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R R Chang - One of the best experts on this subject based on the ideXlab platform.

  • experimental and theoretical analyses of First Ply Failure of laminated composite pressure vessels
    Composite Structures, 2000
    Co-Authors: R R Chang
    Abstract:

    Abstract Experimental and analytical approaches are studied via the First-Ply Failure strength on symmetrically laminated composite pressure vessels with various material properties, radius-to-thickness ratios, and different numbers of layers subjected to uniform internal pressure loads. Optimal angle-Ply orientations of generally laminated symmetric [θ/−θ/…] S shells designed for maximum stiffness were investigated. A hand lay-up technique was used to laminate composite pressure vessels by the stacking of pieces of prepreg in the desired orientations and subsequent curing. The First-Ply Failure pressure loads of the laminated composite pressure vessels are determined using the acoustic emission AMS3 (AE) system. The experimental results have been proved to be efficient and effective in the theoretical prediction of First-Ply Failure strengths of laminated composite pressure vessels.

  • Predictions of deflection and First-Ply Failure load of thin laminated composite plates via the finite element approach
    International Journal of Solids and Structures, 1996
    Co-Authors: Tai-yan Kam, H. F. Sher, T.n. Chao, R R Chang
    Abstract:

    Abstract A nonlinear finite element method, which is based on the von Karman-Mindlin plate theory and the principle of minimum total potential energy, is used to study the deformation and First-Ply Failure of thin laminated composite plates. The load displacement curves of a number of laminated composite plates are determined using the proposed finite element method. Stresses obtained fr'om the linear and nonlinear finite element analyses are used to determine, respectively, the linear and nonlinear First-Ply Failure loads of the laminated plates based on several phenomenological Failure criteria. The accuracy of the finite element results is then verified by comparison with the available experimental data. It has been found that good agreement between the finite element and experimental load strain curves before First-Ply Failure is observed. If the reduction in plate stiffness induced by Failure of plies is taken into account in the finite element model, close agreement between finite element and experimental load displacement curves from First-Ply Failure up to total Failure may be obtained. Regarding the prediction of the First-Ply Failure load, it has been found that some of the phenomenological Failure criteria may yield results of consistent accuracy for the laminated composite plates under consideration. Nevertheless, accurate prediction of the Failure process after First-Ply Failure is still intractable. Hence, for reliability assurance further research on Failure analysis of laminated composite plates subject to transverse loading is needed.

Tai-yan Kam - One of the best experts on this subject based on the ideXlab platform.

  • Failure analysis of small composite sandwich turbine blade subjected to extreme wind load
    Procedia Engineering, 2011
    Co-Authors: C P Chen, Tai-yan Kam
    Abstract:

    Abstract In this paper, the progressive Failure process of composite sandwich wind turbine blades subjected to wind load is studied via both theoretical and experimental approaches. In the theoretical study, the wind pressure acted on the wind blade surface is estimated in an aerodynamic analysis. The stresses in the wind blade are determined using the finite element code ANSYS in which the skin and the core of the blade are modeled using shell and solid elements, respectively. A phenomenological Failure criterion is adopted to predict the First-Ply Failure strength of the blade. After the occurrence of the initial Failure, the material properties at the Failure locations are modified following a material degradation rule. The updated stiffness matrix of the blade is then obtained with the consideration of the changes of the material properties and configuration of the blade. An incremental load approach together with a sequential stiffness adjustment technique is used to trace the load-displacement curve and thus determine the ultimate strength of the blade. In the experimental investigation, a composite sandwich wind blade was fabricated for strength testing. In the test, the Whiffle-tree approach was used to simulate the wind load on the blade. The measured ultimate load of the wind blade was then used to validate the accuracy of the proposed method for Failure analysis of composite sandwich wind blades.

  • Experimental and theoretical predictions of First-Ply Failure strength of laminated composite plates
    International Journal of Solids and Structures, 1999
    Co-Authors: Tai-yan Kam, Feng-min Lai
    Abstract:

    Abstract Experimental and theoretical methods are presented to study the First-Ply Failure strength of laminated composite plates under different loading conditions. An acoustic emission technique is used to measure the energy released in the plates during the Failure process. The First-Ply Failure strength of the plates is then identified via the energy vs load diagrams which are constructed on the basis of the measured acoustic emissions. A finite element analysis, which is constructed on the basis of the layerwise linear displacement theory, and the Tsai–Wu Failure criterion are used to predict the First-Ply Failure strength of the plates. The comparison between the experimental and theoretical results shows good agreement.

