Effect of Nesting on the Permeability of Multilayer Unidirectional Fabrics
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Effect of Nesting on the Permeability of Multilayer Unidirectional Fabrics Jianjun Jiang 1 & Yang Su 1 & Linchao Zhou 1 & Qiang Guo 1 & Chumeng Xu 1 & Guoli Deng 1 & Xing Chen 1 & Xuming Yao 1 & Liangchao Fang 1
Received: 5 September 2016 / Accepted: 8 September 2016 # Springer Science+Business Media Dordrecht 2016
Abstract Nesting of layers is the main source of the variations in permeability values in liquid composite molding (LCM) processes. In this paper, the permeability of unidirectional fabrics was modeled as a function of layer shift and geometrical yarn parameters to study the effect of nesting. Firstly, three different unit cells of two layers were modeled based on the range of layer shift and decomposed into zones of characteristic yarn arrangement, respectively. The overall permeability of each unit cell was then modeled as a mixture of local permeabilities of different zones with the electrical resistance analogy. Secondly, every two adjacent layers were regarded as porous media with different permeabilities. The permeability of multilayer unidirectional fabrics was then modeled with electrical resistance analogy. As the unpredictability of layer shifting in actual process, the statistical characteristics were analyzed theoretically and validated with experimental measurements. Excellent agreement was found between predictions and experiment data. Keywords Fabrics . Permeability . Analytical modelling . Liquid composite moulding
1 Introduction Advanced polymer matrix composites have been widely used in aerospace, marine, and automotive industries [1–4], due to the excellent mechanical properties include high specific strength, high specific stiffness and excellent fatigue performance, etc. But the development is restricted by the high cost of the composite manufacturing. Liquid composite molding (LCM)
* Jianjun Jiang [email protected]
1
Shaanxi Engineering Research Center for Digital Manufacturing Technology, Northwestern Polytechnical University, Xi’an 710072, People’s Republic of China
Appl Compos Mater
processes have become one of mainstream technologies to realize low-cost. In the process, the reinforcement are placed and held stationary by compacting them in a mold cavity and a thermoset resin is injected into the mold to cover the empty spaces between the fibers [5, 6]. The permeability of the fiber preform, which represents the resistance of flowing through a porous medium, is an important parameter influencing the resin impregnation process. Therefore, the characterization of preform permeability is a key issue to optimize process parameters and establish the optimum process window for manufacturing processes to fabricate highquality products [7–9]. Nesting related to layer shift is a geometric phenomenon and inevitably occurs during the process of ply stacking. It generally refers to (partial) filling of inter-yarn voids on the surface of a layer by yarns of an adjacent layer. The nesting of adjacent layers can largely change the flow path and it is one of the main sources of the ob
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