Abstract:This paper introduces first the features of interfacial microstructures and failuremodes of polymer composites. The progress of experimental study on theinterfacial properties of particle-filled polymers and blended polymers, as well as the testing methods and results obtained for interfacial properties are reviewed.The testing methods from macro-tension to in-situ meso-tension arediscussed, as well as the analytical methods from fractured surface micrographs to strength andenergy calculation. The advantages and disadvantages of those methods are analyzedat different scales. Finally, it isindicated that the major difficulties for interfacial characterizationby tests are related to the apparatus performance and the advanced testing methods. In order to get reliableproperties of the interface, one should be able to design the interface easyto be characterized, and to invent new techniques of testing.