A study on failure strength evaluation of hybrid composite joint

Abstract

As composites have become popular in recent years, the design of the composite joint has become a very important research area because the structural efficiency of the composite structure is determined by its joints, not by its basic structures. Generally, the joining methods of the composite structures are classified into mechanical and adhesive types. We evaluated the failure strength of the hybrid joints composed of an adhesive bond in conjunction with mechanical fastening. The double lap joint jig was used for the tensile test of the hybrid joint. The 10 hybrid joint specimens which have different width-to-diameter (w/d) ratio, edge-to diameter (e/d) and thickness were manufactured and tested. Carbon-epoxy unidirectional prepreg (USN125) and plain weave prepreg (HPW193) were used for the hybrid composite joint. The stacking sequence of the hybrid composite joint was [±453/90/ ±452/04/90/04/±452/90/ ±453]. To predict the failure Strength of the hybrid joints, finite element analyses were performed using the ANSYS 10.0 commercial soft-ware and 3-D structural solid element. From this study of the failure strength prediction of hybrid joints, the experimental failure loads of the hybrid joints were nearly identical to those of the adhesive joints and were at least twice as large as those of the mechanical joints for all 10 cases investigated. In addition, the adhesive failure in the hybrid joint occurred before the mechanical failure, for all 10 cases investigated. Finally, using the damage zone theory and the failure area index method, the failure load of the hybrid joints could be predicted to within 25.5% for all of the investigated cases. Further study of the dynamic characteristics of hybrid joints, such as fatigue life and crack propagation, is recommended.