Polyurethane has excellent impact resistance and chemical resistance, so polyurethane coatings are often selected to protect helicopter rotors. but the impact of rainwater when flying in rainy weather can still cause great damage to the polyurethane coating. In order to effectively improve the working life of the polyurethane coating in the rain erosion environment. This paper introduces the failure mechanism of rainwater erosion. The factors influencing the rain erosion performance of polyurethane coatings were discussed from internal and external factors respectively. And the equipment, test methods and standards of rain erosion were summarized. Finally, the problem that the rotation arm of the equipment cannot reach the rotation speed of the helicopter rotor and the incident angle of water droplets cannot be changed, and the future development direction is prospected.
Experimental and numerical studies of the 2D woven composite laminates under low-velocity impact with different energy are discussed in this paper. The traditional Hashin failure criteria are improved to cover the failure modes of fiber rupture and delamination. It is found that the damage level depend on the impact energy. The matrix deformation is the main reason of delamination. The simulating results are in good agreement with the experimental phenomenon observed by nondestructive examination (ultrasonic C scanning) and cross-section examination
The properties and structure changes of SiC fiber in high temperature determine the service temperature of the reinforced ceramic matrix composites, so the properties of SiC fibers under high temperature are very important. The SiC-A and SiC-B fibers were treated at 1200, 1350 and 1600°C in Ar atmosphere. Then the tensile strength was measured, the microstructure and composition of the fibers were analyzed by SEM, EDS, XRD and AES. The results show that the tensile strength of SiC-A and SiC-B decrease slowly at 1200 and 1350°C, but decrease rapidly at 1600°C.
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