Fatigue dimensioning of vehicles and on-board equipment

The major obstacles to the rapid democratisation of hydrogen through means of transport remain the additional costs of the vehicle when purchasing it, as well as of hydrogen when recharging. Batteries and hydrogen constitute two complementary technological bricks. Combined, they can cater for a wide variety of use by parameterising the battery capacity, the power of the fuel cell, and the capacity of the hydrogen tanks (possible architectures: range extender, mid-power, full power).

One of the key factors in the additional cost of the hydrogen vehicle is found in the hydrogen storage. In an effort to reduce weight, metal tanks (type I and type II) have given way to composite tanks.

The issue of fatigue dimensioning is important because it makes it possible to optimise the complete system to obtain the best compromise between weight reduction and reliability, while respecting existing criteria, or the requirements associated with the vehicle architecture.

The methodology developed by our teams integrates know-how in the field of fatigue characterisation and testing of materials, as well as knowledge of the mechanical and vibratory stresses applied to these systems.

These two aspects contribute to the optimisation of the simulations in order to ensure a test/computation correlation and to estimate the optimal lifetime of the system upstream of the testing.

• In-vehicle systems and components

During cyclic thermomechanical loading, Type III tanks are limited by the liner material. As for type IV tanks, their liners are less impacted by pressure, they are however subject to creep and to the polymer aging phenomenon.

• Support and retention brackets

The stresses these systems encounter must be known in order to perform the fatigue analysis. These are totally dependent on the choice of integration of the system into the vehicle architecture.