Manufactured sand is one of the effective ways to alleviate the extreme shortage of natural sand in the construction industry. This paper uses granite and limestone manufactured sand to study the effect of high fines content on the durability of high-strength manufactured sand concrete, and analyzes its influence mechanism by combining macro and micro test methods. The results show that the carbonation depth of manufactured sand concrete is the smallest when the fines content is 10%. When the fines content is less than 15%, the chloride and sulfate impermeability of concrete are improved effectively. Through macroscopic and microscopic tests, it is found that the main reason why fines can improve the durability of concrete is the filling effect. Too much fines will inhibit the hydration of cement and adversely affect the durability of concrete. Therefore, the fines content of high-strength manufactured sand concrete should be controlled within 5~15%, and the durability is the best when the fines content is 10%.

In this paper, a self-adaptive flange is proposed for the wind turbine shrouded by a flanged diffuser to reduce the wind loads acting on the flanged diffuser at high wind velocities. The self-adaptive flange can maintain the advantages of the flanged diffuser at wind velocities lower than the rated velocity and reduce the wind loads acting on the diffuser and blades at higher wind velocities. Numerical analyses of fluid-structure interactions are carried out to investigate the flow field around the diffuser with a self-adaptive flange and the variation of wind load acting on the diffuser due to the reconfiguration of the self-adaptive flange at various wind velocities. Numerical results show that the wind load acting on the total flanged diffuser can be reduced by about 35% at 60 m/s due to the reconfiguration of the self-adaptive flange.

This study proposes a novel tab for the tensile testing of unidirectional (UD) carbon fiber-reinforced thermoplastic polyamide 6 (CF/PA6) to reduce stress concentration at the tab end. The length of the new tab is identical to that of the UD CF/PA6 specimen to avoid a sudden change in geometry that is typically observed in a conventional tab end. Additionally, three types of UD CF/PA6 laminates from different manufacturers are used to fabricate tensile specimens. Specimens with a new tab and a conventional nontapered tab are tested under quasi-static tension. Finite element simulations of tensile testing are also performed for specimens with two types of tabs. The experimental and simulation results demonstrate that the newly designed tab reduces the stress concentration at the tab end by approximately 10% and improves the estimates of tensile strength for the UD thermoplastic composite laminates.

The effect of off-axis ply on the tensile properties of unbalanced symmetric [0/θ]_ns laminates was explored through experimental and numerical analysis. Six CFRP [0/θ]_2s plies with different off-axis angles θ were fabricated for tensile tests. In situ observations of the damage to the laminates were conducted to investigate the initiation and progressive growth of the laminates during the tension tests. The fiber fractures, crack initiation, and progressive propagation were analyzed by observing the free edge of the laminates, and the difference in damage behavior caused by different off-axis angles was investigated. All the six [0/θ]_2s plies with off-axis angles θ ranging from 15° to 90° showed approximate linear stress–strain responses in the tensile tests. Matrix cracks were not observed prior to the final catastrophic failure in the off-axis layers of the [0/θ]_2s laminates with a θ in the range of 15–60°. Finite element analysis (FEA) of the [0/θ]_s plies was conducted using a 3D micromechanical model, in which matrix cracking and fiber-matrix debonding in the off-axis layer were simulated using a cohesive interface element. Three micromechanical crack-free, cohesive interface, and initial crack models were analyzed to predict the influence of the matrix cracks inside the off-axis layer on the damage behavior of the [0/θ]_s laminates. The numerical results from the initial crack micromechanical model show a lower bound of the tensile strength of the [0/θ]_s plies. A high stress concentration is observed adjacent to the cracked off-axis layer, inducing a tensile strength loss of about 20%.