High-performance composite from epoxy and glass fibers : morphology, mechanical, dynamic mechanical, and thermal analysis

Diglycidyl ether of bisphenol-A type epoxy resin cured with diamino diphenyl sulfone was used as the matrix for fiber-reinforced composites to get improved mechanical and thermal properties for the resulting composites. E-glass fiber was used for fiber reinforcement. The morphology, tensile, flexural, impact, dynamic mechanical, and thermal properties of the composites were analyzed. The tensile, flexural, and impact properties showed dramatic improvement with the addition of glass fibers. Dynamic mechanical analysis was performed to obtain the Tg of the cured matrix as well as the composites. The improved thermal stability of the composites was clear from the thermogravimetric analysis. Scanning electron micrographs were taken to understand the interfacial adhesion between the fiber and the matrix. The values of mechanical properties were compared with modified epoxy resin composite system. Predictive models were applied using various equations to compare the mechanical data obtained theoretically and experimentally.

The effect of simulated thermomechanical processing on the transformation behavior and microstructure of a low-carbon Mo-Nb linepipe steel

The present work investigates the transformation behavior of a low-carbon Mo-Nb linepipe steel and the corresponding transformation product microstructures using deformation dilatometry. The continuous cooling transformation (CCT) diagrams have been constructed for both the fully recrystallized austenite and that deformed in uniaxial compression at 1148 K (875 °C) to a strain of 0.5 for cooling rates ranging from 0.1 to about 100 K/s. The obtained microstructures have been studied in detail using electron backscattered diffraction complemented by transmission electron microscopy. Heavy deformation of the parent austenite has caused a significant expansion of the polygonal ferrite transformation field in the CCT diagram, as well as a shift in the non-equilibrium ferrite transformation fields toward higher cooling rates. Furthermore, the austenite deformation has resulted in a pronounced refinement in both the effective grain (sheaf/packet) size and substructure unit size of the non-equilibrium ferrite microstructures. The optimum microstructure expected to display an excellent balance between strength and toughness is a mix of quasi-polygonal ferrite and granular bainite (often termed “acicular ferrite”) produced from the heavily deformed austenite within a processing window covering the cooling rates from about 10 to about 100 K/s.

Heat affected zone microstructures and their influence on toughness in two microalloyed HSLA steels

Microstructures and Charpy impact properties have been examined in two microalloyed steels following heat treatments to simulate weld heat affected zone (HAZ) structures over a range of heat input conditions, characterised by the cooling time from 800 to 500°C (Δt8/5). The base materials were low carbon structural steel plates microalloyed with vanadium and nitrogen (V-N) and niobium (Nb), respectively. The toughnesses of the HAZs displayed remarkably different behaviours as shown by their impact transition temperatures. For the V-N steel, the toughness improved with increasingly rapid cooling (low heat input conditions) whereas the Nb steel showed an opposite trend. Some of this behaviour could be explained by the presence of coarse ferrite grains in the slowly cooled V-N steel. However, other conditions where all the structures were bainitic and rather similar in optical micrographs gave widely different toughness values. The recently developed method of five dimensional boundary analysis based on electron backscattering diffraction has been applied to these cases for the first time. This showed that the lath boundaries in the bainite were predominantly on {1 1 0} planes of the ferrite and that the average spacing of these boundaries varied depending on steel composition and cooling rate. Since {1 1 0} is also the slip plane in ferrite, it is considered that close spacing between the lath boundaries inhibits general plasticity at stress concentrations and favours initiation of fracture. The differences between the two steels are believed to be due to their transformation behaviours on cooling where precipitation of vanadium nitride in austenite accelerates ferrite formation and raises the temperature of the phase transformation in V-N steels.

A case for cross layer design: the impact of physical layer properties on routing protocol performance in MANETs

In this work we evaluate the performance of routing protocols for mobile ad hoc networks using different physical layer models. The results obtained show that the performance results obtained using idealized models such as the free space propagation model vary significantly when propagation effects such as path loss and shadowing are considered. This difference in performance indicates that optimization is required in the protocol development space that takes into account channel state information (CSI). Such an optimization requires a cross layer approach to be adopted and a framework for protocol performance evaluation to be established. We believe that this work would serve as a first step in this direction. We provide comparative performance results through network simulations.

