M Zhang
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7 records found
1
Dynamic vibration is believed to be a basic property of the impacted composite laminates; however, its effect on delamination formation requires further investigation. This study proposes a numerical model in collaborating with ABAQUS, which was calibrated using experimental results, to investigate the effect of plate vibration on delamination formation in composite laminates subjected to two consecutive identical ice or steel projectile impacts with a fixed loading distance. The only variable parameter for the different simulations was the time interval between the two impacts. The loading condition considered in this study is an extreme case where the composite laminate was still vibrating after the first impact when the second impact occurred. The results showed that the delaminations that formed later were significantly affected by the time intervals of the two identical successive ice or steel projectiles. As the vibrated impact points travel from the minimum peak to the adjacent maximum peak during the first vibration period, the newly formed delamination areas monotonically increase with time and vice versa. The change in the maximum contact forces of two identical impacts induced by dynamic vibration is suggested to be a major reason for the discrepancy between the newly formed delamination and previous ones.
In order to study the maintenance strategy of Epoxy Asphalt Concrete (EAC) in low temperature environment, the similarity of four anti-cracking performance indexes (plane strain fracture toughness, bending stiffness modulus, ultimate tensile stress and ultimate elongation linear strain) of EAC were analyzed, and the mathematical model for investigating the relationship between the number of freeze-thaw cycles and the comprehensive evaluation index of the crack resistance of epoxy asphalt mixture (EAM) was established in this paper. At first, the weight of each index is determined by one-way ANOVA. Then the anti-cracking performance of EAC under freezing-thawing condition is evaluated by fuzzy comprehensive evaluation method. The results show that the pavement maintenance bureau needs to carry out the maintenance of epoxy asphalt pavement on steel bridge deck every 30 days (1 month) for ensuring the crack resistance of EAC in winter with low temperature.
Within this framework, the chemical compounds and their reaction products generated under various conditions were studied to reveal the time dependency of molecular microstructures of modified binders. Special attention was given to the evaluation of physiochemical characteristics and the mechanical properties of epoxy-bituminous binders, concluding that the degree of CH and OH was dependent on the level of epoxy modification in bitumen. It was observed that the sulfoxide compounds are the most representative index for assessing the age hardening of epoxy-modified bitumens. Finally, the enhanced resistance against environmental aging in combination with the superior mechanical characteristics (i.e., higher tensile strength, flexibility and enhanced longevity) when the epoxy modification is implemented in bitumen promises a very effective technology for developing long-lasting pavement materials.
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Within this framework, the chemical compounds and their reaction products generated under various conditions were studied to reveal the time dependency of molecular microstructures of modified binders. Special attention was given to the evaluation of physiochemical characteristics and the mechanical properties of epoxy-bituminous binders, concluding that the degree of CH and OH was dependent on the level of epoxy modification in bitumen. It was observed that the sulfoxide compounds are the most representative index for assessing the age hardening of epoxy-modified bitumens. Finally, the enhanced resistance against environmental aging in combination with the superior mechanical characteristics (i.e., higher tensile strength, flexibility and enhanced longevity) when the epoxy modification is implemented in bitumen promises a very effective technology for developing long-lasting pavement materials.