Progressive Failure Analysis of Composite Honeycomb Sandwich Panels

Abstract

Composite honeycomb sandwich structures are being widely used in the aerospace industry as a light weight structural design. However, the residual strength (damage tolerance) analysis required to address the vulnerability of such structures after the impact damage has proven difficult to perform with confidence. An integrated progressive failure analysis method is developed herein that simulates the progressive intra/inter laminar failure mechanisms observed in composite honeycomb sandwich structures. This method adopts a continuum damage mechanics approach and modifies the stiffness degradation scheme to enable prediction of the intralaminar matrix cracking and fiber fracturing. It also applies integrated VCCT/Cohesive method to allow the explicit modeling of interlaminar failure – the debond/delamination growth from the structural flaw, as well as the formation of the secondary debond/delamination that eventually merges with the primary damage to precipitate the ultimate failure of certain composite honeycomb sandwich structures. The formulation of the method are derived rigorously and summarized in this paper. The analysis predictions are correlated against existing test data for various honeycomb sandwich structures with an embedded flaw that fails in different failure modes.