Browsing by Author "Lai, FM"

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Experimental and theoretical predictions of first-ply failure strength of laminated composite plates
(1999-06-01)
Kam, TY
;
Lai, FM
;
機械工程學系
;
Department of Mechanical Engineering
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. (C) 1999 Elsevier Science Ltd. All rights reserved.
Finite element analysis of foam-filled laminated composite sandwich plates
(1998)
Kam, TY
;
Lai, FM
;
機械工程學系
;
Department of Mechanical Engineering
A multi-layer plate element formulated on the basis of the layerwise lineal displacement theory is presented. The finite element together with an appropriate failure criterion are applied to the determination of stress distribution in and initial failure strength of foam-filled laminated composite sandwich plates. The accuracy of the present finite element in predicting stresses is verified by the existing solutions. Experimental results are used to verify the accuracy of the proposed method in failure load prediction. The effect of number of layer groups used in the finite element analysis and the suitability of the adopted failure criterion on first-ply failure strength prediction are investigated. The superiority of the present finite element over the first-ol der shear deformable (FOST) finite element on first-ply failure strength prediction is demonstrated via a comparative study.
Minimum weight design of laminated composite plates subject to strength constraint
(1996-08-01)
Kam, TY
;
Lai, FM
;
Liao, SC
;
交大名義發表
;
機械工程學系
The minimum weight of laminated composite plates subject to strength and side constraints is studied via a constrained global optimization technique. The first-ply failure load that is treated as the strength of a laminated plate is determined by using a shear deformable finite element and one of the several commonly used phenomenological failure criteria. The optimal layer group parameters (fiber angles and thicknesses of layer groups) of the laminated composite plate are determined Via the proposed constrained global optimization technique for attaining the global minimum weight of the plate and satisfying the imposed constraints. A number of examples of the minimum weight design of symmetrically laminated composite plates with various aspect ratios, different number of layer groups, and different boundary conditions are given to illustrate the applications of the present constrained global optimal design method. The effects of the failure criteria on the optimal design parameters are also investigated via the examples. Finally, experimental investigation of the capability of the present method in obtaining global optima is performed. Failure tests of a number of graphite/epoxy laminates designed by different methods are performed, and the superiority of the present method over the other methods is demonstrated via the test results.
Minimum weight design of laminated composite plates subject to strength constraint
(1996-08-01)
Kam, TY
;
Lai, FM
;
Liao, SC
;
機械工程學系
;
Department of Mechanical Engineering
The minimum weight of laminated composite plates subject to strength and side constraints is studied via a constrained global optimization technique. The first-ply failure load that is treated as the strength of a laminated plate is determined by using a shear deformable finite element and one of the several commonly used phenomenological failure criteria. The optimal layer group parameters (fiber angles and thicknesses of layer groups) of the laminated composite plate are determined Via the proposed constrained global optimization technique for attaining the global minimum weight of the plate and satisfying the imposed constraints. A number of examples of the minimum weight design of symmetrically laminated composite plates with various aspect ratios, different number of layer groups, and different boundary conditions are given to illustrate the applications of the present constrained global optimal design method. The effects of the failure criteria on the optimal design parameters are also investigated via the examples. Finally, experimental investigation of the capability of the present method in obtaining global optima is performed. Failure tests of a number of graphite/epoxy laminates designed by different methods are performed, and the superiority of the present method over the other methods is demonstrated via the test results.
Optimum design of laminated composite foam-filled sandwich plates subjected to strength constraint
(1999-07-01)
Kam, TY
;
Lai, FM
;
Chao, TM
;
機械工程學系
;
Department of Mechanical Engineering
Optimum design of laminated composite sandwich plates with both continuous (core thickness) and discrete (layer group fiber angles and thicknesses) design variables subjected to strength constraint is studied via a two-level optimization technique. The strength of a sandwich plate is determined in a failure analysis using the Tsai-Wu failure criterion and the finite element method which is formulated on the basis of the layerwise linear displacement theory. In the first level optimization of the design process, the discrete design variables are temporarily treated as continuous variables and the corresponding minimum weight of the sandwich plate is evaluated subject to the strength constraint using a constrained multi-start global optimization method. In the second level optimization, the optimal solution obtained in the first level optimization is used in the branch and bound method for solving a discrete optimization problem to determine the optimal design parameters and the final weight of the plate. Failure test of laminated composite foam-filled sandwich plates with different lamination arrangements are performed to validate the proposed optimal design method. A number of examples of the design of laminated composite foam-filled sandwich plates are given to demonstrate the feasibility and applications of the proposed method. (C) 1999 Elsevier Science Ltd. All rights reserved.