When an interface debonding occurs in a composite

The load level at which a debonding occurs on the constituent fiber/matrix interface of a composite subjected to any load is predicted. Only the original properties of the fiber and matrix measured from monolithic material specimens in addition to the transverse tensile strength of a unidirectional (UD) composite made from the same constituents are required. Stress concentration factors (SCFs) of the matrix in the composite are crucial for this purpose. Such an SCF cannot be defined following a classical approach. The SCFs with the perfect and debonded interfaces are derived, respectively. Letting the predicted transverse tensile strength of the UD composite with an initial perfect and later debonded interface be equal to the measured counterpart, a critical Mises stress of the matrix at which the debonding occurs is obtained. Each Mises stress of the matrix in any other composite from the same constituent system is assessed against the critical value, and the load level when the interface debonding occurs is determined accordingly.