161 Introduction viability

The viability of a foam in a given application depends on the balance between its performance and its cost. There are three steps in evaluating it (Figure 16.1).

The first is the technical assessment (Figure 16.1, upper circle). Performance metrics are identified and evaluated for competing solutions for the design. Examples of technical models can be found in Chapter 5.

The second step is the analysis of cost (Figure 16.1, lower-left circle): how much does it cost to achieve a given performance metric? The quantity of foam required to meet constraints on stiffness, on strength, on energy absorption, etc. is calculated from straightforward technical models. The cost, C, of producing this quantity of material in the desired shape is the output of the cost model, as described in Section 16.3.

Figure 16.1 The three parts of a viability assessment

The final step is that of assessing value (Figure 16.1, lower-right circle): is the change in performance worth the change in cost? Balancing performance against cost is an example of multi-objective optimization. This is discussed in Section 16.4

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