Wave propagation in fiber composite laminates, part 2

An experimental investigation was conducted to determine the wave propagation characteristics, transient strains and residual properties in unidirectional and angle-ply boron/epoxy and graphite/epoxy laminates impacted with silicone rubber projectiles at velocities up to 250 MS-1. The predominant wave is flexural, propagating at different velocities in different directions. In general, measured wave velocities were higher than theoretically predicted values. The amplitude of the in-plane wave is less than ten percent of that of the flexural wave. Peak strains and strain rates in the transverse to the (outer) fiber direction are much higher than those in the direction of the fibers. The dynamics of impact were also studied with high speed photography

Lamination residual stresses in fiber composites

An experimental investigation was conducted to determine the magnitude of lamination residual stresses in angle-ply composites and to evaluate their effects on composite structural integrity. The materials investigated were boron/epoxy, boron/polyimide, graphite/low modulus epoxy, graphite/high modulus epoxy, graphite/polyimide and s-glass/epoxy. These materials were fully characterized. Static properties of laminates were also determined. Experimental techniques using embedded strain gages were developed and used to measure residual strains during curing. The extent of relaxation of lamination residual stresses was investigated. It was concluded that the degree of such relaxation is low. The behavior of angle-ply laminates subjected to thermal cycling, tensile load cycling, and combined thermal cycling with tensile load was investigated. In most cases these cycling programs did not have any measurable influence on residual strength and stiffness of the laminates. In the tensile load cycling tests, the graphite/polyimide shows the highest endurance with 10 million cycle runouts at loads up to 90 percent of the static strength

Lamination residual stresses in hybrid composites, part 1

An experimental investigation was conducted to study lamination residual stresses for various material and loading parameters. The effects of hybridization on residual stresses and residual properties after thermal cycling under load were determined in angle-ply graphite/Kevlar/epoxy and graphite/S-glass/epoxy laminates. Residual strains in the graphite plies are not appreciably affected by the type and number of hybridizing plies. Computed residual stresses at room temperature in the S-glass plies reach values up to seventy-five percent of the transverse strength of the material. Computed residual stresses in the graphite plies exceed the static strength by approximately ten percent. In the case of Kevlar plies, computed residual stresses far exceed the static strength indicating possible early failure of these plies. Static testing of the hybrids above indicates that failure is governed by the ultimate strain of the graphite plies. In thermally cycled hybrids, in general, residual moduli were somewhat lower and residual strengths were higher than initial values

Strain rate effects on mechanical properties of fiber composites, part 3

An experimental investigation was conducted to determine the strain rate effects in fiber composites. Unidirectional composite specimens of boron/epoxy, graphite/epoxy, S-glass/epoxy and Kevlar/epoxy were tested to determine longitudinal, transverse and intralaminar (in-plane) shear properties. In the Longitudinal direction the Kevlar/epoxy shows a definite increase in both modulus and strength with strain rate. In the transverse direction, a general trend toward higher strength with strain rate is noticed. The intralaminar shear moduli and strengths of boron/epoxy and graphite/epoxy show a definite rise with strain rate

Queue-munity engagement: Collaborative Event Ethnography at the Antiques Roadshow in Kent

Using Collaborative Event Ethnography as a research method, a team of 21 researchers conducted fieldwork at the Antiques Roadshow in Ightham Mote, Kent. This article reflects on the experience of queuing at the event and how it was experienced and discussed by researchers and participants. Drawing upon Mol, the article approaches the practice of queuing as involving an inherent multiplicity of often contradictory experiences through which idealised, Second World War-related understandings of British queuing practice are simultaneously confirmed and challenged. Through multiple participants viewing the queue from within and outside we were able to capture the processes of community-building, curation, management, rule-maintenance and rule-bending within the social life of the queue. In demonstrating this multiplicity Collaborative Event Ethnography is shown to be an excellent research tool for capturing short-term, large-scale events while also highlighting the simultaneous simplicity and complexity of social interactions and social norms within queues

Examination of risk exposure models during COVID-19 in relation to youth life satisfaction and internalizing symptoms

This study examined mediation of a negative COVID-impact on the relationship between risk exposure, and life satisfaction and internalizing symptoms in youth (aged 9-18). Four operationalizations of risk exposure were applied; an Additive versus a Cumulative Risk Model (ARM and CRM), risk clusters and the most salient risk factors. Results showed that a stronger negative COVID-impact is related to lower life satisfaction, more internalizing symptoms and higher additive and cumulative risk. ARM and CRM's effect on lower life satisfaction is mediated through negative COVID-impact, though not for internalizing symptoms. Clusters of risk factors and risk factors within clusters significantly related to a stronger negative COVID-impact are the clusters 'Individual factors' (low self-control), 'Parenting' (negative mother-child interaction and low parental responsiveness), 'Maternal mental health' and 'Demographic factors' (low SES and high paternal education). From all significant risk factors, low self-control, low parental responsiveness, negative mother-child interaction and low SES were most salient

The Relation of Severity and Comorbidity to Treatment Outcome with Cognitive Behavioral Therapy for Childhood Anxiety Disorders

The present study investigated the impact of comorbidity over and above the impact of symptom severity on treatment outcome of Cognitive Behavioral Therapy for children with anxiety disorders. Children (aged 8–12, n = 124) diagnosed with an anxiety disorder were treated with a short-term CBT protocol. Severity was assessed with a composite measure of parent-reported behavior problems. Two approaches to comorbidity were examined; “total comorbidity” which differentiated anxiety disordered children with (n = 69) or without (n = 55) a co-occurring disorder and “non-anxiety comorbidity’ which differentiated anxious children with (n = 22) or without a non-anxiety comorbid disorder (n = 102). Treatment outcome was assessed in terms of Recovery, represented by post-treatment diagnostic status, and Reliable Change, a score reflecting changes in pre- to post-treatment symptom levels. Severity contributed to the prediction of (no) Recovery and (more) Reliable Change in parent-reported internalizing and externalizing symptoms and self-reported depressive symptoms. Total and non-anxiety comorbidity added to the prediction of diagnostic recovery. Non-anxiety comorbidity added to the prediction of Reliable Change in parent reported measures by acting as a suppressor variable. Non-anxiety comorbidity operated as a strong predictor that explained all of the variance associated with severity for self-reported depressive symptoms. The results support the need for further research on mechanisms by which treatment gains in children with higher symptom severity and non-anxiety comorbidity can be achieved

Principios jurídicos que regulan la gestión de cuencas en Argentina

Este proyecto de investigación aborda desde la ciencia jurídica los instrumentos de ordenamientoambiental del territorio. Su objetivo general es analizar los mecanismos de ordenamiento territorialvigentes en la Provincia de Mendoza y su conexidad con los restantes institutos de gestiónambiental, y para ello se procura indagar las instituciones y procedimientos introducidos a partir dela Ley 8051, constatar su compatibilidad con las instituciones de tutela ambiental previstas en la ley5961, y analizar las adecuaciones normativas que exige la integración entre ambas normas.Metodológicamente, presenta un diseño observacional no experimental basado en estrategiascualitativas. A partir de la recopilación de instrumentos jurídicos, se procura la determinación de losmecanismos de resolución de conflictos disponibles en la materia y la consideración de lasventajas comparativas entre los mismos. Los beneficiarios de este trabajo resultan los intérpretesdel orden normativo, tanto los operadores jurídicos (abogados, jueces, funcionarios) como losdestinatarios de las normas (ciudadanos, organismos, ONGs)