An investigation of the psychometric properties of the Eating Disorder Symptom Impact Scale within an Australian sample

Caring for patients with an eating disorder (ED) is associated with a high level of burden and psychological distress. Currently, the Eating Disorder Symptom Impact Scale (EDSIS) is the only scale that measures the specific impact of caring for a patient with an ED. The initial development study within a British sample of carers indicated that the EDSIS has a four-factor structure. The aim of the current study was to confirm the factor structure of the EDSIS within an Australian sample of carers. One hundred and fifty-four carers completed the EDSIS. In contrast to the initial study, a six-factor structure was derived explaining 69.66% of the variance: guilt, social isolation, confrontational behaviours, binge–purge difficulties, mealtime difficulties, and illness awareness. Reliability was acceptable (Cronbach's alpha range 0.69–0.88). Five of the six factors were moderately correlated with the General Health Questionnaire-12 (r range = 0.24–0.51). A six-factor solution may be a valid alternative for the EDSIS.

The impact of degumming conditions on the properties of silk films for biomedical applications

The degumming process to remove sericin decreases silk fiber strength; however, the impact of degumming on the mechanical properties of regenerated silk biomaterials has not been established. This study investigated the effect of degumming temperature, time, alkaline component and alkaline concentration on the mechanical properties of silk fibroin films. Sericin removal was estimated using weight loss; 10 samples with 12.2–29.4% weight loss were then further characterized in terms of fiber mechanical properties, fiber surface morphology, molecular weight distribution and film tensile strength. A negative correlation was found between weight loss and fiber tensile strength. This loss of fiber strength under harsher degumming conditions had a direct impact on the tensile strength of regenerated films. Mild degumming conditions (weight loss of 12.2%) led to higher film strength (8.9 MPa), whereas aggressive degumming conditions (with 29.4% weight loss) resulted in significantly weaker films (4.3 MPa). The presence of some residual sericin, after mild degumming, is likely to affect the mechanical properties of the regenerated silk films. These results will assist in the development of materials with mechanical and biocompatibility properties tuned to specific biomedical applications.

The impact of work settings on organisational performance measures in built facilities

A current facilities management discourse seeks to discover how the built environment promotes or retards organisational change. However, whether or not significant change arises at all is yet to be definitively established. Hence, a contribution to the school of thought in this direction is considered important. This research investigated organisational performance relative to innovative work settings. The aim of the study was to determine whether organisational performance and, hence, change are indeed brought about by innovative work settings. A sample of 102 work settings was studied, and several null hypotheses on innovative work settings and organisational performance were tested using the Kruskal-Wallis H test. Although subtle shifts were observed in the aspects of organisational performance that seem predicated on innovative work settings, to some extent the proposition that the physical properties and design of the workplace can influence organisational performance was validated.

Quality of life instruments for caregivers of patients with cancer : A review of their psychometric properties

The quality of life of caregivers of patients with cancer is an important construct given the substantial impact of caring on the physical, psychological, social, and financial well-being of caregivers. Moreover, caring for patients with cancer also affects family functioning and places burdens on caregivers. The reliability and validity of instruments used to assess the quality of life of caregivers of patients with cancer were reviewed to aid in the selection of the most appropriate measures For research and practice. MEDLINE (1980-2000) and c/NAHL (1982-2000) searches located relevant quality of life instruments using the keywords "cancer and quality of Iife" and "caregiver or spouse or partner." The search identified the following instruments: the Caregiver Quality of life Index-Cancer Scale, the 'Caregiver Quality of Life Index, the Quality of Life Tool, and the Quality of life Index-Cancer Version. Quality of life instruments developed specifically to measure the quality of life of caregivers of patients with cancer had the best psychometric properties. The Caregiver Quality of Life Index-Cancer Scale, in particular, met or exceeded minimum psychometric criteria for reliability and validity. The development of reliable and valid caregiver quality of life measures is an important factor in developing interventions to enhance quality of life of caregivers of patients with cancer.

Internal consistency and validity of the Stroke Impact Scale 2.0 (SIS 2.0) and SIS - 16 in an Australian sample

Background and Purpose: The impact of stroke is multidimensional however standard stroke measures do not discriminate well when stroke patients are less physically impaired. The Stroke Impact Scale 2.0 (SIS 2.0) is a multidimensional measure of the impact of stroke but its'' psychometric properties require further testing. The SIS-16 is a measure of physical functioning designed to be more sensitive to differences in physical functioning than current stroke outcome measures but there is only preliminary information detailing its'' reliability and validity. The current study examined the internal consistency and validity of the SIS 2.0 and SIS-16 in an Australian sample of stroke patients. Methods: The SIS 2.0, SIS-16, World Health Organization Bref-Scale (WHOQOL-BREF) and Zung''s Self-Rating Depression Scale (SDS) were completed by 74 stroke patients in rural Victoria, Australia.
Results: The item convergent validity index indicated good item convergence of the SIS-16 and SIS 2.0 domains. The item discriminant validity index had only adequate divergence for most SIS 2.0 domains. Internal consistencies of the SIS-16 and SIS 2.0 domains were acceptable (agr = 0.87–0.95). Correlations between the SIS-16 and SIS 2.0 and the WHOQOL-BREF and SDS supported the convergent and discriminant validity of the SIS-16 and all the dimensions of the SIS 2.0 except lsquoParticipationrsquo which lacked discriminant validity. Conclusions: The SIS 2.0 and SIS-16 had good psychometric properties with support for the internal consistency and validity of both measures.

