PSI - Issue 70

Aamir Anwar Nezami et al. / Procedia Structural Integrity 70 (2025) 105–112

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laminates, CLPT begins converging at length to thickness ratio ( a/h ) of 50, whereas for eight-layer laminates, convergence occurs beyond a/h = 70 for anti-symmetric cross-ply while beyond a/h = 90 for anti-symmetric angle-ply laminate. 5. Conclusions This study presented a novel zigzag theory for analysing deformation, stress distribution, and buckling in laminated composites and sandwich plates. Hence this formulation works very well even for very thick and highly anisotropic multilayered laminated composite and sandwich plates. • It captures the warping of the plates (zigzag effects as observed in in-plane displacements) very accurately and maintains continuity of the transverse shear stresses at the interfaces of the laminated plates using constitutive relations and also satisfies zero shear stresses at the top and bottom surfaces of the plate. • This present theory is free from the flaws of the stiffening effect as observed when the number of layers increases in various other zigzag theories such as Tessler-RZT, Sorrenti-En-RZT, and Murakami Zigzag theory. • This enhancement of zigzag theory leads to having a fixed number of unknown variables while maintaining a good accuracy in thickness-wise distributions of in-plane displacements and stresses typically of a multilayered plate. • Murakami zigzag theory fails to give correct results in the case of a sandwich plate, while in laminated composite plates with all four stacking sequences, it gives results with the same accuracy as obtained from Sorrenti En-RZT. • Comparison of different theories reveals that Classical Laminated Plate Theory (CLPT) overestimates buckling loads for thick plates but provides satisfactory results for thin plates. • Hence this theory predicts stresses, strains and displacements at the laminae interfaces accurately such as to avoid the delamination of laminate. • The proposed higher-order zigzag theory is an important contribution to the composite plate mechanics field. The formulation’s accuracy with reduced computational complexity makes it a practical and powerful analytical tool for laminate and sandwich plate analysis. Abrate, S., Di Sciuva, M., 2017. Multilayer models for composite and sandwich structures. In: Elsevier eBooks, pp. 399 – 425. Pagano, N.J., 1970a. Exact solutions for rectangular bidirectional composites and sandwich plates. Journal of Composite Materials 4, 20 – 34. Di Sciuva, M., 1992. Multilayered anisotropic plate models with continuous interlaminar stresses. Composite Structures 22, 149 – 167. Tessler, A., Di Sciuva, M., Gherlone, M., 2009. Refined zigzag theory for laminated composite and sandwich plates. NASA Technical Report NASA/TM-2009-214053. National Aeronautics and Space Administration. Sorrenti, M., Di Sciuva, M., 2021. An enhancement of the warping shear functions of refined zigzag theory. Journal of Applied Mechanics 88. Sorrenti, M., Gherlone, M., 2023. A new mixed model based on the enhanced-refined zigzag theory for the analysis of thick multilayered composite plates. Composite Structures 311, 116787. Si, J., Chen, W., Yi, S., Yan, Y., 2023. A new and efficient zigzag theory for laminated composite plates. Composite Structures 322, 117356. Srinivas, S., Rao, A.K., 1970. Bending, vibration, and buckling of simply supported thick orthotropic rectangular plates and laminates. International Journal of Solids and Structures 6, 1463 – 1481. Jiarang, F., Jianqiao, Y., 1993. Exact solutions of buckling for simply supported thick laminates. Composite Structures 24, 23 – 28. Reddy, J.N., Phan, N.D., 1985. Stability and vibration of isotropic, orthotropic, and laminated plates according to a higher-order shear deformation theory. Journal of Sound and Vibration 98, 157 – 170. Murakami, H., 1986. Laminated composite plate theory with improved in-plane responses. Journal of Applied Mechanics 53, 661 – 666. References