escape of air from the voids under compressive loads that otherwise might not occur under tensile loads. 26 In loading condition (2), the test results revealed a relatively small reduction of the tensile modulus, that is, about 5.72% after exposure to 45 thermal cycles. Fluctuations of the failure load with a maximum difference of 9% with no specific trend were observed in this case.Figure 7.Tensile load-displacement curves of specimens exposed to various loading scenarios: (a) thermal cycles and (b) high-temperature loading, and (c) high-temperature loading after 45 thermal cycles.Figure 8.Tensile failure of EPS foam.…”
Section: Resultsmentioning
confidence: 95%
“…This could be attributed to the local deformations of pellets walls and rapid escape of air from the voids under compressive loads that otherwise might not occur under tensile loads. 26 In loading condition (2), the test results revealed a relatively small reduction of the tensile modulus, that is, about 5.72% after exposure to 45 thermal cycles. Fluctuations of the failure load with a maximum difference of 9% with no specific trend were observed in this case.…”
Section: Tensile Test Resultsmentioning
confidence: 95%
“…In addition, no studies can be found on the effects of temperature cycles on the mechanical properties of EPS foam. Some studies have investigated these effects in other materials like concrete, polymer laminates, and others, [26][27][28][29][30] which showed that the mechanical properties of the material degrade appreciably after exposure to several thermal cycles. Grammatikos et al 30 tested the response of glass fiber reinforced polymer (GFRP) laminates under thermal cyclic loading (À10°C to 20°C) and measured significant degradation of the mechanical properties.…”
Understanding the effects of high temperature and thermal cycles on the mechanical properties of expanded polystyrene (EPS) foam is critical for its use in sandwich panels. This paper presents an experimental investigation of these effects in typical environmental conditions that exist in construction applications. A total of 117 small specimens were cut from metal-faced sandwich panels with EPS core and were exposed to different numbers of thermal cycles and/or sustained high temperatures. The specimens were then loaded under compression, tension, and four-point bending for evaluating the degradation of the mechanical properties of the foam. The thermal cycles reflect typical surface temperature during daily summer conditions, with a period of 24 h each and with a temperature varying between 24°C to 80°C. The results show that the modulus of elasticity of EPS foam in compression reduced by about 38% after exposure to thermal cycles for 45 days, whereas the tensile and shear moduli reduced by about 5.7% and 13.8%, respectively. Exposure to sustained high temperature after thermal cycles led to larger degradation of the elastic and shear moduli in the range of 38%–50%. These degradations can lead to early failures in applications that rely on the EPS foam as a structural component like in insulating sandwich panels.
“…Furthermore, in the presence of these micro-cracks, volatiles and moisture entrapped inside the structure escape easily. Hence, the mass reduces until all volatile components are escaped from the structure [46][47][48][49][50][51][52].…”
Section: High Thermal Cyclingmentioning
confidence: 99%
“…Furthermore, in the presence of these micro-cracks, volatiles and moisture entrapped inside the structure escape easily. Hence, the mass reduces until all volatile components are escaped from the structure [46][47][48][49][50][51][52]. When the structure is made of composite material that consists of fiber and matrix, both have different thermal expansion characteristics.…”
This review paper discusses the effect of polymers, especially thermoplastics, in environments with low earth orbits. Space weather in terms of low earth orbits has been characterized into seven main elements, namely microgravity, residual atmosphere, high vacuum, atomic oxygen, ultraviolet and ionization radiation, solar radiation, and space debris. Each element is discussed extensively. Its effect on polymers and composite materials has also been studied. Quantification of these effects can be evaluated by understanding the mechanisms of material degradation caused by each environmental factor along with its synergetic effect. Hence, the design elements to mitigate the material degradation can be identified. Finally, a cause-and-effect diagram (Ishikawa diagram) is designed to characterize the important design elements required to investigate while choosing a material for a satellite’s structure. This will help the designers to develop experimental methodologies to test the composite material for its suitability against the space environment. Some available testing facilities will be discussed. Some potential polymers will also be suggested for further evaluation.
The production of lunar regolith composites is a promising venture, especially when enabled by extrusion-based additive manufacturing techniques such as direct ink write. However, both three-dimensional (3D) printing production and usage of polymer composites containing regolish on the lunar surface are challenges due to harsh environmental conditions such as severe thermal cycling. While thermal degradation in polymer composites under thermal cycling has been studied, there is limited understanding of how polymer properties impact the mechanical performance of lunar regolith composites when both printing and usage are carried out under extreme thermal conditions. Here, we aim to bridge that gap through the creation of composites containing a lunar Highlands regolith simulant suspended in an ultraviolet (UV) curable binder, which were printed at −30 °C and thermally cycled between weekly lunar day (127 °C) and weekly night (−190 °C) temperatures. We validate that thermal stresses cause both physical and chemical degradation since the regolith simulant composites become stiffer, more porous, and show yellowing after exposure to thermal cycling. Moreover, we indicate that chemical degradation mechanisms seem to compete with residual polymerization in certain formulations. We attribute this phenomenon to partial crystallization of monomer species during printing at −30 °C, resulting in low vinyl bond conversion during initial curing. The results presented here shed light on the intricate interplay between thermal stresses, uncured polymer properties, and degradation mechanisms, which can help guide future use cases of regolith composites for lunar infrastructure needs.
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