A Framework for the Meeting & Workshops
The framework upon which the major themes of the Meeting and Workshops are placed and the connections and continuity between them is illustrated in the Figure. We observe the hierarchy of structural scales from the micron to the metre (and greater) level of size. Also indicated are the discrete methods of analysis ranging from micro-mechanical (mechanism) modelling to the continuum levels of mathematical prediction of the complete design process.
Hierarchy of structural scales ranging from the micron to the metre level of size;
from the single fibre to the single ply, and from the laminate coupon to the final structure.
The concept of multi-scaling emerges where multi-function materials can be designed to satisfy several criteria simultaneously. Designers and engineers are freed from the bondage of having to apply technologies that are tied to material homogeneity. Advanced interpretation of reliability and durability for sub-micron size devices is being sought that no doubt will be the challenge of the 21st century. Multi-scale problems have to be addressed by appropriate inter-disciplinary multi-scale modelling methods. The entire range of length scale has to be probed if we are to understand issues that limit the performance of the material on the one hand and engineering structure on the other. Understanding processes or mechanisms that operate in the material at all length scales and reconciling them with component durability and reliability is one of the ultimate challenges.We identify permissible limits on safe performance of the material on the one hand and the enduring component on the other. This will provide us with scope for optimisation, where composite material properties vary continuously with some internal parameter that relates to composite architecture in some way. Then, when a set of properties is specified, it should be possible to select a particular lay-up or weave of an appropriate composite material system, and processing conditions, to meet that specification.
Complementary to the unification of the multi-scale modelling methods, of the continuum and micro-mechanics approaches, more work is required into the development of the probabilistic approach. Not much has been done in this direction since Waloddi Weibull presented his work 50 years ago. As composite materials are stretched towards their limit, the statistical variation in their properties becomes more apparent. Always, one is working on the tail of the distribution, where the probability of failure is great. Predicting failure probabilities under extreme conditions is highly desirable.