Modeling the Initiation and Growth of Delaminations in Composite Structures

Abstract

A method for modeling the initiation and growth of discrete delaminations in shell-like composite structures is presented. The laminate is divided into two or more sublaminates, with each sublaminate modeled with four-noded quadrilateral shell elements. A special, eight-noded hex constraint element connects opposing sublaminate shell elements, and makes the two opposing shell elements act as a single shell element until a prescribed failure criterion is satisfied. Once the failure criterion is met, the connection is broken, and a discrete delamination initiates or grows. This approach has been implemented in a three-dimensional finite element code. This code uses explicit time integration, and can analyze shell-like structures subjected to large deformations and complex contact conditions. Tensile, compressive, and shear laminate failures are also modeled. This paper describes the eight-noded hex constraint element used to model the initiation and growth of a delamination, and discusses associated implementation issues. In addition, calculated results for double cantilever beam and end notched flexure specimens are presented and compared to measure data to assess the ability of the present approach to model a growing delamination. Results are also presented for a diametrally compressed ring to demonstrate the capability for analyzing progressive failure in a highly deformed composite structure.

Separation force analysis and prediction based on cohesive element model for constrained-surface Stereolithography processes

“…Once traction reaches this critical point, crack starts to grow. Many Computer Aided Design 8 constitutive laws have been proposed in this context to characterize this damage evolution phase (i.e., the crack or delamination growth) including, but not limited to, trapezoidal law [8], perfectly plastic law [9], polynomial law [10], exponential model [33], and bilinear law [7,30,[34][35][36]. In the present work, bilinear cohesive law ( Figure 4) is chosen for further study for illustration purpose.…”

Cohesive zone models and impact damage predictions for composite structures

“…This penalty approach can also be used when layers above and below the interface are modeled as beams, plates or shells. Forces and moments are applied to force the transverse displacements to be the same and to eliminate shear deformations at the interface [200].…”

A mesh-independent interface technology for simulation of mixed-mode delamination growth

“…The damage model implemented in the developed interface element is one that is commonly adopted (Reedy et al, 1997;Davila et al, 2001;Mi et al, 1998;Chen et al, 1999;Alfano and Crisfield, 2001;Lammerant and Verpoest, 1996;Schellekens and de Borst, 1993;Schipperen and Lingen, 1999;Dakshima Moorthy and Reddy, 1999). It mixes features of strength of materials approaches and fracture mechanics.…”

“…At a given point on the interface, the area under the stress-relative displacement curve is equal to G c . This approach to the determination of the delamination growth has been adopted by Reedy et al (1997), Davila et al (2001), Mi et al (1998), Chen et al (1999, Alfano and Crisfield (2001), Lammerant and Verpoest (1996), Schellekens and de Borst (1993), Schipperen and Lingen (1999) and Dakshima Moorthy and Reddy (1999). Interface elements are introduced to connect the individual plies of a composite laminate, but the way this connection is realized can differ.…”