Please cite this article in press as: D. Wang, et al., Streamline stiffener path optimization (SSPO) for embedded stiffener layout design of non-uniform curved grid-stiffened composite (NCGC) structures, Comput. Methods Appl. Mech. Engrg. (2018), https://doi.org/10.1016/j.cma.2018.09.013. Available online at www.sciencedirect.com ScienceDirect Comput. Methods Appl. Mech. Engrg. ( ) – www.elsevier.com/locate/cma Streamline stiffener path optimization (SSPO) for embedded stiffener layout design of non-uniform curved grid-stiffened composite (NCGC) structures Dan Wang a , ∗ , Mostafa M. Abdalla b , Zhen-Pei Wang c , Zhoucheng Su a a Institute of High Performance Computing (IHPC), Agency for Science, Technology and Research (A*STAR), 1 Fusionopolis Way, 138632, Singapore b Zewail City of Science and Technology, Sheikh Zayed District, 12588, Giza, Egypt c Department of Civil and Environmental Engineering, National University of Singapore, No.1 Engineering Drive 2, 117576, Singapore Received 15 May 2018; received in revised form 17 August 2018; accepted 6 September 2018 Available online xxxxx Highlights • Bio-inspired shallow stiffeners embedded inside the laminate skin is proposed. • Curved stiffener layout optimization is solved based on multiscale modeling. • Curved stiffener paths are interpreted using the streamline functions. • Parallelogram representative cell configurations provide analytical sensitivities. Abstract A bio-inspired concept of non-uniform curved grid-stiffened composite structures with embedded stiffeners (embedded NCGCs) is proposed in the paper. Shallow curved stiffeners are embedded in the laminate skin to form an integrated structure to improve the skin–stiffener deformation compatibility. A method named streamline stiffener path optimization (SSPO) based on multiscale modeling is proposed for curved stiffener layout design of embedded NCGCs. Firstly, the homogenization-based global/local analysis is used to calculate structural responses on a global unstiffened model with the equivalent material properties obtained from local representative cell configurations (RCCs). Secondly, the discrete distribution of 2D curved stiffener paths is transformed into a continuous distribution of the streamline function values (SFVs) on a 3D level set surface. The stiffener path description using the streamline function is similar as the level set method with specific constraints. Projections of points with the same integral SFVs will form one stiffener path. Thirdly, optimal curved stiffener layout is achieved using shape design of local parallelogram representative cell configurations with analytical sensitivities calculated using the affine mapping from the square master domain to the parallelogram RCCs. Fourthly, stiffener spacing and angle constraints are added for manufacturing considerations and local buckling resistance, and optimization design is implemented to maximize the buckling load within a given ∗ Corresponding author. E-mail address: wang dan@ihpc.a-star.edu.sg (D. Wang). https://doi.org/10.1016/j.cma.2018.09.013 0045-7825/ c ⃝ 2018 Elsevier B.V. All rights reserved.