Abstract The bolt holes of multi-bolt composite joints have bearing deformation caused by bolt loads and hole tensile deformation resulted from bypass loads. However, the hole tensile deformation was neglected in the existing stiffness method, because the stiffness formula of laminates without hole was applied for the joined hole laminates, which leads to a relatively rough prediction of the bolt load distribution, especially for the multi-bolt joints with larger numbers of bolts, in which the bypass loads are much bigger than the bearing loads. To improve the accuracy of the existing stiffness method, a modified stiffness method was proposed. In this method, based on the effect mechanism of the hole tensile deformation on the deformation compatibility condition, a concept of an additional stiffness corresponding to the hole tensile deformation and its calculation method were presented to modify the deformation compatibility equation. The bolt-load ratios predicted by the modified method and the existing method were compared with those obtained from FE models. It follows that the modified method possesses higher precision, and the improvement of the prediction accuracy is more conspicuous as the number of the bolts increases. The presented method shows overwhelming advantages over the existing method.
Aircraft structures consist of largely thin sheets stiffened by different shape of stringers. If damage occurs to the thin sheet, a normal procedure taken is to remove the damage area usually in the shape of rectangular hole which is rounded at the corners to reduce the stress concentration. The area is then reinforced with a repair patch riveted to the sheet. Riveted joint is one of the most methods that are usually used by aircraft manufacturer to repair an aircraft structure. The important th...
Last. Jianyu Zhang(Chongqing University)H-Index: 25
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Abstract A bi-material property method was proposed to describe mechanical properties of the unidirectional composite lamina. It divided the lamina into the fiber layer and the resin layer, which have different material properties and are responsible for the intra-laminar and inter-laminar properties, respectively. Furthermore, a finite element modelling method with the composite lamina simulated by the bi-material property method was presented. Combined with a Hashin-type failure criterion and ...
Abstract A test method was presented to measure the bolt load distribution in the progressive damage process of multi-bolt composite joints, which exhibits continuous changes with the damage propagation in composite laminates. Based on the repeated loading-unloading cycles, bolt shear loads of a double-lap, three-bolt joint were tested by alternately using modified instrumented bolt-nut pairs and aircraft-grade fasteners, from which the bolt load redistribution history was achieved. In addition,...
Last. Yulong Li(NPU: Northwestern Polytechnical University)H-Index: 23
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Abstract A multi-scale simulation framework based on finite element method is developed to model the impact failure behavior of triaxially braided composite. The model integrates micromechanical model, meso-mechanical model and macro subcell model for the purpose of determining effective properties of fiber tows, estimating effective properties of subcell components, and simulating impact failure behavior of a braided composite structure, respectively. The meso-mechanical model compares excellen...
Last. Jianyu Zhang(Chongqing University)H-Index: 25
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Abstract This paper presents a stochastic bolt load distribution analysis method of composite single-lap multi-bolt joints by using an improved three-stage spring-based method and Monte Carlo simulation. In the proposed method, the random properties of tightening torque, bolt-hole clearance, lamina properties and geometric parameters were involved. The allowable manufacturing tolerance band of parameters and clearance fit were considered, and a combining distribution function consisting of binom...
Abstract A detailed interpretation of load distribution in composite single-lap bolted joints is presented based on theoretical, experimental and numerical investigations. Modified instrumented bolts (MIBs) were used to measure bolt shear loads consisting of the bolt bearing load and the friction force between the laminate and nut. The bolt-load carrying mechanism in single-bolt joints and the load transfer mechanism in multi-bolt joints with various tightening torques and bolt-hole clearances w...
#1Bibekananda Mandal(IITR: Indian Institute of Technology Roorkee)H-Index: 4
#2Anupam Chakrabarti(IITR: Indian Institute of Technology Roorkee)H-Index: 25
Abstract A three dimensional (3D) progressive damage model (PDM) is developed for the failure assessment of fibre reinforced plastic (FRP) composite bolted joints subjected to bolt preloads. Material constitutive equations and material damage model are defined in a user-subroutine UMAT which is integrated with the finite element (FE) software ABAQUS. Fibre and matrix failure in tension, compression or in shear along with delamination failure criteria are incorporated in the present numerical mod...
Abstract An enhanced spring-mass stiffness model was proposed, which was based on the supposition that the transverse shear stress under preload satisfies conical and spherical envelope, to predict the stiffness of the single-lap single-bolt composite joint with considering assembly gap and gap shimming. The validation experiments were conducted for different configurations. It shows that the analytical results were all in good agreement with the experimental results. Meanwhile, experimentally v...
