Onboard Monitoring Method for Detection of Damage to Carbon Fiber Composite Overwrap on Hydrogen Fuel Tanks

Statement of the problem: Hydrogen fuel cell electric vehicles (FCEV) are attractive due to their lack of exhaust (they produce only heat and water), and the possibility of reducing our dependence on hydrocarbon fuels. One impediment to widespread adoption of hydrogen FCEV has been high production costs, driven in part by the need to over- engineer the carbon-fiber-overwrap-pressure vessels (COPV) which carry the compressed hydrogen fuel. Further, there is no way to continuously monitor the tank’s structural health mile after mile over the vehicle’s life. General statement of how this problem is being addressed: TDA Research has developed a structural health monitoring system that is lightweight, compact, and inexpensive. The system is entirely external to the tank and does not require any alteration of the composite tank; therefore, no requalification of the tank’s integrity is required. It has no moving parts and can be ruggedized to run on board vehicles. It can detect defect location, size and damage type. Most importantly this technology has the capability to predict when damage requires the tank to be replaced, before it becomes dangerous. TDA novel sensor technology can be used for non-destructive-evaluation (NDE) for inspection of composite tanks and structural carbon fiber composite in addition to COPV structural health monitoring system. Phase II progress: In the successful Phase II effort we demonstrated we can detect damage in full commercial COPV. The COPV were measured in two states; as received conditions (undamaged) and also after they were impacted with a calibrated weight. Our sensors showed that there was a clear damage profile in the location of and around the impact sites. We confirmed our sensor performance against X-Ray- CT provided by our collaborators at Lockheed Martin. We have designed and constructed two form factors – one sensor array for on tank monitoring and one automated gantry measurement for in lab QA/QC. Phase IIA plans: In the Phase IIA project we will continue our work developing an automated software to recognize damage to the COPV picked up by our sensor. We will expand our technique into Type IV COPV, and the larger COPV used by heavy duty vehicles (i.e. buses and long haul trucks). Commercial applications: Widespread adoption of hydrogen FCEV relies on a reduction in unit costs, some of which can be achieved by SHM of carbon fibers that provide the strength of the fuel cylinder. The technology also has wide application for NDE of composite used in the aerospace and defense industry.