Generation of a short fibre biocomposite representative volume element

One of the greatest challenge in working with natural fibre composites is the large variation in mechanical properties that result from the geometric inconsistency amongst fibres. Traditional design tools and models are unable to accurately incorporate this non-homogeneity to predict the resulting local behaviour of biocomposite materials. The following paper presents a methodology to generate a representative volume element (RVE) to simulate the material microstructure of short fibre composites, with the intent of modelling the popular class of short fibre biocomposites materials. The capabilities of a range of particle packing algorithms used in literature are compared in terms of the maximum volume fraction they have been able to achieve and for what fibre length to diameter aspect ratio. The methodology is able to account for the characteristics of fibre geometry samples, according to their probability density functions (PDFs). The RVE generation strategy imposes periodic boundary conditions and fibres are declared invalid if an intersection between fibres is detected. The effect of different PDFs on the resulting RVE are discussed. An RVE populated with data following a Weibull distribution is compared to that from normally distributed data with an equal mean but varied standard deviations. Using a Weibull distribution to simulate the characteristics of an RVE requires a significantly higher number of fibres than any comparable normal distribution, due to the skewness of the data towards large values at low probabilities. The highest volume fraction achieved was 40% for an RVE containing fibres with lengths distributed according to a Weibull distribution and aspect ratios of 15. The future intent of this work is to perform finite element analysis on RVE samples with a range of varied microstructure characteristics to determine the effect on overall composite properties, which will provide new insights on how best to formulate short fibre compounds

СОСТОЯНИЕ И ПЕРСПЕКТИВЫ ПРОМЫШЛЕННОГО ПТИЦЕВОДСТВА РЕСПУБЛИКИ БЕЛАРУСЬ

Glue laminated timber is currently manufactured using classical adhesives such as resorcinol formaldehyde and phenol resorcinol formaldehyde. These are proven structural adhesives; however their long cure times and rising costs are creating opportunities for newer technology adhesives. One such class are the structural polyurethanes with decreased spread rates and faster curing times. Their limitation lies in their inability to adhere timbers of densities exceeding 800 kg/m(3). When used on species including the southern pines (Pinus spp.) with a high frequency of latewood, they delaminate after accelerated weathering tests due to stresses imposed on the glue line during the drying process. Surface incision has been trialed in this study to increase the penetration of polyurethane adhesives and reduce glue line stresses. The study shows that incisions to a depth of 2 mm decreases delamination when compared to matched samples with no incisions. The significant increase in glue line surface area may result in stress reduction as the more compliant adhesive may distribute the stresses better across the glue line. Furthermore, microscopic analysis suggests that the incisions are reducing glue line stress through crack propagation into the timber pointing to the possibility of increased timber compliance at the glue line

Literature review of natural fibre composite fire properties

The past decade has seen an increase in natural fibre composite research, with a focus towards improving mechanical properties to compete with traditional composites. Despite this academic interest, the commercial interest and uptake is comparatively small. Furthermore, the commercial applications are also not driven by mechanical properties, but other features. One is the fire performance of natural fibre composite, and integrating with a commercial light resin transfer moulding (RTM) process. In flammability research of natural fibre composites, there is a general formula that researchers follow: select fibre/matrix combination(s), select retardant additives or processes, manufacture sample, test samples, and discuss findings. This formula has been pivotal in establishing the type of retardants and processes that are capable of reducing the flammability of bio-composites. The following report provides a review of current literature on fire properties. It reviews the behaviour of natural fibre composites during a fire, including a common testing method, and the results obtained from this process. The report also reviews common fire retardant additives which can be used with natural fibre composites. Finally, it identifies areas of future research that will contribute to the fire properties body of knowledge

Representations and concepts of professional ethos among Swiss religious education teacher trainers

Over the past two decades, the organisation of religious education classes in Switzerland has undergone profound reforms. Amid the increasing secularisation and pluralisation of the religious landscape, many cantons have introduced a compulsory course that falls under the responsibility of the state and is aimed at teaching basic knowledge about a variety of religions. These reforms have enabled a harmonisation of the syllabi for religious education across the country and have prompted the adaptation of teacher training programmes. Because of the many diverse social expectations surrounding these new courses and the diverse academic tra- ditions in the field of religious education, however, a unified conception of these courses is still absent. In this article, we discuss the ongoing construction of religious education teachers’ professional ethos within this fluid context. In particular, we discuss the perspective of teacher trainers on pragmatic questions concerning religious plurality and the place of teachers’ and pupils’ personal (religious) experiences in the classroom, and pay attention to different representations of ‘religion’ and distinct ideas regarding the purpose of these courses as they have a major impact on the professional attitudes expected from teachers. Keywords: professional ethos; teacher trainers; Switzerland; concepts of religion; impartialit