The defective energy of interface of composite with imperfect interface is defined in terms of the representation of strainenergy deduced by variational method.

Analysis of stress concentrations in cross-ply (hybrid) laminates taking into account interfacial damage;

Based upon both the existing results of stress concentration analysis and randomly enlarging critical-core theory,a statistical analysis of the ultimate tensile failure process in cross-ply(hybrid) laminates due to the interaction of the matrix cracking in 90 degree ply,interlaminated interfacial failure,fracture of some fibers in 0 degree layers and fiber/matrix interfacial damage was performed.

Based on the shear-lag theory, a layering shear-lag model taking into account the interfacial damage was proposed and the stress redistributions for notched cross-ply laminates under tension were analyzed, from which both the length of the interfacial damage area and stress concentration factors in intact fibers at root of the notch were obtained.

The prediction of overall average mechanical properties for multi-phase composites with imperfect interphase;

A cohesive zone model is employed to simulate the fiber/matrix interface damage of composites with ductile matrix.

The damage bounding surface concept is introduced to develop the modified four parameter Hsieh-Ting-Chen model.

The results show that the interfacial creep damage of undermatching welded joint is very ser.