A study of the mechanical properties of liquid crystal polymer fibres and their adhesion to epoxy resin using laser Raman spectroscopy.
A number of high performance fibres (aramid, PBZT and PBO) spun from liquid
crystal polymer solutions were examined in this work. In particular, a thorough
investigation of the mechanical response of these fibres under tensile and
compressive deformations was carried out. The major experimental tool
employed was the technique of Laser Raman Spectroscopy. It was found that
stress-induced changes of these fibres at molecular level are proportional to the
macroscopic deformation applied. This correlation is unique for the fibres. A
method for converting spectroscopic data to predicted stress-strain curves in
tension and compression was proposed. An estimation of their compressive
strength was derived and an understanding of the nature of their compressive
failure was discussed.
The adhesion of these fibres to epoxy resin was also investigated by monitoring
in situ the interfacial stresses developed along the interface/interphaseo f model
single fibre composite coupons. The strength of the interfacial bond was
measured. The effect of various parameters such as fibre modulus, fibre diameter
and fibre nature upon the interfacial strength of the various systems was
evaluated. The mechanisms of stress transfer along with the nature of interfacial
damage was examined accurately. It was found that the major parameter
controlling the above mechanisms was interfacial yielding in shear. A numerical
appoximation (using Finite Element Analysis) was employed in order to evaluate
the experimental results. Finally, general conclusions concerning the
performance of these fibres were drawn.