NASA's Langley Research Center has developed a novel polymer material that can be utilized as a real-time structural health monitoring sensor. The material is electroactive and generates a signal in response to a mechanical force. The material is also highly elastic, which allows for a large range of measurable strain levels, and is highly durable.
The material is manufactured into micro- and/or nanofibers from poly-vinylidene fluoride (PVDF), a thermoplastic fluoropolymer that is highly piezoelectric when poled. The material can either be spun directly onto composite panels or can be embedded within the material. Defect detection is captured as the result of the piezoelectric PVDF fibers acting similarly to wires. The fabrication method of the electroactive material is based on a previous NASA Langley invention of an apparatus that is used to electrospin highly aligned polymer fiber material.
Voltage output is potentially ten times stronger than PZT (lead zirconate titanate), a commonly used piezoelectric sensor. The material is highly durable, except for high levels of gamma radiation. PVDF fibers have no foreseen limits in length and size, and fiber diameter is tailorable. In addition, the cost of real estate and equipment required to produce the material is low. Potential applications include impact, delamination, and fatigue crack sensing.