Composite structures used in aircraft need to deal with a wide variety of climatic conditions, such as high temperature, cold temperature, and hydrothermal environment, which probably affects their bearing capability and life expectancy. Additionally, tapered composite laminates are commonly adopted to accommodate the need for varying thicknesses in aircraft structures. Consequently, environmental influence on the tapered composite structures has become a major concern in the utilization of composites. In this work, an experimental program is executed on the tapered composite structures in room temperature atmosphere (RTA), cold temperature dry (CTD), and elevated temperature wet (ETW) conditions separately. The results indicate that the large stress concentration induced by the presence of discontinuous plies in the tapered section motivates the occurrence of delamination at a relatively low load. Environmental exposure does not have a distinct effect on the delamination initiation load. In the hydrothermal environment, the degradation of tensile strength is negligible, and the delamination process as well as the failure pattern of ETW specimens are similar to RTA ones. However, cryogenic conditions result in a severely deteriorating effect on the tensile strength. The failure pattern of CTD specimens exhibits a brittle fracture characteristic and no obvious yield process is observed.
KEYWORDS: Composites, Modeling, 3D modeling, Finite element methods, Failure analysis, Matrices, Design and modelling, Metals, Head, Analytical research
This paper proposed a detailed three-dimensional finite element model (FEM) for composite mechanical joints and developed a parametric, automatic, and process-based tool for rapid modelling and analysis of such joints. The tool allows for batch modelling and analysis for large configurations, significantly improving simulation efficiency. A signal-bolt, signal-lap composite joint was analysed to demonstrate the effectiveness of this tool. In the simulation, the clearance effect was studied and the reduction in stiffness with the increasing clearance was captured by the model. Based on the neat-fit (C1), the overall stiffness of the C2, C3 and C4 configurations obtained by simulation in this paper are reduced by 1.68%, 3.86% and 9.23% respectively. While the stiffness reduction measured by experiments are 1.90%, 7.30%, and 10.4%, respectively.
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