Composite Materials

· The response of a composite to an alternating stress involves the response of both the fibers and the matrix, and their orientation with respect to the applied alternating stress.
· The diagram shows the uniaxial stress/strain behavior for fibers that are elastic to fracture, and a matrix that will plastically deform below the

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

fiber fracture stress. The tests were at constant strain-rate.
· Fatigue damage occurs in a material if the local stress is greater than the yield stress. For this system, fiber fatigue resistance should be good; the matrix will be susceptible to fatigue damage which will increase with increasing periodic stress or lower fiber volume fraction, V_f .