Rate‐dependent mechanical response of polypropylene nonwovens.

Most nonwoven products are subjected to a variety of loading rates ranging from low‐speed quasi‐static loads to high‐speed dynamic loads during their life cycles. Understanding their response to a wide range of loading rates is critical to proper usage and effects how rapidly one can process them. In this work quasi‐static to high strain rate experiments (10−3 to 100 to 400 strain/s) are investigated. The results from analyzing the rate‐dependent properties show an increase in the strength and modulus accompanied by a reduced strain to failure in nonwovens as the strain rate increases. Higher basis weight samples showed more prominent rate‐dependent properties across all loading rates and fiber orientations. Ductile to brittle transition in the material failure mechanisms were observed. The specimens with rectangular and circular bonding patterns show higher strain localization than the specimens with the diamond bonding pattern due to the higher fiber reorientation. The rate dependent response at higher loading rates does not follow the typical rate dependent models of Johnson–Cook and Cowper–Symonds. This is a vital understanding as the material greatly stiffens up at higher rates and has a much lower strain to failure than one would expect. [ABSTRACT FROM AUTHOR]