Last. Wei Feng(NPU: Northwestern Polytechnical University)H-Index: 5
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Abstract In this paper, a theoretical 4-stage shear model for a single-lap torqued bolted-joint with clearance is proposed. The deformation mechanism of the bolted-joint indicates that the contact status is the key factor for the nonlinearity of the load-displacement curve. On the basis of the contact status, the expression of this model and its parameters are proposed. Compared with the previous Tri-linear model, this model is improved on three aspects. First, the 1st stage of the model has bee...
ABSTRACTThis article proposes a novel collaborative optimization (NCO) framework that uses a persuasive multi-agent negotiation method for satellite system design. Satellite system design is a typical multi-disciplinary design optimization problem. The traditional collaborative optimization (CO) is a competitive method but has the disadvantage of inefficient convergence caused by the interdisciplinary compatibility constraints in system-level optimization. By introducing the multi-agent negotiat...
Last. Enquan Liang(Shanghai Aircraft Design and Research Institute)H-Index: 2
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Multibolt composite joints are widely used in aircraft structures. The determination of the pin-load distribution among the bolts is a critical step in the failure prediction of bolted joints. In this paper, a two-dimensional model of the multibolt composite structure is established for the pin-load distribution analysis. Its accuracy is validated by experimental results and the results from a 3D finite element model. Based on the determined pin-load distribution, FE models for a laminated plate...
Due to the brittle feature of carbon fiber reinforced plastic laminates, mechanical multi-joint within these composite components show uneven load distribution for each bolt, which weaken the strength advantage of composite laminates. In order to reduce this defect and achieve the goal of even load distribution in mechanical joints, we propose a machine learning-based framework as an optimization method. Since that the friction effect has been proven to be a significant factor in determining bol...
Abstract In this study, a new fast approach to predict the net-tension failure strength of multi-bolt composite joints was developed based on finite fracture mechanics and p-version parametric finite element methods. In the proposed approach, stress distribution and stress intensity factor are obtained using the principle of superposition, based on which the problem can be divided into open hole tension and hole bearing problems. The stress distribution and stress intensity factor are determined...
Last. Francesco Vivio(University of Rome Tor Vergata)H-Index: 14
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Abstract The general definition of a novel finite element for structural analysis of composite bolted joints is presented. The work aims to define an accurate and computationally efficient simulation tool for multi-jointed composite structures characterized by a low entry of degrees of freedom. The modeling approach exploits the full stiffness evaluation of the bolted region from the analytical standpoint. Two main stiffness contributions are defined: the first one is the elasticity of the plate...
#1Maoqing Fu(HIT: Harbin Institute of Technology)H-Index: 4
#2Guodong Fang(HIT: Harbin Institute of Technology)H-Index: 15
Last. Jun Liang(BIT: Beijing Institute of Technology)H-Index: 24
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Abstract An improved shell-fastener model is proposed to study the mechanical behavior of C/SiC composite bolted joints with the rough surface (millimetric magnitude). Based on the axial compressive experiment, the normal contact stiffness is obtained by a modified fractal normal contact model, which is also validated by using a solid FE model and a hybrid FE model (shell-fastener and solid nuts). The equivalent axial stiffness and shear stiffness used in the shell-fastener model for the bolted ...
Abstract This study presents an investigation into the failure mechanism and strength improvement of a sandwich composite T-joint bonded and reinforced by fasteners made of thermal plastic composite. The T-joint subjected to pulling load was analysed by numerical simulation and experiment methods. Cohesive zone model (CZM) and Hashin damage criteria were used in the FE analysis to simulate the crack propagation. According to the results, the composite joint reinforcement is mainly attributed to ...
#1Maoqing Fu(HIT: Harbin Institute of Technology)H-Index: 4
#2Guodong Fang(HIT: Harbin Institute of Technology)H-Index: 15
Last. Jun Liang(BIT: Beijing Institute of Technology)H-Index: 24
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Abstract Z-pinned/bonded hybrid joints are widely used in the 2D C/SiC composite structures, whose mechanical behavior and failure mechanisms are directly related with the structure integrity. The hybrid joints for 2D C/SiC composite structures are formed by depositing SiC into the gap of z-pinned joints. To evaluate the SiC bonding effect, the tensile experiments for two kinds of z-pinned joints with and without bonded layer were conducted. It was proved that the failure modes of the pin were t...
Last. Francesco Vivio(University of Rome Tor Vergata)H-Index: 14
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Abstract The new Composite Bolted Joint Element (CBJE) is applied to the FE analysis of a single-lap, single-bolt composite bolted joint, allowing for important reductions of the computational burden while maintaining remarkable accuracy of results. The CBJE is a user-defined finite element representative of the elastic behavior of the region comprising the bolted joint and a portion of the surrounding composite plates. This modeling approach exploits radially disposed beam-shaped elements whose...