Hundreds of Takata inflators rupture during lab analysis
Hundreds of Takata airbag inflators ruptured in lab tests as researchers attempted to understand the root cause.
The National Highway Traffic Safety Administration recently published results from three in-depth investigations performed by different research firms. The teams analyzed data from Takata’s ballistic tests, which logged at least 660 failures out of 245,000 components pulled from vehicles in the field.
The risk at first appears to be low — only 0.27% of the field samples ruptured — but a closer look at the regional data suggests the potential for failure may be more than 30 times higher in certain areas that frequently experience high absolute humidity.
Statistical analysis performed by Orbital ATK attempted to understand a ‘striking’ difference in failure rates between individual counties in Florida, despite generally similar environmental conditions. Broward County was the highest with an 8.5 percent failure rate for a specific ‘PSPI-L’ passenger-side airbag inflator. Miami-Dade wasn’t far behind with an 8.3 percent rupture rate.
Broward and Miami-Dade are the most populous counties in Florida with more than 4.5 million residents combined.
The reports all confirm the early theory that Takata’s ammonium-nitrate propellant was sensitive to degradation via moisture exposure over time. Moisture appears to have transitioned in and out of propellant grains during thermal cycling, eventually creating porosity and fissures in the substance. Upon ignition, the increased surface area accelerates combustion and causes a pressure spike that can exceed the limits of the inflator chamber.
Researchers are still attempting to determine why certain vehicles, even two models built upon on the same platform, sometimes experience significantly different failure rates.
The symbiosis of time and regional environmental conditions has led to an unprecedented and controversial repair prioritization strategy supported by the National Highway Traffic Safety Administration. To hasten repairs for the oldest vehicles in the highest-risk zones, the agency has allowed automakers to continue installing potentially hazardous inflators in new vehicles.
Regulators have also received a petition from General Motors to delay repairs on certain 2007-2012 models. The company believes the data does not show the same elevated safety risk as other vehicles in the broader campaign.
“A primary question is whether the newer inflator designs are susceptible to failure under conditions that have resulted in [energetic disassembly] events with inflators currently under recall,” Orbital ATK concluded.
Takata’s own inquiry, led by German research firm Fraunhofer ICT, suggests the inflator industry lacks standard effective methods for validation and ongoing quality control.
“Takata continues to evaluate the performance of later generations of [phase-stabilized ammonium nitrate] products and will continue to cooperate with the OEM’s and government authorities in the resolution of this unfortunate issue,” the company wrote.