  • First-Ply Failure strength of laminated composite pressure vessels
    Composite Structures, 1997
    Co-Authors: Tai-yan Kam, Y.w. Liu, F.t. Lee
    Abstract:

    Strengths of laminated composite pressure vessels are studied via both analytical and experimental approaches. Experimental techniques are presented to determine the First-Ply Failure and burst strengths of laminated composite pressure vessels with different lamination arrangements. Different analytical methods, together with various Failure criteria, are used to predict the First-Ply Failure strengths of the laminated pressure vessels. The accuracy of the theoretical prediction of First-Ply Failure strength is verified by the test data. The suitability of the Failure criteria, as well as the limitations of the analytical methods are discussed.

  • Predictions of deflection and First-Ply Failure load of thin laminated composite plates via the finite element approach
    International Journal of Solids and Structures, 1996
    Co-Authors: Tai-yan Kam, H. F. Sher, T.n. Chao, R R Chang
    Abstract:

    Abstract A nonlinear finite element method, which is based on the von Karman-Mindlin plate theory and the principle of minimum total potential energy, is used to study the deformation and First-Ply Failure of thin laminated composite plates. The load displacement curves of a number of laminated composite plates are determined using the proposed finite element method. Stresses obtained fr'om the linear and nonlinear finite element analyses are used to determine, respectively, the linear and nonlinear First-Ply Failure loads of the laminated plates based on several phenomenological Failure criteria. The accuracy of the finite element results is then verified by comparison with the available experimental data. It has been found that good agreement between the finite element and experimental load strain curves before First-Ply Failure is observed. If the reduction in plate stiffness induced by Failure of plies is taken into account in the finite element model, close agreement between finite element and experimental load displacement curves from First-Ply Failure up to total Failure may be obtained. Regarding the prediction of the First-Ply Failure load, it has been found that some of the phenomenological Failure criteria may yield results of consistent accuracy for the laminated composite plates under consideration. Nevertheless, accurate prediction of the Failure process after First-Ply Failure is still intractable. Hence, for reliability assurance further research on Failure analysis of laminated composite plates subject to transverse loading is needed.

P P Camanho - One of the best experts on this subject based on the ideXlab platform.

  • matrix cracking and delamination in laminated composites part i Ply constitutive law First Ply Failure and onset of delamination
    Mechanics of Materials, 2011
    Co-Authors: P Maimi, Joan A. Mayugo, P P Camanho, Albert Turon
    Abstract:

    Abstract Matrix cracking and delamination are the main initial forms of damage in advanced laminated composites manufactured by stacking unidirectional plies of fiber reinforced polymers. In this paper, the onset of matrix cracking is determined for in-plane stress states; in addition, delamination promoted by matrix cracks is analyzed. Taking into account that under in-plane shear stresses composite laminates show a non-linear response prior to the formation of a macro-crack, a plastic-damage model is proposed and implemented. The models predictions correlate well with published experimental data.

  • tailoring for strength of composite steered fibre panels with cutouts
    Composites Part A-applied Science and Manufacturing, 2010
    Co-Authors: C S Lopes, Zafer Gurdal, P P Camanho
    Abstract:

    A large number of composite parts include cutouts to accommodate windows, doors, and bolted joints. These regions are hot-spots in terms of design because they concentrate stresses, hence becoming critical in terms of the structural integrity of the part. A traditional approach to the problem of stress concentrations around cutouts is to locally increase the laminate thickness in order to improve the strength margins. Often this practice attracts more loads to the cutout besides increasing part weight. A more effective solution is to tailor the panel in-plane stiffness by means of fibre-steered laminates, and avoid the stress concentrations altogether. The present research demonstrates that it is possible to design and manufacture composite panels whose buckling and First-Ply Failure responses are insensitive to the existence of a central hole. Moreover, it is shown that the structural performance of these designs more than doubles that of straight-fibre configurations.

  • variable stiffness composite panels buckling and First Ply Failure improvements over straight fibre laminates
    Computers & Structures, 2008
    Co-Authors: C S Lopes, Zafer Gurdal, P P Camanho
    Abstract:

    One of the primary advantages of using fibre-reinforced laminated composites in structural design is the ability to change the stiffness and strength properties of the laminate by designing the laminate stacking sequence in order to improve its performance. This procedure is typically referred to as laminate tailoring. Traditionally, tailoring is done by keeping the fibre orientation angle within each layer constant throughout a structural component. Allowing the fibres to follow curvilinear paths within the plane of the laminates constitutes an advanced tailoring option that can lead to modification of load paths within the laminate to result in more favourable stress distributions and improve the laminate performance. Based on numerical simulations, the present work demonstrates the advantages of variable-stiffness over straight-fibre laminates in terms of compressive buckling and First-Ply Failure. A physically based set of Failure criteria, able to predict the various modes of Failure of a composite laminated structure, is implemented in finite element models of straight and variable-stiffness panels under compression. Non-linear analyses are carried out to simulate First-Ply Failure in the postbuckling regime.

