The NASA Engineering and Safety Center (NESC) performed an assessment to characterize the effects of abnormal grain growth (AGG) within a metallic liner of a composite overwrapped pressure vessel (COPV). This effort focused on evaluating the mechanical response of the liner material, including the strain amplification factor (SAF), using a series of custom-designed coupons that incorporated both metal and composite overwrap. The study demonstrated that this approach was effective and practical to characterize strain localization under various conditions and showed strong correlation with modeling results. Additionally, preliminary investigations of phase coherence imaging (PCI), an ultrasonic technique, offered promise in detecting AGG microstructures, but further development is needed.

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