Researchers at Drexel University, in collaboration with Exxon Mobil, discovered that non-elastic simple fluids can fracture, a phenomenon previously thought to require elasticity.

Thamires Lima, a chemical engineering professor, observed a hydrocarbon blend crack under stress during an extensional rheology test. This brittle fracture, similar to that seen in glass, contradicted the understanding that viscosity only rearranges molecules. Arnold Mathijssen, a fluid physicist, noted this challenges the expectation that simple fluids should flow rather than break.

The Drexel team, led by Nicolas J. Alvarez, used high-speed cameras to confirm the brittle fracture. While complex fluids like polymer melts can fracture due to molecular entanglement, the hydrocarbon blend lacked significant elasticity. This observation revisits Daniel D. Joseph's 1990s theories suggesting that sufficient tearing stress, potentially related to cohesive energy or cavitation, could fracture any liquid.

Cracks in simple fluids propagated at 500 to 1,500 meters per second, significantly faster than in complex fluids. Both simple and complex fluids fractured at a critical stress of 2 megapascals. The team theorizes that the speed of fracture relates to the fluid's ability to dissipate energy. Future work may explore fracturing less viscous liquids like water with faster machinery.