Determination of Generalized Fracture Toughness in composite multimaterial closed corners with two singular terms – Part II: Experimental results

In this paper the experimental part of the procedure for the Generalized-Fracture-Toughness determination in multimaterial closed corners with two stress singularities is presented. The so-called Generalized-Fracture-Toughness (the critical values of the Generalized Stress Intensity Factors (GSIFs) at failure) can only be determined if each singular term can be isolated, after which the value of GSIF at the instant of failure can be evaluated. The loading configuration which allows the isolation of the stress singularities was analyzed in Part I, while the details of the testing procedure and postprocessing of the experimental results are covered in the present paper. The proposed test is a modified configuration of the Brazilian test in which the multimaterial corner tip is located at the center of the disk. A failure envelope based on the GSIFs and Generalized-Fracture-Toughness values at the corner tip is defined and proposed as a failure criterion for joints including this type of corners. Results for real adhesively bonded double-lap joints are presented showing a satisfactory agreement with the proposed failure criterion.

► A general procedure is presented for GSIF characterization at multimaterial corners. ► A novel modified configuration of the Brazil disk specimen is suggested. ► Particular numerical example is presented for a bimaterial closed corner. ► A failure envelope based on critical generalized stress intensity factors is obtained.