The NASA Engineering and Safety Center (NESC) recently conducted a study to analyze the impact of abnormal grain growth (AGG) in the metallic liner of a composite overwrapped pressure vessel (COPV). This investigation focused on examining the mechanical behavior of the liner material, including the strain amplification factor (SAF), by using specially designed test pieces that combined metal and composite overwrap. The research indicated that this method was effective in assessing strain localization under different conditions and showed a strong correlation with modeling outcomes. Furthermore, initial tests of phase coherence imaging (PCI), an ultrasonic technique, showed promise in detecting AGG microstructures, although further refinement is necessary.
For more details, you can download the full report from NASA: [Effects of Large Grain Size in Composite Overwrapped Pressure Vessel](https://www.nasa.gov/wp-content/uploads/2026/02/tb-26-02.pdf?emrc=50ac99)
Original Source: NASA