Composite Materials

· The stress for fiber pull-out can be measured as illustrated.
· For a fiber of radius, r, and fracture stress, σ_f^* , the fiber will fail once the fiber stress reaches its fracture value.
· The length L_c, the critical transfer length, is required for the interfacial shear stress to load the fiber to its fracture stress. Fibers with a shorter length than this embedded in the matrix will pull out.
· The work done in pulling out a critical transfer length of fiber is:
W = (πr² /2) σ_f^* L_c .

From: Hull,
"Introduction to Composite Materials,"
Cambridge (1992)