Loading Rate Sensitivity of High Strength Fibers and Fiber/Matrix Interfaces

High strength fibers are extensively employed in many different composite applications. This article is concerned with the rate dependency of mechanical behavior of these fibers, namely S2 Glass (R), Kevlar 29 (R), and Spectra 900 (R) fibers at low loading rates. Also studied is bonding behavior of these fibers with the most used thermoset composite matrix materials, which are epoxy and polyester resins. With this regard, several tensile and single fiber pull-out tests were carried out by employing a 5 kN Instron testing machine. The experiments were conducted at loading rates ranging from 1 to 250 mm/min. Based on the results obtained in this research work, the tensile strength is increasing from 1 to 100 mm/min loading rate and fiber matrix bonding strengths are decreasing by enhancing loading rate. This implies that certain mechanical properties of some polymer matrix composites could be rate dependent, even at low loading rates.