Damage Tolerance Estimation of Advanced Composite Materials

Abstract

Japanese industrial standard for interlaminar fracture toughness tests of carbon fiber composites will be established. In order to achieve the reliable and easy-to-use test environment according to the standard, a computer aided test (CAT) system has been developed in the present paper. DCB and ENF tests for Mode I and II delamination fracture, respectively, have been applied to determine the interlaminar fracture toughness at initiation and during propagation. A mechanical servo testing machine has been controlled by a personal computer through GP-IB interface. A quasi-multiwindow man-machine interface has been designed for easy operation. The ENF test has been carried out under crack shear displacement (CSD) control, and stable delamination growth has been achieved. Delamination length has been monitored from the load versus crack opening or shear displacement (COD or CSD) diagrams based on the modified compliance calibration method. The method is very important technique for instrumentation of the interlaminar fracture toughness tests. Onset of delamination and delamination growth resistance characteristics (R-curves) in Modes I and II can be obtained automatically under the controlled delamination growth with the CAT system. Two types of advanced toughened CFRP, AS4/PEEK and T800H/3900-2, have been tested by the developed CAT system, and applicability of the test system has been examined.