<p>Carbon fiber reinforced sandwich materials are mostly used in industry to guarantee optimal price-performance ratios. Using these materials in bolted aeronautical parts requires the amelioration of their mechanical strength and their failure behavior. However, few studies have investigated the performances of sandwich-bolted assemblies destined for aerospace applications, especially under quasi-static and dynamic loadings. In this paper, an optimization study of a carbon fiber reinforced sandwich three-bolt, single-lap joint used in aircraft wing box is performed by considering that specific choices of material and dimensional properties of this joint afford ameliorated mechanical characteristics. For that, the results of experiments and non-linear numerical models developed in ANSYS software are exploited by the Taguchi method to determine the optimal design of the studied joint. Obtained results show that using a foam core with a good strength-to-weight ratio and composite skins with woven carbon fibers guarantees higher resistance against multidirectional loads. Also, the most critical failure mechanisms are skin/core debonding and cracking localized in the upper skin around the bolt that is close to the loaded side of the joint. For that, increasing the thickness of sandwich skins improves ultimate load, delays the initiation of cracks, and reduces PSD displacements. Furthermore, epoxy carbon woven skins and PMI205 foam core are chosen with specific thicknesses to obtain an optimized design of the sandwich element of the studied joint that shows an ameliorated ultimate strength and satisfying fatigue lifetime with 25% of weight saving compared to a standard bolted composite joint studied in the literature [<CitationRef CitationID="CR1">1</CitationRef>].</p> Graphical abstract <p></p>