Fiber reinforced composites (FRC) are an adequate substitute for conventional materials. They are mainly used in aviation, the automotive industry and shipbuilding. In view of their heterogeneous structure, it is necessary to establish advanced experimental methods that allow a reliable estimation of the material response induced by the imposed mechanical loading history. Computed tomography (CT) is one of the most commonly used modern methods for non-destructive testing of composite materials. The proposed method allows the identification of localized fiber-matrix interactions in the bulk of the investigated test sample, as well as the adhesion properties of the connection between the constituents. With this full-field acquisition method it is possible to perform ex-situ and in-situ mechanical tests inside the CT scanner. Considering the ex-situ test protocol, the test sample is loaded outside the CT device and then scanned in the unloaded stage. However, the in-situ investigation of the material behavior, comprises the simultaneous scanning and loading of the test sample. Although in-situ tests have proven to be more comprehensive than ex-situ, they are more complex and require the use of specific loading devices that fit dimensionally inside a particular CT scanner without interfering with the scanning process of the specimen. In this thesis a quasi-static loading device is designed. The latter will allow an in-situ investigation of glass fiber reinforced composites. The device is adapted for three types of tomographs from different manufacturers: NIKON XT H 225, Werth S and NorthStar X50+. Based on the functional decomposition, morphological matrix and design requirements and constraints, several concepts have been proposed. By upgrading and improving all the aforementioned concepts, the final design of the in-situ loading machine was created. Furthermore, the adopted design was fully elaborated. All critical components of the loading machine were analysed via analytical calculations and numerical simulations. The developed device has a capacity of 5 kN, with the possibility to impose unidirectional and fully reversed cyclic tensile and compression loading histories. In addition, the modular design of the proposed device allows the investigation of test specimens of different thickness.