Numerical Investigation of T-joints with 3D Four Directional Braided Composite Fillers Under Tensile Loading
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Numerical Investigation of T-joints with 3D Four Directional Braided Composite Fillers Under Tensile Loading Xiao-kang Li 1 & Zhen-guo Liu 1 & Long Hu 1 & Yi-bo Wang 1 & Bing Lei 1 & Xiang Huang 1
Received: 3 July 2016 / Accepted: 17 July 2016 # Springer Science+Business Media Dordrecht 2016
Abstract Numerical studied on T-joints with three-dimensional four directional (3D4D) braided composite fillers was presented in this article. Compared with conventional unidirectional prepreg fillers, the 3D braided composite fillers have excellent ability to prevent crack from penetrating trigone fillers, which constantly occurred in the conventional fillers. Meanwhile, the 3D braided composite fillers had higher fiber volume fraction and eliminated the fiber folding problem in unidirectional prepreg fillers. The braiding technology and mechanical performance of 3D4D braided fillers were studied. The numerical model of carbon fiber T-joints with 3D4D braided composite fillers was built by finite element analysis software. The damage formation, extension and failing process of T-joints with 3D4D braided fillers under tensile load were investigated. Further investigation was extended to the effect of 3D4D braided fillers with different braiding angles on mechanical behavior of the T-joints. The study results revealed that the filling area was the weakest part of the T-joints where the damage first appeared and the crack then rapidly spread to the glue film around the filling area and the interface between over-laminate and soleplate. The 3D4D braided fillers were undamaged and the braiding angle change induced a little effect on the bearing capacity of T-joints. Keywords 3D4D braided fillers . T-joints . numerical simulation . crack damage . braiding angle
* Zhen-guo Liu [email protected]
1
School of Aeronautic Science and Engineering, Beihang University (BUAA), Beijing 100191, People’s Republic of China
Appl Compos Mater
1 Introduction T-joints, with the progress of manufacturing technique, have attracted more and more attention from the aerospace industry. The joints were potentially the weakest points and determined the integral structural efficiency. Examples of airframe assemblies include the skin-to-rib and skin-to-spar joints. Many researchers have investigated into the behavior of these components and in particular the failure mechanism of composite laminate and composite T-joints [1–7]. Dharmawan and Thomson [5] reported that the critical strains were significantly affected by the joint geometry and the effect of debonding between the fillers and over-laminate were also reported. Cui [6] reported that the critical regions of damage initiations were the fillet and the arc transition plies of the composite T-joints. The mechanical performance of the T-joint was determined by parameters of the trigone fillet, such as arc radius, ply stacking and thickness of L-ribs, mechanical properties of the fillet facial properties and so on. Cheng et al. [7] carried out tension and shear tests on composite cross-joints which
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