IMECE2002-33575 COHESIVE FINITE ELEMENT BASED MODELING OF DAMAGE IN COMPOSITE MATERIALS

ABSTRACT Damage in composite laminates affects its overall viscoelastic response. Constitutive equations have been developed for composite laminates considering a fixed damage state. A complete description, however, requires suitable damage evolution laws. This paper is focused on studying damage evolution in viscoelastic laminates using a cohesive finite element approach. A two dimensional, four nodded finite element is developed incorporating a rate-independent tractiondisplacement cohesive law. This element is used in conjunction with plane strain bulk elements behaving in a linear viscoelastic manner to simulate crack evolution between two existing transverse cracks in symmetric cross-ply laminates. The effects of loading strain-rate, ply constraint and initial crack density are studied. This study shows expected trends in the behavior and indicates the suitability of cohesive zone modeling to study damage evolution in viscoelastic composite materials

Long term durability of polymer matrix composites for high temperature applications

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Transverse crack formation in unidirectional plies predicted by means of a percolation concept

Transverse crack formation in epoxy based unidirectional composites is treated by means of a percolation concept. A previously proposed criterion for brittle cavitation in epoxies is used as the criterion for fibre/matrix debonding. Then, neglecting the details of debond linkups, a transverse crack is assumed to form when the intensity of the linkup process crosses a threshold analogous to the percolation threshold. The predicted applied strain to transverse crack formation based on this assumption agrees well with experimental data. A parametric study is conducted to reveal the effects of thermal cooldown temperature, fibre volume fraction and fibre elastic properties on the percolation threshold for transverse crack formation

Objedinenie mekhaniki makro- i mikropovrezdenia dlja ocenki funkcionalnykh kharakhteristik kompozitnykh materialov

When subjected to mechanical loads, composite materials can generate complex configurations of multiple cracks that collectively change the average material response and thereby the performance, e.g., the fatigue life. Over many years, various approaches have been developed to predict the properties of composite materials with damage, but none of them is capable of treating other than a few special cases. In this paper, we address the two main approaches, described as macro- and microdamage mechanics, and demonstrate that, by integrating these in a combined approach, an effective methodology for performance evaluation can be achieved to treat a broad range of composite materialsGodkänd; 2012; 20121206 (janis

Continuum damage mechanics : A modeling approach for comprehensive assessment of subcritical damage in composites

The concept of "failure" has served the engineering practice well for designing structures to perform safely in service environments. Historically, this concept has its roots in experience with metals where the onset of undesirable material condition is yielding followed ultimately by unstable behavior characterized by maximum load carrying capacity. This classical concept of material failure was subsequently broadened to include fracture, which deals with onset and instability of growth of a preexisting flaw. In heterogeneous materials, particularly in composites, where multiple materials exist, the failure and fracture concepts are not as straightforward. The concept of damage is instead more useful, with its onset and criticality as two end conditions.Upprättat; 2007; 20130228 (andbra