Nanomodified Epoxies to Improve Fiber Strength in Overwrapped Pressure Vessels for Hydrogen Apps. S. Mondal
Use of Nanomodified Epoxies to improve fiber delivered strength in composite overwrapped pressure vessels for Hydrogen Storage Applications: A study was undertaken to investigate the effect of nanocalcite matrix modification on Composite Overwrapped Pressure Vessels (COPVs) for hydrogen gas storage. Thick-walled type III COPVs were prepared via filament winding using a conventional unfilled epoxy matrix as a control material and an epoxy matrix resin modified with surface-treated nanocalcite particles at 35% by weight (3M Developmental Resin AMD 931). The COPVs were evaluated for burst pressure. The results show that the modification of the filament winding matrix resin with nanocalcite significantly improved burst pressure relative to the unmodified control resin. Additionally, impregnated strand tensile strength testing was performed on Toray T700S carbon fiber to investigate the effect of matrix resin on realized fiber strength. Data from impregnated tow specimens made using 0 and 35 weight% nanocalcite in the epoxy show that nanocalcite modification shifts the delivered fiber strength (DFS) distribution. The higher performance demonstrated for a given design suggests that use of nanocalcite-modified matrix resin could enable improved margins of safety, qualification at increased burst pressure, or redesign to reduce COPV weight and cost. To examine the implications of the measured increase in hydroburst pressure on article design, a design optimization study based on finite element analysis (FEA) was performed for a nylon-liner 52L COPV design using the increased DFS values. The optimized tank having the same external envelope had overall weight reduction of 12% and increased gas-carrying volume of 12 % due to reduction in composite wall-thickness enabling increasing the internal volume. The impact of increased hydrogen tank capacity on fuel cell electric vehicle range will be discussed as well as additional design options that are enabled.