Time Effect in Extensional Electrorheological Characterization

• Type: Article in International Conference Proceedings Book
• Date: 2020-08-21

Authors

Laura Campo-Deaño (Author) FEUP; Francisco Galindo-Rosales (Author) FEUP; Samir Sadek (Author) FEUP; Hossein Najafabadi (Author) Other

Conference proceedings International

Title: PROCEEDINGS OF THE IBERIAN MEETING ON RHEOLOGY (IBEREO 2019)

Pages: 152-156

7th Iberian Meeting on Rheology (IBEREO) of the Spanish-Group-of-Rheology (GER) and Portuguese-Society-of-Rheology (SPR)

Univ Porto, Porto, PORTUGAL, SEP 04-06, 2019

Indexing

ISI Web of Knowledge - 1 Citation

Other information

Authenticus ID: P-00T-YG6

DOI: 10.1007/978-3-030-27701-7_32

Abstract (EN): When performing extensional ER tests for the characterization of electro-rheological fluids, the time between applying the electric field and triggering the experiment (delay time) plays an important role in ER behaviour of the sample. The current study investigates the delay time effect in extensional ER characterization. The ER sample used in the measurements is a suspension of cornstarch in olive oil with a concentration of 30 wt%. Fixtures adaptable to the commercial version of the Capillary Breakup Extensional Rheometer (HaakeTM CaBERTM, Thermo Scientific) are designed and fabricated to allow the application of an external electric field aligned with the flow kinematics undergone by the fluid sample while the extensional characterization is taking place. An in-house code developed in Matlab is used to process the images and investigate the filament thinning behaviour of the sample under 3 kV applied voltage and at different delay times (0 s, 10 s, and 40 s). The results show that, under extensional flow, when the voltage is applied, and the delay time between setting the electric field and triggering the experiment is 10 s, the fluid filament breaks. However, if the delay time is increased up to 40 s, then it is observed that the filament does not break anymore. Thus, increasing the time between applying the voltage and triggering the experiment strengthens the structure of the ER sample. According to these results, it can be concluded that the formation of the microstructure due to the presence of the electric field does not occur instantaneously, but instead it is a time-dependent phenomenon.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 5