Abstract
Quadriaxial non-crimp fabric (QNCF) composites are increasingly being used as primary structural materials in aircraft and automotive applications. Predicting the mechanical properties of QNCF lamina is more complicated compared with that of unidirectional (UD) composites, because of the knitting connection of different plies. In this study, to analyze the stiffness and strength of the QNCF composites, a novel modeling strategy for the meso-scale features is presented based on the semi-laminar assumption. Following the view of the mechanical properties of single composite lamina, the complex QNCF layer is decomposed into individual plies. Three different representative unit cells along fiber direction are selected to predict the mechanical performance of QNCF, including in-plane stiffness, damage initiation, and stiffness degradation. To validate the developed modeling strategy, the predictions are compared with existing experimental results, where a good agreement is presented on the prediction of in-plane stiffness and strength. Furthermore, the effect of in-plane fiber distortion, induced by the stitching yarn on the mechanical properties, is studied.
Highlights
Non-crimp fabric (NCF) is constituted by a large amount of fairly straight fiber tows that are placed side by side and bounded by warp-knitting [1]
The numerical predictions of quadriaxial non-crimp fabric (QNCF) lamina are compared with the experimental results of the non-crimped UD laminate in Reference [13]
The complex inter-structure of QNCF is decomposed into some individual ply, and the unit cells along fiber direction are selected
Summary
Non-crimp fabric (NCF) is constituted by a large amount of fairly straight fiber tows that are placed side by side and bounded by warp-knitting [1]. Pre-preg composites, NCF composites have many advantages, such as lower production cost, higher out-of-plane damage tolerance and fracture toughness. It is becoming more popular in the manufacture of complex and thicker parts than UD pre-preg composites [2]. The NCF has two main types, open structure and continuous plies [3]. The fiber tows of continuous plies are laid as closely as possible to reduce the waviness of the fiber tows. Fiber distortion still exists in the plies [4]
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