Based on the principle and fabricating process of Quasi-Isotropic braided composites, the regular pattern of movement of each yarn is analyzed and the inner unit cell model is established in this paper. The real Quasi-Isotropic braiding structure is built using 3D paint software named UG NX4.0. Compressive mechanical properties of 3D Quasi-Isotropic braided composites are also discussed. It is found that the load–deflection curve of the Quasi-isotropic braided composites displays a relatively linear behavior, behaving mostly as the characteristics of shear.
Recycled general-purpose plastic, polypropylene gained general acceptance because of its excellent properties. At the moment, most of experimental tests of short-natural fibers reinforced polymer composites have been concentrated on macro level, lead to un-matured of fine, micro mechanics research work. In this paper, flexural property of short flax fiber-reinforced polypropylene composites was numerical estimated using a FEM model. It has been observed that initial modulus of the composites increases with the rise in fiber volume fraction, while short fiber orientation distribution has little effect on composites; the stress-strain curves almost have no change.
Defects might be formed within braided composites because of the special production process and would have negative effects on the mechanics performance of 3D braided composites. It is important to test and analyses defects to take preventive measures for preventing their formation. In this paper, defects of 3D braided composites were analyzed and methods of nondestructive testing were introduced. Ultrasonic nondestructive testing is one of the earliest methods of nondestructive testing used to evaluate composites. Ultrasonic nondestructive tests of 3D 5-directional braided composites were carried in this paper and the characteristics values were extracted by wavelet analysis method and defect qualitative analysis was implemented.
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