Failure by Fiber Pullout

For L L, the fiber is estimated to fail when Oj = where is the ultimate 

For L the matrix bond will fail in shear when t = of the matrix, and the fiber will puU onL This will also occur when there is less than perfect bonding, and the fiber debonds and pulls out. Contrary to what we might initially presume, less-than-perfect bonding is desired for better impact strength. Use of short fibers, designed to slip and pull out, gives a better polymer for energy absorption in impact situations. See Chapter 5 for impact properties. 

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