The effect of fiber meso/nanostructure on the transverse compression response of ballistic fibers

The goal of this research is to understand the effect of fiber meso/nanostructure on the macroscopic quasi-static transverse compression response of ultra-high molecular weight polyethylene (UHMWPE) Dyneema SK76 fibers. These fibers exhibit nonlinear inelastic behavior with a small elastic limit and negligible elastic recovery upon unloading. Finite element model predictions of the experiment, using a continuum nonlinear inelastic constitutive description agree reasonably well with experimental force-displacement, but under-predict the contact area. The apparent fiber cross-sectional area is found to increase up to a maximum of 1.83 times the original area at 46% nominal strain. SEM and AFM images of the meso/nanostructure of the compressed fibers indicate the apparent area growth is due to fibrillation. This fibrillation results in the deformation of a fibril network causing non-uniform fibril nesting and nucleation of new nanoscale voids between fibrils. A comparison of UHMWPE and Kevlar KM2 fiber transverse compressive response is also discussed.