Papers by Keyword: Composite Laminate

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Authors: Yu Pu Ma, Xin Zhi Lin, Qing Fen Li, Zhen Li
Abstract: When stress is high, delaminate damage can be induced by transverse cracks. A complete parabolic shear-lag damage model containing delamination induced by transverse cracks is therefore proposed and applied to predict the stiffness reduction by transverse cracking in cross-ply laminated composite materials. The predictions of the complete parabolic shear-lag analysis model, the incomplete parabolic shear-lag analysis model, and the complete parabolic shear-lag damage model containing delamination proposed in this paper have been compared. Results show that the young’s modulus reduction values obtained by our analysis model are better agreement with the experimental ones than other models.
Authors: Zhong Hai Xu, Rong Guo Wang, Wen Bo Liu, Cheng Qin Dai, Lu Zhang, Xiao Dong He
Abstract: In this paper, we predict the delamination buckling behavior in slender laminated composite with embedded delamination under compressive load by using the finite element method (FEM). For the different delamination size and depth position, we illustrate the various parameters effects on buckling behavior.
Authors: Yu Liu, Zheng Li, Ke Zhuang Gong, Xian Yue Su
Abstract: This paper describes a quantitative damage identification method for CF/EP composite laminates based on Lamb waves excited by distributed PZT wafers. The fundamental symmetric mode S0 is considered to detect defects (hole) in the plate. The Morlet wavelet and the cross-correlation analysis are introduced as signal processing tools for determining the time-of-flight (ToF) of Lamb wave. Considering the difference of Lamb wave velocities in different directions in a composite plate, the relationship of Lamb wave velocity in a unidirectional fibre reinforced laminate is studied and validated experimentally and numerically. In addition, a defect identification approach is revealed based on a regular arrangement of PZT wafers. Then, on the basis of the relationship of the wave velocity and the ToF, the location of a hole is identified by proposed method. Results demonstrate that the method is feasible in quantitative diagnosis of composite structures.
Authors: Di Zhang, Xi Tao Zheng, Li Nan Cheng
Abstract: This paper mainly presents a method that can characterize the damage tolerance capability of composite laminates based on the knee-point feature. Based on the experimental study and numerical result, the Knee-point mechanism has been investigated. A new influence coefficient, δ, was introduced, which is applied to calculating the influence of every piles damage to the residual strength of the whole laminates. Finally, a conclusion can be drawn that the damage of 0° piles can represent the damage of the whole laminates, whilst the damage area of 0° piles can be applied to characterizing the damage tolerance capability of composite laminates.
Authors: Hao Chen, Xiao Yan Tong, Xiang Zheng, Lei Jiang Yao
Abstract: One of the problems preventing the industrial application of composites is the lack of an efficient method to detect and discriminate among types of damage occurring during service. To solve this problem, low velocity impact experiments are carried out on T300/QY8911 composite laminates. And synchronously, the acoustic emission (AE) technique and impact monitoring systems were used to record the AE signals and the impact force. The damage evolution, damage modes and acoustic emission (AE) activity were easily detected and evaluated by the analysis of both AE waveform and impact load. In this way, the damage development process containing matrix cracking, delamination and fibers breakage is investigated. The energy release of damage are theoretically approximated and correlated with the AE energy. By the theory, the “high energy damage zone” is defined in the scatter diagrams of amplitude-frequency. It is easily to prove that the primary damage mode of “high energy damage zone” is delamination.
Authors: M.A. Marques, J. Monteiro, Carlos A. Ramos, M.A. Vaz, António Torres Marques
Abstract: In this work the actuator performance of a ceramic piezoelectric device is studied. Its ability of deforming a Carbon Fiber Reinforced Plastic (CFRP) laminate is measured in the absence/presence of mechanical constraints. Deformation and bending of the CFRP laminate is obtained when a voltage is applied to the piezoelectric device. This deformation was assessed using ESPI technique and a very good agreement with the expected values for the unconstrained case was observed. When completely embedded a reduction of 86% in the piezoelectric response is expected. Finite Element Analysis confirmed the obtained experimental data and a very good linearity in the response was observed.
Authors: Hamid Sheikh, Liang Huang
Abstract: This paper presents an efficient finite element modeling technique for stiffened composite shells having different stiffening arrangements. The laminated shell skin is modeled with a triangular degenerated curved shell element having 3 corner nodes and 3 mid-side nodes. An efficient curved beam element compatible with the shell element is developed for the modeling of stiffeners which may have different lamination schemes. The formulation of the 3 nod degenerated beam element may be considered as one of the major contributions. The deformation of the beam element is completely defined in terms of the degrees of freedom of shell elements and it does not require any additional degrees of freedom. As the usual formulation of degenerated beam elements overestimates their torsional rigidity, a torsion correction factor is introduced for different lamination schemes. Numerical examples are solved by the proposed finite element technique to assess its performance.
Authors: Gong Dong Wang, Jun Wang, Hao Chen
Abstract: An improved Memetic algorithm is applied in this article. Mathematical model is proposed to optimize the laminate strength. The composites laminate strength optimization system with local operator library and rule operator library has been developed by the object-oriented programming with C++. The local operator has contributed to increase the convergence rate and the rule operators have contributed to implement practical design aspects in optimization of laminated composite plates. A numerical example demonstrates the validity of optimization model and practical applicability of the improved Memetic algorithm; hence, exhibiting the improvement of the method in tackling the stacking sequence.
Authors: N. Hamani, Djamel Ouinas, N. Benderdouche, Mohamed Sahnoun
Abstract: In this study, an analysis of buckling was carried out on composite rectangular plates with and without circular notch by using the finite element method. The graphite/epoxy laminated plates were arranged antisymmetrically in the following ordered way [(θ/-θ)2]s. The buckling strength of the asymmetrical laminated plates subjected to uniaxial load is determined as a function of fiber orientation. The results show that whatever the notch radius, the buckling load is almost stable. The cumulated effect due to the presence of the longitudinal and transverse cracks as well as a circular notch reduces the buckling load considerably, which increases the risk of the fracture.
Authors: Heung Soo Kim, Jae Hwan Kim, Seung Bok Choi
Abstract: A modal strain based damage index is proposed to investigate the damage effects of discrete delaminations in a laminated composite structure. The Fermi-Dirac distribution function is incorporated with an improved layerwise laminate theory to model smooth transition of the displacement and the strain fields at the delaminated interfaces. Modal analysis is conducted to investigate dynamic effects of delamination in a laminated structure and to obtain modal strains. The damage index is calculated based on fundamental modal strains of laminated structures. The damage effects of laminated structures are investigated using arbitrary size, number, location and boundary conditions of discrete delaminations.
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