Composite Materials

· For short fiber composites, fatigue life depends on the fiber aspect ratio (L/d).
· The higher aspect ratios approximate continuous fiber behavior. Sample failure is due to interfacial fracture and matrix brittle rupture at 45⁰ to the fiber axis.
· Aspect ratios of 200 or larger give composite performance close to that of continuous fibers at the same V_f .
· The diagram shows the response of an

From: Hertzberg & Mason, Academic Press (1980)

aligned boron short-fiber epoxy matrix system for applied stresses shown as a percent of the static failure stress. The fatigue life is the number of cycles producing a 20% decrease in the elastic modulus and ranges from 10³ to 10⁶.