Studies were conducted to address three specific questions related to the use of composite-reinforced pressure vessel designs for the transportation of compressed hydrogen at pressures up to 103 MPa (15,000 psi). These studies involved determining the hydrogen embrittlement resistance of AA6061-T6 aluminum alloy material typically used as a liner in composite-reinforced cylinder designs; determining whether composite-reinforced pressure vessels using plastic or thin-wall metallic liners were subject to distortion during the filament winding process; and identifying test methods that can be used to establish the long-term performance of non-metallic materials exposed to high-pressure hydrogen environments