A micro-mechanics damage approach for fatigue of composite materials

A new model for fatigue damage evolution of polymer matrix composites (PMC) is presented. The model is based on a combination of an orthotropic damage model and an isotropic fatigue evolution model. The orthotropic damage model is used to predict the orthotropic damage evolution within a single cycle. The isotropic fatigue model is used to predict the magnitude of fatigue damage accumulated as a function of the number of cycles. This approach facilitates the determination of model parameters since the orthotropic damage model parameters can be determined from available data from quasi-static-loading tests. Then, limited amount of fatigue data is needed to adjust the fatigue evolution model. The combination of these two models provides a compromise between efficiency and accuracy. Decomposition of the state variables down to the constituent scale is accomplished by micro-mechanics. Phenomenological damage evolution models are then postulated for each constituent and for the micro-structural interaction among them. Model parameters are determined from available experimental data. Comparison between model predictions and additional experimental data is presented.

Dropping the weight stigma: Nostalgia improves attitudes toward persons who are overweight

Weight stigma, a negative attitude toward persons who are overweight, can lead to emotional detriment (increased vulnerability to depression and anxiety, decreased self-esteem) and discriminatory practices (denial of employment, lower wages, refusal of job promotion or college admission, healthcare deprivation), which have increased dramatically in the United States over the past decade. We report two experiments that implicate nostalgia as a resource or strategy for weight stigma reduction. We hypothesized and found that nostalgia about an encounter with a person who is overweight improves attitudes toward the group "overweight." Undergraduates who recalled a nostalgic (vs. ordinary) interaction with an overweight person subsequently showed more positive outgroup attitudes. The effect of nostalgia on outgroup attitudes was mediated by greater inclusion of the outgroup in the self and increased outgroup trust (Experiments 1 and 2), as well as reduced intergroup anxiety and greater perceptions of a common ingroup identity (Experiment 2). The findings have interventional potential. (C) 2011 Elsevier Inc. All rights reserved.

Minding the Gap: Children with Disabilities and the United Nations Convention on the Rights of Persons with Disabilities

This chapter provides a critical assessment of the approach adopted by the United Nations Convention on the Rights of Persons with Disabilities (CRPD) towards children with disabilities and its implications for socializing States Parties to both ‘right’ and ‘rights’ behaviour. It discusses the ways in which ‘rights talk’ for children with disabilities, itself a relatively recent development in this context, has been predominantly needs based in its substantive content, and explores whether the exacerbated disadvantage experienced by children with disabilities as a result of the particular interaction between disability and childhood is effectively addressed and given due weight by the new Convention. The CRPD's provisions are discussed in the context of children with disabilities and their potential to provide effective redress assessed. The chapter concludes with some critical reflections on the extent to which the CRPD can really be understood as minding the gap for children with disabilities.

Fracture mechanics using a 3D composite element

The formulation of a 3D composite element and its use in a mixed-mode fracture mechanics example is presented. This element, like a conventional 3D finite element, has three degrees of freedom per node although, like a plate element, the strains are defined in the local directions of the mid-plane surface. The stress-strain property matrix of this element was modified to decouple the stresses in the local mid-plane and the strains normal to this plane thus preventing the element from being too stiff in bending. A main advantage of this formulation is the ability to model a laminate with a single 3D element. The motivation behind this work was to improve the computational efficiency associated with the calculation of strain energy release rates in laminated structures. A comparison of mixed-mode results using different elements of an in-house finite element package are presented. Good agreement was achieved between the results obtained using the new element and coventional higher-order elements

Progress in Fracture and Damage Mechanics

This special-topic volume reports on new progress made in the analysis and understanding of fracture and damage mechanics. The Finite Element Method is a well-established analytical tool for theoretical fracture analysis. The development of interface elements which combine aspects of both fracture and damage mechanics has permitted the prediction of both crack initiation and propagation. A number of the papers presented here deal with their use and further development.Substantial progress has also been made in the use of the Boundary Element Method for treating crack problems. The inherent mathematical complexity of this method has resulted in somewhat slower progress than that enjoyed by the Finite Element Method and is still the focus of much research. The volume also presents a number of contributions arising from this field. A topic which is closely related to the study of fracture is structural repair. Although repairs are usually effected after fracture occurs, the structural analyst must still ensure that the repair itself is not prone to cracking or other forms of damage. Two approaches to the study of damage in a repaired structure are described in this special volume. These three aspects, taken together, ensure that even the expert will learn something new from this book.