Composite Materials

· For the case where the fiber fails at a lower fracture strain than the matrix, the composite also shows two fracture modes as a function of V_f .
· For V_f < V_min , the matrix can carry the extra load and the composite is stable on fiber failure. Fibers reduce the matrix volume fraction and reduce the composite fracture strength so that: σ^*_C1 = σ^*_m V_m = σ^*_m(1 - V_f) .
· For V_f > V_min , the load transfer takes the matrix above its fracture stress and the composite fails: σ^*_C1 = σ^*_f V_f + σ_m (1 - V_f )

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