JEC COMPOSITES MAGAZINE - Issue #42 - July/August 2008 - 59

The approach can be regarded as a further step towards the upstream integration of environmental aspects into the composite product development process. Within this context, we’ll focus specifically on the uniaxial tension test of mechanical characterisation. However, the current approach remains valid and applicable for other types of material characterisation (bending, torsion, shear, etc.). Identifying eco-characterisation coefficients With reference to article [6], the ecodesign model diagram represents the sustainable design function as an intersection between the quality, environment and health functions. The diagram shows that only subset F is fulfilling the ecodesign condition, which may be subjected to an optimisation process. If we assign to each principal function a principal coefficient representing the degree of interaction, it may be considered that: - α is a principal coefficient defining the criterion that assesses technical performance in terms of composite-material quality considerations, - β is a principal coefficient defining the criterion that assesses the material’s performance with regard to the environment, and - γ is a principal coefficient defining the criterion that assesses the material’s performance with regard to health protection. There are several successive sub-stages in the characterisation stage, and we found it convenient to assign a sub-coefficient (i=1, m) to each sub-stage that will provide the probability of approval in terms of quality control. Thus, the assessment of the quality function in relation to the stage of material characterisation will be measured by a principal coefficient α that can be written as: with i<m If we proceed in the same manner for the two other functions, the principal coefficients β and γ for environment and health considerations can be written respectively as: with j<n with k<p Fig. 2: Example of a graph for some eco-coefficient values Integrating qualitative, health and environmental aspects into characterisation tests The risks related to environment and health conditions are taken into account by considering the product of the principal coefficients. For notation simplicity, this product may be reduced and replaced by a coefficient λ, defined as: This coefficient will be inserted into the standard mechanical characterisation formulae of materials. Hence, Young’s modulus of elasticity E, determined by Hooke’s law and derived from experimental results (see figure 1) must be adapted to the actual situation by integrating health and environmental considerations into characterisation tests. With this new E value and from a theoretical point of view, Hooke’s law remains valid. However, this time it may be written as: According to sub-coefficient values ai (i=1,m), bj (j=1,n) and ck (k=1,p), the principal coefficients α, β and γ may approach 0 or be equal to 1. The notion of eco-characterisation is fulfilled when the product of the three principal coefficients is close to 1 ( ). However, it should be noted that the failure of a single coefficient could systematically cause the rejection of the material. For instance, Figure 2 shows some values for these coefficients and their position in comparison with their limiting values. where is the eco-modulus of elasticity. The three dots above the character E are only a brief description of the diagram, illustrated in reference [6], showing interaction between health, quality and environment functions. In other terms, the three dots represent the three “pillars” that characterise the basic elements of the sustainable development concept. In relation to this orientation, the modulus efficiency may be evaluated by measuring the following eco-efficiency ratio of elasticity: No42 July-August 2008 / JEC Composites Magazine
JEC COMPOSITES MAGAZINE - Issue #42 - July/August 2008

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #42 - July/August 2008
