Compressive Strength Analysis for High Performance Fibers with Different Modulus in Tension and Compression

Abstract

The assumption of equal tensile and compressive modulus necessary to determine single fiber axial compressive strength from the elastica loop test is relaxed by deriving a compressive strength equation based on the analysis of the flexural response of a fiber with different modulus in tension and compression. Previously determined tensile (E1t) and compressive (E1c ) modulus values for different high performance organic fibers with varying degrees of lateral molecular interactions are used to determine fiber compressive strength. The importance of using the bi-moduli equation becomes evident in the case of fibers that lack strong intermolecular interactions, since calculations done with the original loop test equation can result in an overestimation of the compressive strength on the order of 80%, as seen for the poly-(p-phenylene benzobisoxazole) fiber PBO. Kink band angles measured from looped fiber specimens are documented and correlated to the calculated compressive strength values.

Dynamic modeling of Kevlar KM2 single fiber subjected to transverse impact

“…3 are plotted using the nodes on the top surface of the fiber. This is consistent with the general response for flexural waves in thin rods (Graff, Table 1 Transversely isotropic properties of Kevlar KM2 single fiber (Cheng et al, 2005), (Leal et al, 2009). 1975).…”

“…However, fiber bending is significant. For the case of R = 0.5 mm, the compressive stresses are higher than the measured axial compressive strength (0.68 GPa Leal et al, 2009) and this indicates compressive kinking of the fiber will occur before flexural tensile stress approaches the tensile strength at a later time. For the case of R = 2.0 mm, the fiber undergoes reverse bending with increasing time and both top and bottom fiber surfaces are predicted to undergo compressive kinking.…”

“…They also reported a significant 50% reduction in tensile strength for imperfectly compressed fibers due to misaligned grips. Single fiber axial compressive strength for different fibers including Kevlar KM2 (0.68 GPa) are reported in Leal et al (2009). In their study, they report that KM2 fibers loaded in flexure fail in compression through the formation of kink-bands that causes fibrillation of the fiber microstructure.…”

Prediction of creep strain in mineral wool slabs under compression

“…Consequently, it is very important to know how deformations (creep deformations) of stone wool products develop over time, i.e. how they deform over time under the same constant long-term loads (under fixed stress) which influence the enlarged deformability of structural elements of the material (Leal et al 2009;Gnip et al 2012b).…”

Thermal fatigue and hypothermal atomic oxygen exposure behavior of carbon nanotube wire

“…For example, a 1-yarn CNT wire (yarn) has a tenacity of 65 cN/tex, while a 30-yarn CNT wire has a much lower tenacity of 32 cN/tex [8]. This decrease in tenacity can be explained by a large difference in tensile/compressive modulus of the CNT yarns as seen in several textile yarns [9,10]. Tenacity is considered synonymous to ultimate tensile strength, but describes the strength of yarn in terms of linear density, and is commonly used in textiles.…”