Finite Element Analysis of Instability Related Delamination Growth

Abstract

A parametric study of postbuckled through-width delaminations in laminated coupons was performed. A finite element analysis was developed to analyze the coupons as a combination of linear and geometrically nonlinear components. Because most of the coupon configuration studied behaves linearly, the mixed linear and nonlinear analysis greatly reduced computational costs. The analysis was verified by comparing numerical with exact solutions for simple hypothetical problems. In addition, measured lateral deflections of postbuckled through-width delaminations in laminated coupons were compared with predicted deflections. In the parametric study, stress distributions and strain-energy release rates were calculated for various delamination lengths, delamination depths, applied loads, and lateral deflec tions. Also, a small number of coupons with through-width delaminations were fatigue tested to obtain delamination growth data. Calculated strain- energy release rates were compared with the observed growth rates to deter mine the relative importance of the Mode I and Mode II components of energy release. GI was shown to dominate the growth process.