The overall performance of accelerator magnets strongly relies on electrical and mechanical robustness of their components. With an increase of the energy, future particle accelerators will have to withstand integral doses of ionizing radiation of up to several tens of MGy. Initially developed for the components of the D1 separation dipole magnet, designed and manufactured by KEK and part of the HL-LHC Project, this study was enlarged to characterise a spectrum of Glass Fiber Reinforced Polymers and resins potentially interesting for superconducting magnets. As a collaboration between CERN, KEK and QST Takasaki, an irradiation campaign was held with gamma-ray doses going from 10 MGy to 100 MGy. This paper describes the different methodologies applied to perform mechanical and chemical tests, both at room and cryogenic temperatures on a wide range of materials and resins. The results and the analysis of these tests are presented with the goal to provide some guidance on the choice of specific material or resin in HEP applications.