Statistical Investigation of Parameters Influence on Fracture Toughness of the Glass Fiber Reinforced Composites
The objective of the work was to investigate statistical analysis of fracture toughness of the glass fiber reinforced composites at different stacking sequences, strain rate and crack length. The glass reinforced vinylester composites prepared by hand layup technique with stacking sequences of 0/90, 45/-45 and chopped strand orientations. 3- point bending for fracture toughness test for various notch depth ratio's as per linear elastic fracture mechanics concept was conducted. Further the initial notch depth method was adopted to find the critical stress intensity factor KIC for the given notch depth ratio. Design of experiment using Taguchi L9 array was formulated to understand the influence of parameters on fracture toughness. The result of surface methodology showed the stacking sequence of (45/- 45/0/90/Chopped)3s, with strain rate of 0.5 mm/min and without notch having the highest fracture toughness of 81.36 Mpa
Residual strength after fatigue in composites: Theory vs. experiment
State-of-the-art phenomenological residual strength models are discussed in this paper. The presentation focus is on probabilistic and deterministic theories that predict strength degradation under various loading conditions. In an effort to improve the predictions, simple modifications on existing models as well as a new one are implemented in computational schemes and predictions are compared to experimental data from C/Ep and Gl/Ep laminates. Theoretical aspects either as deterministic degradation curves or probability distributions are evaluated. The results show that no model is consistent in accurately predicting residual strength degradation behaviour of the different composite laminates, even though some models appear to be more fit to purpose. Statistical predictions at various stress levels and life fractions are also poor. The main conclusion is that the use of complicated phenomenological models requiring large experimental data sets for implementation does not necessarily pay back in terms of accurate predictions and consequently simple models requiring limited experimental effort should be preferred.
Warm Hands in Cold Age – On the Need of a New World Order of Care
The world is aging as fertility and mortality are both decreasing. This article focuses on practical care work for the elderly. Such work is done primarily by women even though a larger portion than previously is paid rather than unpaid. All over the world, most elderly care work is organized within the family, most often unpaid. Men receive more care from partners than women, while women receive more care from female relatives. When care work is paid, the payment is generally low. A comparison between Germany, Spain, and Sweden demonstrates similar gender patterns, even though the role of the state in supporting care differs considerably as do care workers' conditions. The sustainability of today's distribution and organization of care work is questioned as the need for care increases, and the possibility of more equal sharing of care work between women and men is explored.