Application of Analytic Models for Thin Embedded Delamination Buckling in Composite Material Panels

Abstract

The presence of delaminations significantly reduces the resistance of structural composite components under compressive loads; indeed, the delamination growth may lead to premature failure of the entire structure. Using non-linear FEM analyses for delamination buckling and growth simulation with the VCCT techniques, even if accompanied by global/local coupling, is still unsuitable for preliminary design and optimization of composite structures. For this reason, in the design of aerospace composite structures, a strength reduction factor to the materials allowables is introduced to take into account the strength reduction induced by these defects. Faster methodologies (analytic and/or empirical) for the evaluation of delamination buckling and growth initiation critical loads are desirable in order to support the effective “damage-tolerant” design of composite structures. The most adopted method for the delaminations analyses is the Raleigh-Ritz energetic method, used with a guessed buckled shape of the delamination. This paper presents a new analytic model for the calculation of both the global buckling load of a delaminated plate and the local buckling load of delaminations with different shapes; the method is then applied to several test cases for validation purpose.