In the aerospace industry, there is a strong need for structures that combine high stiffness and strength with low mass. Truss structures represent promising candidates, as they are composed of slender members primarily subjected to tensile or compressive loads [1,2]. They are assembled into lattice arrangements with various joining techniques, such as welding or mechanical fastening. However, despite their potential, the mechanical characterization and modelling of architected composite structures assembled with screws remain scarcely addressed in the literature. In this work, we develop a finite-element framework for the mechanical sizing of periodic lattice–skin structures intended for aircraft wing applications. The lattice is composed of a thermoplastic matrix reinforced with continuous carbon fibers and assembled into octet-truss configurations using steel screws. A Python-based parametric beam-shell model is developed and used as input for mechanical simulations of large lattice–skin structures, enabling significantly reduced computational time. The global mechanical response is captured, including stiffness and buckling behavior, along with appropriate modeling strategies for screwed joints. Concurrently, a local material failure analysis is carried out, using a surrogate post-processing model, trained on three-dimensional simulations of individual lattice components under relevant loading conditions, which in turn enables the fine-scale reconstruction of local stress fields. We perform a parametric study on the competition between buckling and material failure, and the results are compared with the performance of classical aluminum stiffened panels of same dimensions. In addition, mechanical tests on lattice components and on complete architected structures are performed to validate the numerical predictions and determine the parameters for damage initiation and failure criteria. This work highlights the potential of architected composite lattice-skin structures as lightweight, damage-tolerant, and repairable solutions for future aerospace structures.