MEASURING THE ELASTIC PROPERTIES OF HIGH-MODULUS FIBERS

The measurement of the elastic constants of several highly oriented th ermoplastic polymer fibres is described. The method makes use of the h ot-compaction process, developed and patented in this laboratory, whic h enables a solid section of highly oriented polymer to be produced fr om an aggregate of highly oriented fibres. As only a small fraction of the original fibre is melted and recrystallized during the process, t he compacted materials offer a unique opportunity for measuring fibre properties in the bulk. An ultrasonic immersion technique is used to m easure the elastic properties of the compacted materials, from which t he properties of the polymer fibres are inferred. The experimentally d etermined fibre elastic properties have been compared with other orien ted polymer materials to assess any similarities in elastic anisotropy between different methods for producing fibre orientation, and compar ed with theoretical upper limits for the fibre elastic properties base d on theoretical estimates for the polymer crystal unit cell appropria tely averaged for hexagonal symmetry using the aggregate model.