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Pei X.,Tianjin Polytechnic University | Shang B.,Tianjin Polytechnic University | Shang B.,Aerospace Shenzhou Aerial Vehicle Ltd | Li J.,Tianjin Polytechnic University | And 3 more authors.
Cailiao Yanjiu Xuebao/Chinese Journal of Materials Research

Interlaminar shear properties along directions of 0° and 90° of resin composites reinforced with multilayer-connected biaxial weft knitted (MBWK) fabrics of carbon fibers, were investigated by shear test. The test composites involve three, four and five layer-connected MBWK fabrics respectively. It was found that the shear strength increased with the increasing fiber volume fraction. The variation of the interlaminar shear load-deflection curves tended to be linear. When the load reached the maximum value the load-deflection curve dropped suddenly, and the composites showed brittle fracture. The analysis of fracture surface showed that the structure of reinforcement has significant effect on shear properties of MBWK fabrics reinforced composites. The shear failure mode of the composites was delaminating. Mean-while, the cracking preferred mainly along the delaminating at the interface between the fabric groups. ©, 2015 All right reserved. Source

Pei X.,Tianjin Polytechnic University | Pei X.,University of South Australia | Shang B.,Tianjin Polytechnic University | Shang B.,Aerospace Shenzhou Aerial Vehicle Ltd | And 3 more authors.
Composites Part B: Engineering

Three kinds of multilayer-connected biaxial weft knitted (MBWK) fabric reinforced composites are studied here, namely three-layer-connected, four-layer-connected, and five-layer-connected biaxial weft knitted fabrics. The compression properties of the MBWK fabric reinforced composites are characterized in the 0° and 90° directions by different carbon fiber volume fractions (Vf). Macro-fracture morphology and scanning electron micrograph (SEM) images are used to understand the deformation and failure mechanisms. Experimental results show that in the range of Vf, the structure of the reinforcement has significant effects on the compression properties of MBWK fabric reinforced composites. The major failure mode of the composites is shear failure, and the cracking of the composites focuses mainly on the delamination of the fabrics between the groups. © 2016 Elsevier Ltd. All rights reserved. Source

Wang H.,Aerospace Shenzhou Aerial Vehicle Ltd | Chen M.,Aerospace Shenzhou Aerial Vehicle Ltd
Yingyong Lixue Xuebao/Chinese Journal of Applied Mechanics

The helicopter rotor sensitivity of aeroelastic stability, modal frequency, auto-rotary inertia, blade quality and blade dynamic stresses is derived, which is based on the helicopter rotor aeroelastic dynamics, by combining the perturbation method of sensitivity analysis and the direct analytical chain rules sensitivity analysis techniques. Calculation results obtained indicate that by using sensitivity analysis of model optimization and the direct optimization, dynamic stress is reduced 1.2%, total quality of rotor blade reduction of 0.84%, optimization time is shortened by 2.73 times value. The effectiveness of the sensitivity analysis technique for helicopter rotor aeroelastic dynamics optimization design convergence speed and the optimum results is demonstrated. Source

Zhang T.,Beihang University | Zhou H.,Aerospace Shenzhou Aerial Vehicle Ltd | Shi W.,Aerospace Shenzhou Aerial Vehicle Ltd | Yan Y.,Beihang University
Fuhe Cailiao Xuebao/Acta Materiae Compositae Sinica

The Z-pinned woven composite unit cell models of lamina and laminate were developed based on the plain woven composite micro-structure with carbon fiber reinforced after Z-pin inserted. The influence of Z-pin diameter and distribution interval on the in-plane longitudinal tensile mechanical properties was predicted. The stress concentration around Z-pin in the Z-pinned woven composite unit cell model was recognized. The strength would be reduced after unit cell been failed due to the stress concentration. The process of Z-pin pulled out from laminated plates was simulated. The pull-out force versus displacement curves with different Z-pin diameters and thicknesses of separate sub layer were obtained. The double cantilever beam (DCB) with nonlinear spring element and virtual crack closure technique (VCCT) was developed. The mode I crack propagation of Z-pinned laminate was simulated. It was concluded that equivalent mode I energy release rate GIC of the laminate and its waviness amplitude were larger caused by larger Z-pin diameter. Moreover, the denser the Z-pin distribution was, the larger GIC was and the smaller its wavelength was. Source

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