Influence of Dynamic Multiaxial Transverse Loading on Ultra High Molecular Weight Polyethylene (UHMWPE) Dyneema SK76 Single Fiber Failure

A novel methodology for testing microscale single ballistic fibers under transverse impact to induce multiaxial loading is proposed and demonstrated using micron-scale (~18-m diameter) Dyneema SK76. Fibers are directly gripped to load cells and directly impacted by varying cylindrical loading geometries: razor (~2 m) to sharp (20 m) to blunt (200 m) in a modified Hopkinson bar at velocities of 10 and 20 m/s corresponding to nominal strain rates of 40006300 s1. Compared to high-strain-rate uniaxial tensile loading, failure strain was reduced by 28 , 32 , and 58 for blunt, sharp, and razor indenters, respectively, at strain rates of 4000 s1. At strain rates of 6300 s1, reductions were 34 , 39 , and 61 for blunt, sharp, and razor indenters, respectively. Fiber failure surfaces indicate tensile-dominated failure under blunt loading, shear failure under razor loading, and mixed failure under sharp loading. Experiments are modeled in LS-DYNA using a user material model to incorporate nonlinear inelastic transverse compressive behavior. A failure criterion incorporating multiaxial loading effects is applied to predict fiber failure, showing good agreement to the experimental results.