OICC Press Journal of Nanostructure in Chemistry 2193-8865 16 5 2026 10 31 A Hygrothermal Plate Theory with Intrinsic Transverse Normal Strain for Predicting Interlaminar Stresses Accurately in Functionally Graded Graphene Nanoplatelet Composite Plates 10.57647/jnsc.2026.1605.23 EN Rui Ma College of Mechanical Engineering, Quzhou University, Quzhou 324000, China; Zhejiang Key Laboratory of Intelligent Manufacturing for Aerodynamic Equipment，College of Mechanical Engineering, Quzhou University, Quzhou 324000, Zhejiang, China 3 Yuan Hu Department of Aerospace and Mechanical Engineering, South East Technological University, Carlow, Ireland Hongliang Li Zhongzhe High-Speed Railway Bearing Co., Ltd. No. 33 Yongtai Road, Longyou Economic Development Zone, Quzhou 324400, China Fanzeng Guo Department of Aeronautics, Imperial College London, South Kensington Campus, City and Guilds Building, Exhibition Road, SW7 2AZ, London, UK Mingran Zhang College of Mechanical Engineering, Quzhou University, Quzhou 324000, China Abdul Ghaffar College of Mechanical Engineering, Quzhou University, Quzhou 324000, China Sadam Hussain College of Mechanical Engineering, Quzhou University, Quzhou 324000, China Manyu Zhang College of Mechanical Engineering, Quzhou University, Quzhou 324000, China Qilin Jin School of Engineering, Hangzhou City University, Hangzhou 310015, China https://orcid.org/0000-0003-3608-4819 Journal Article 2026 10 31 Graphene based nanocomposites have great mechanical properties which could be applied in multifunctional engineering. But it is also true that classical higher order theory cannot provide a good description of the interlaminar mechanical behavior of FG-GNPRC laminate under moisture and thermal condition. It's a big difference because of the different parts in hygrothermal expansion coefficient causing dissimilar elasticity so there will be very complicated stress distribution. We have then developed another modified plate formulation with moisture and temperature induced strain taken up by the definition of displacement field, which means it is incorporated into the kinematic description so as not to add any further unknowns to our model. The proposed model can have an exact interlaminar shear stress because there are no breaks between layer and temperature-humidity. Also, the removal of the curvature-related terms of in- plane displacements from shear stress expression simplifies the finite element implementation. It’s verified by comparison to 3D elasticity solutions and a few other classical theoretical models, which all show good agreement with the interlaminar stresses and deformations characterized here: And the parametric analysis shows more clearly what is governing the hygrothermal response. As we increase the GNP with some value and transverse deformations become large for having greater hygrothermal extension difference between low volumes but this is not true when increasing concentrations go on up to more amount. When we get quite different variation in GNP graduation across width that alters how stresses will behave from layer to layer, stress too by heat and water besides deformation and evolution of stress also depends on geometry proportion, stack configuration, applied load. All in all, they give structural response. These results can help in choosing suitable material gradation and structural design to improve the hygrothermal behavior of FG-GNPRC plates.