THE PROCESSING, STRUCTURE AND PROPERTIES OF STRUCTURAL COMPOSITES FORMED BY REACTION INJECTION-MOLDING (SRIM)

Structural composites comprising an isocyanurate-modified polyurea (PU rI) matrix and pre-placed mats of continuous-fibres were produced in c ycle times of < 60 s via reaction injection moulding. The morphology a nd properties of the PUrI matrix were characterised using the SAXS, TE M, DMTA and tensile stress-strain techniques. Various hybrid SRIM comp osites with fibre contents up to 40% by volume were produced with sing le outer plies of unidirectional-fibre mats of either glass, carbon or Kevlar, and different numbers of inner plies of random glass-fibre ma ts. At a given volume fraction, tensile property data showed the modul us and ultimate elongation, parallel to the unidirectional fibre axes, to be determined mainly by the outer plies and to vary with fibre typ e, whereas the tensile strength varied only slightly. All of the tensi le properties perpendicular to the unidirectional fibre axes were esse ntially independent of the outer plies and were determined by the inne r random-fibre plies and the matrix. SEN fracture data were analysed u sing fracture mechanics to give K-IC and G(IC). As expected, values of K-IC and G(IC) parallel to the unidirectional fibre axes were greater than thounidirectional fibre axes were greater than those perpendicul ar, and were greater for composites comprising outer plies of unidirec tional glass rather than carbon.