| Abstract: | ![]()
Pull-out experiments have been carried out with Kevlar fibres embedded in epoxy resin. Friction accompanied debonding, and had to be allowed for in the analysis. The debonding stress was about equal to the matrix strength for 80°C cured epoxies. However, debonding appears to be a brittle fracture process, and the works of fracture corresponding to the apparent interface strengths are very low, ranging from ca. 20-40 Jm-2 depending on the surface treatment and degree of cure of the resin. Water immersion for 2300 h at room temperature reduced the apparent strengths and works of fracture with some of the surface treated fibres, but not with the untreated fibres. Interface pressures during debonding were 10-15 MPa for the 20°C cured specimens and 20-30 MPa for the 80°C cure. Water soaking markedly reduced the friction coefficients. Post-debonding friction was high, but estimates of the parameters was probably unreliable due to the fibre having a somewhat thick end due to fibrillation when being cut. |
