Vitrimers represent a class of polymers featuring dynamic covalent crosslinks that can undergo dynamic network rearrangements and hold a notable promise as recyclable thermosets with crack-healing capabilities. In particular, vitrimers with aromatic disulfide hardeners have emerged over the past few years. In these high-glass-transition polymers, the healing regime coincides with the onset of thermal degradation, posing a fundamental challenge for reconciling adequate network mobility with thermal degradation prevention. Therefore, the present study explores the repair capabilities of glass fiber-reinforced polymers (GFRP) with a vitrimer matrix to understand how the interplay of temperature, time, and pressure affects the repair. A transferable framework for estimating a favourable time-temperature regime for vitrimer healing is introduced, based on thermal degradation and dynamic bond-exchange kinetics. The suggested optimized conditions are applied to repair different GFRP samples subjected to quasistatic intralaminar crack opening, and the extent of apparent mechanical property recovery is used to assess the repair effectiveness. Pressurized reconsolidation is required to restore the microstructure and repair cracks. When applying the prescribed repair conditions to the specific damage in short-beam samples, remarkable stiffness and strength recovery ratios of 93 % and 80 %, respectively, are achieved. Conversely, deviations from the prescribed regime due to improper dwell temperatures and times considerably reduce the recovery ratios of mechanical properties, limiting them to their residual values. However, the double cantilever beam repair conducted within the favourable regime shows that repair effectiveness depends strongly on the fracture surface morphology, revealing inherent limitations in the repair capabilities of the investigated laminate system.

The development of liquid hydrogen storage systems is a key aspect to enable future clean air transportation. However, safety analysis research for such systems is still limited and is hindered by the limited experience with liquid hydrogen storage in aviation. This paper presents the outcomes of a preliminary safety assessment applied to this new type of storage system, accounting for the hazards of hydrogen. The methodology developed is based on hazard identification and frequency evaluation across all system features to identify the most critical safety concerns. Based on the safety assessment, a set of safety recommendations concerning different subsystems of the liquid hydrogen storage system is proposed, identifying hazard scopes and necessary mitigation actions across various system domains. The presented approach has been proven to be suitable for identifying essential liquid hydrogen hazards despite the novelty of the technology and for providing systematic design recommendations at a relatively early design stage.