Fracture Flexibility Research Articles

Low and intermediate temperature fracture performance of hot mix asphalt (HMA) reinforced with nano-reduced graphene oxide (NRGO) under freeze-thaw cycles and aging conditions

ABSTRACT This study evaluates the effect of nano-reduced graphene oxide (NRGO) and conditions of short- and long-term (three freeze-thaw cycles (3 FTC)) failure and six days of ageing (6 AM) on bituminous mixtures from the viewpoint of fracture toughness (KIIC and KIIIC) and fracture energy (FEII and FEIII) at ±15 °C. The results showed the fracture stiffness was improved at ±15 °C (under three conditioning states). However, the fracture flexibility was decreased and increased at low and medium temperatures, respectively. At low temperatures, the results indicated that FEIII and KIIC had the lowest resistance under unconditioned and AM conditions, while FEII and KIIC had the lowest resistance under FTC. At intermediate temperatures, FEIII and KIIC under non-conditioned and FTC conditions and FEII and KIIC under AM conditions obtained the lowest resistance. Therefore, it was recommended to check both loading states in determining the shear performance (in-plane and out-of-plane) of asphalt mixtures. Finally, by providing the minimum short- and long-term properties required to control shear and tear cracks, reinforced mixtures lead to increased service life, reduced maintenance costs and improved road safety in cold and tropical regions.

Effect of nano molybdenum disulfide (Nano-MoS2) on fracture behavior of Warm mix asphalt (WMA)

Warm mix asphalt (WMA) has been developed for producing cleaner products than other asphalt mixtures. However, fractures caused by structural factors (microcracks caused by insufficient mixing of bitumen and aggregates at lower construction temperature) and environmental factors (microcracks caused by freeze–thaw cycles (FTCs) and aging process (AP)) lead to the formation of low temperature cracking (LTC) and intermediate temperature cracking (ITC), which is intensified by the loading factor. The present study aimed to evaluate and compare the short and long-term fracture behavior of WMA (containing vertical and angular cracks) using semi-circular bend (SCB) geometries under mode I loading conditions at low and medium temperatures. In order to improve the fracture behavior of WMA, an eco-friendly additive called molybdenum disulfide nanoparticles (Nano-MoS2) was used. The results showed that the mixture reinforced with 0.3 and 0.6% nano-MoS2 had better fracture resistance (Fracture Energy (GF) and Fracture Toughness (KIC)), Fracture Flexibility (Flexibility Index (FI), Toughness Index (TI), and Cracking Resistance Index (CRI)), and fracture toughness (Tensile Stiffness Index (TSI) and Tensile Strength (TS)) than the sample without additives under short-term and long-term conditions at temperatures of −15 and + 15 °C. Under 3FTC, the reduction of three indices KIC, GF, and Pmax (in agreement with the hypothesis), decrease in stiffness (in agreement with the hypothesis), and increase in the flexibility of the mixtures (against the hypothesis) was achieved. In addition, the increase of the three indices KIC, GF, and Pmax (against the hypothesis), increase of stiffness (agree with the hypothesis), and decrease of flexibility of the mixtures (agree with the hypothesis) were obtained under 6AP. After the addition of nano-MoS2 to the WMA, a large part of the reduction in the fracture indices was compensated due to the application of FTD cycles. Therefore, the mixture reinforced with nano-MoS2 had better long-term performance under mode I at low and medium temperatures (compared to the sample without additives and at the beginning of the design year). On the other hand, the long-term performance results showed that SCB samples containing vertical and angular cracks were more affected by 3FTC than 6AP. This result indicated the use of FTD cycles to evaluate the long-term performance of WMA mixture to achieve a better design.

Fabrication of core–shell liquid metal@silica nanoparticles for enhanced mechanical, dielectric and thermal properties of silicone rubber

Core–shell amino-modified silica-coated LM nanoparticles (LM@SiO2–NH2) for reinforcing silicone rubber.

The Laboratorial Study of Fracture Energy Release Rate of the Reservoir Ice Layer

The fracture energy release rate , which is the important parameter of ice pressure calculation model that is built on energy balance method, is the fracture mechanics performance of ice material. It is related with these factors such as ice material temperature T, which must be measured by experiment. It is the experimental method of fracture mechanics used in this paper. These ice specimens on the different thickness T were tested with fracture mechanics method at low-temperature testing machine, to obtain the fracture flexibility change rate of ice body which contains pre-crack and the values of under different conditions of T, which could determine fracture energy release rate of ice body during the ice pressure generated, which provide the necessary experimental data to establish ice layer pressure calculation model for the application of energy balance method.