F.t. Lee - One of the best experts on this subject based on the ideXlab platform.

  • First-Ply Failure strength of laminated composite pressure vessels
    Composite Structures, 1997
    Co-Authors: Tai-yan Kam, Y.w. Liu, F.t. Lee
    Abstract:

    Strengths of laminated composite pressure vessels are studied via both analytical and experimental approaches. Experimental techniques are presented to determine the First-Ply Failure and burst strengths of laminated composite pressure vessels with different lamination arrangements. Different analytical methods, together with various Failure criteria, are used to predict the First-Ply Failure strengths of the laminated pressure vessels. The accuracy of the theoretical prediction of First-Ply Failure strength is verified by the test data. The suitability of the Failure criteria, as well as the limitations of the analytical methods are discussed.

Roham Rafiee - One of the best experts on this subject based on the ideXlab platform.

  • stochastic prediction of burst pressure in composite pressure vessels
    Composite Structures, 2018
    Co-Authors: Roham Rafiee, Mohammad Ali Torabi
    Abstract:

    Abstract The main objective of this research is to predict burst pressure of composite pressure vessels subjected to internal pressure taking into account manufacturing uncertainties. Firstly, First-Ply-Failure (FPF) of composite pressure vessels with/without liner is studied comparing performance of different Failure criteria. Then, burst pressure of the vessels are deterministically predicted using progressive damage modeling based on continuum damage mechanics approach. Both theoretical modeling approaches on predicting FPF and burst pressure are validated using available experimental data. Finally, stochastic modeling is conducted to estimate burst pressure of composite pressure vessels taking into account fiber volume fraction, winding angle and mechanical and strength properties as random parameters resembling manufacturing-induced inconsistencies. Statistical data analysis shows the importance of taking into consideration manufacturing variability.

  • simulation of functional Failure in grp mortar pipes
    Composite Structures, 2014
    Co-Authors: Roham Rafiee, Farshid Reshadi
    Abstract:

    Abstract The main objective of this article is to simulate and analyze the functional Failure in composite pipes subjected to internal hydrostatic pressure. A progressive damage modeling is developed taking into account the influence of core layer incorporated in order to increase the pipe stiffness. The modeling procedure consists of four parts as model preparation, stress analysis, Failure evaluation and degradation rules. The developed modeling is validated using experimental results of a composite pipes consisting of FRP and sand layers. The influence of two main parameters as core thickness and the winding angles of cross plies are investigated. It is observed that First-Ply-Failure (FPF) and Functional Failure (FF) pressures increase linearly with increasing the core thickness; however the relative difference between FPF and FF pressures decreases. Three types of boundary conditions imposed from most common experimental setups are also simulated and analyzed. The variations of FF versus winding angles are investigated for all three sets of boundary conditions.

  • modeling and experimental evaluation of functional Failure pressures in glass fiber reinforced polyester pipes
    Materials & Design, 2014
    Co-Authors: Roham Rafiee, Ali Amini
    Abstract:

    Abstract The main objective of this paper is to predict the functional Failure pressure of Glass fiber Reinforced Polyester (GRP) pipes subjected to hydrostatic internal pressure. A progressive modeling procedure is developed to predict the internal pressure associated with weepage. The developed modeling consists of stress analysis, Failure evaluation and material degradation. The influence of micromechanics rules for estimating mechanical properties of constructing layers and Failure criteria for predicting Failure occurrence are examined in comparison with experimental observations and the best combinations of them are identified. First-Ply Failure and functional Failure pressures are determined and compared. A parametric study is conducted investigating the effect of fiber volume fractions and winding angles on the Failure pressures. The study is performed on five different volume fractions of 52.5%, 55%, 57.5% and 60% and three different winding angles of 52.5°, 57.5° and 60.19°. The results show that the functional and First-Ply Failure pressures decrease by increasing fiber volume fractions; while the higher winding angles (measured from the axial axis of pipe) enhance functional Failure pressures.