STRESS DISTRIBUTIONS DURING FIBER PULL-OUT

Fiber pull-out resistance is an important mechanism of energy absorpti on during the failure of fiber-reinforced composite materials. This pa per deals with axial stress distribution in the fiber during a pull-ou t The frictional constraint between the fiber and the matrix is modele d with a perturbed Lagrangian approach and Coulomb's law of friction. Stress distribution has been determined for three cases, using the fin ite element method. The first case deals with the pull out of a fully embedded fiber. The second determines the stress distribution during f iber pull-out in the presence of a broken-embedded fiber. The third mo del attempts to solve the pull out of a coated fiber. The results for the first case compares favorably with those in existing literature. A local ''pinching'' effect, due to the matrix collapse behind the pull ed fiber, is brought out clearly by this model. The second study indic ates that the ''plug'' effect may not be significant in affecting the stress distribution, Lastly, the effects of coating stiffness and thic kness are investigated.