Paediatric quality of life instruments: a review of the impact of the conceptual framework on outcomes

With an increasing number of paediatric quality of life (QOL) instruments being developed, it is becoming difficult for researchers and clinicians to select the most appropriate instrument. Reviews of QOL instruments tend to report only basic properties of the instruments such as domains and psychometric properties. This paper seeks to appraise critically the conceptual underpinnings of paediatric QOL instruments. A systematic review was conducted to identify QOL instruments for children aged 0 to 12 years, and to examine and compare their conceptual frameworks, definitions employed, and structure. Both generic and condition-specific measures were reviewed. Fourteen generic and 25 condition-specific QOL instruments were identified. Eleven types of definition of QOL and health-related QOL and three theories of QOL were identified. QOL was measured by a variety of domains including emotional, social and physical health, and well-being. Items commonly assessed difficulties, or intensity/frequency of feelings/symptoms, in contrast to positive aspects of life and happiness. The findings highlight the diversity that is apparent in the conceptualization of paediatric QOL and draw attention to the lack of empirical evidence for many of the fundamental assumptions. The impact of the conceptual underpinnings of the instruments on the resulting QOL scores is discussed.

An experimental study of low velocity impact response in 2/2 twill weave composite laminates manufactured by a novel fabrication process

A novel fabrication process for advanced composite components—the QuicktepTM process was described. 2/2 twill weave MTM56/CF0300 carbon epoxy composite laminates were manufactured by the Quickstep and the autoclave processes. The response of these laminates to drop-weight low velocity impact at energy levels ranging from 5 to 30 J was investigated. It was found that the laminates fabricated by the Quickstep had better impact damage tolerance than those fabricated by the autoclave. Optical microscopy revealed extensive matrix fracture in the center of the backside of the autoclave laminates indicating the more brittle property of the epoxy matrix cured by the autoclave process. Interfacial shear strength (IFSS) for two composite systems were measured by micro–debond experiments. The MTM56/CF0300 material cured by the Quickstep showed stronger fibre matrix adhesion. Since the thickness and density of the impact targets produced by two processes were different, finite element analysis (FEA) was performed to study the effect of these factors on the impact response. The simulation results showed that the difference in thickness and density affects the stress distribution under impact loading. Higher thickness and lower density caused by processing lead to less endurance to drop weight impact loading. Therefore the better performance of Quickstep laminates under impact loading was not due to the thickness and density change, but resulted from stronger mechanical properties.

Impact of ripening stages of banana flour on the quality of extruded products

The study investigated the physical, nutritional and sensory properties of different ripening stages of banana during extrusion processing in combination with rice flour to develop quality snack products. Dehydrated banana flours at ripening stages 4, 5 and 6 (peel colour) were mixed separately at 40% banana to 60% rice flour levels. The mixtures were extruded through a twin-screw extruder at 120 °C barrel temperature, 220 and 260 r.p.m, screw speed and 12% feed moisture. Increase in ripeness indicated negative effect on expansion and water absorption capacity while increasing the water solubility index and moisture retention (wet basis) of the products. Protein and mineral (except for zinc and copper) content of the products were significantly different (P < 0.05) from 4 to 6 of the ripening stages. Most of the essential amino acids in the extruded products increased significantly (P < 0.05) at the ripening stage of 6. All the products were within the acceptable range in the 9-point Hedonic scale showing the best texture and flavour scores for stage 4 and 6, respectively. The extruded products show potential as snack products because of their nutritional quality and sensory acceptability.

Compressive properties and energy absorption of hollow sphere aluminium

Manufactured cellular aluminums have been developed for a wide range of automotive applications where weight savings, improved safety, crashworthiness and comfort are required. The plateau deformation behavior of cellular aluminums under compressive loading makes this new class of lightweight materials suitable for energy absorption and comes close to ideal impact absorbers. In the present study, aluminum hollow hemispheres were firstly processed by pressing. Hollow sphere aluminum samples with a body-centered cubic (BCC) packing were then fabricated by bonding together single hollow spheres, which were prepared by adhering together hollow hemispheres. Hollow sphere aluminum samples with various kinds of sphere wall thicknesses of 0.1 mm, 0.3 mm and 0.5 mm but the same outside diameter of 4 mm were investigated by compressive tests. The effects of the sphere wall thickness on the mechanical properties and energy absorption characteristics were investigated.