There is a growing interest for materials able to withstand increasingly more challenging conditions, such as temperatures above 2000°C, corrosive atmospheres, and combinations of mechanical stresses that are beyond the capabilities of current materials based on C/C or C/SiC composites. To tackle this challenge, a new class of materials based on ultra-high temperature ceramics reinforced with carbon fibres has been developed, tested and validated for use in extreme environments in the framework of the Horizon 2020 project C³HARME, demonstrating the capability of these new composites to provide both oxidation and mechanical resistance at high temperatures with negligible erosion. However, the specific weight of the final material is still relatively high compared to C/C composites (3.5 g/cm³ vs 1.8 g/cm³), so graded structures are currently being investigated to minimize the material’s density while retaining high mechanical strength in the core and corrosion resistance on the outer layers. In this work, two graded structures have been investigated: an inner core of ZrB₂/SiC rich in SiC, and an outer shell of either HfB₂ or MoSi₂, reinforced with long carbon fibres. From microstructural studies, the two different compositions were perfectly joined without any spallation or cracks. Preliminary oxidation resistance tests at 1650°C in air showed an improvement in oxidation behaviour over a baseline ZrB₂/SiC composite, while achieving lower specific weight. Further tests in an arc-jet facility were carried out to  study the high temperature resistance of these new graded structures, achieving promising results in terms of erosion and proving how graded structures are the next step for the improvement of these novel materials.