Learning to co-operate: youth engagement with the co-operative revival in Africa

Co-operatives are seen to offer alternatives for individuals to improve livelihoods. However they have a mixed record, especially in Africa. Initially controlled by the state, many co-operatives did not survive with the advent of structural adjustment policies. However there is now a revival. In parallel, some countries have policies to engage youth in co-operatives. Can co-operatives, as socially-oriented businesses, throw off their history and provide an opportunity for youth? This article examines this question by combining extensive field data from youth co-operatives in Uganda and Lesotho with situated learning and human development theories. It finds that contemporary co-operatives and their networks provide an ‘expanded learning space’ for youth, although there is differentiation by education and gender and type of co-operative. The article makes a novel contribution to debates about co-operatives in development and their potential to provide an alternative route for youth futures

An investigation of stress concentration, crack nucleation, and fatigue life of thin low porosity metallic auxetic structures

This paper investigates, both experimentally and numerically, the mechanical response of low porosity thin metal samples under fatigue loads. The specimens, characterized by an overall porosity of 10%, were designed using selected patterns of voids and then fatigue tested to estimate the influence of both auxetic and non-auxetic tessellations on the mechanical performance. During the loading, detailed deformation maps were recorded by means of bi-dimensional Digital Image Correlation (DIC). The experimental data collected during this study indicate that the use of auxetic patterns could be a strategy to enhance the fatigue life of porous structures. In addition, DIC analysis is shown to be an excellent non-contact experimental method to assess the cumulative damage of the samples and to predict the crack starting points well before they are detectable by the unaided eye

A novel auxetic structure with enhanced impact performance by means of periodic tessellation with variable poisson’s ratio

This study proposes a new approach to designing impact resistant elastomeric structures using innovative bi-dimensional patterns composed of a combination of circular and elliptical voids with variable aspect ratios. Key to the design are discrete sections each with different effective Poisson’s ratios ranging from negative to positive. Cubic samples 80 × 80 × 80 cm in size with different void geometry and effective Poisson’s ratios were fabricated and successively tested under compressive and low-velocity impact loads as a proof-of-concept, showing good agreement with finite element simulations. The numerical comparisons for different porosity levels demonstrated that the variable Poisson’s ratio materials resulted in better impact responses compared to those characterized by a positive (constant) value of the effective Poisson’s ratio. The promising results also show that the variable shape of the voids can lead to a modular trigger of overall effective auxetic behavior, opening up new ways design and use auxetic macro-structures with variable porosity and variable Poisson’s ratio for a wide range of applications and, in particular, for impact and protecting devices