an Ashby chart
/ Ashby -> ASH-bee /
An Ashby chart is a map of the whole material world. Each material family is drawn as a bubble, the two axes are two properties (say stiffness versus density), and the result is a scatter plot on which you can see entire kingdoms of material at once.
The axes are logarithmic because properties span many orders of magnitude (density from 0.01 to 20 g/cm^3, modulus from 0.001 to 1000 GPa). Materials fall into natural regions: ceramics top-right (stiff, fairly dense), polymers lower-left, metals in the middle, foams down in the bottom-left. The chart also carries guidelines of slope 1, 2, and 3, matching the indices E/rho, E^(1/2)/rho, and E^(1/3)/rho; you slide such a line across the chart and the last bubbles it touches are your best candidates.
This matters because it turns selection into something you can see: the trade-offs are visible, and so are the empty 'holes' where no material yet exists — which is exactly where a new material would be valuable. Caveat: the bubbles are broad ranges, not exact points, and reading a chart is only step one; real selection still has to layer on cost, process, and shape.
On the classic modulus-density chart (E up the vertical axis, rho along the horizontal, both logarithmic), ceramics sit top-right, metals in the upper middle, polymers lower-left, and foams at the bottom-left. To find the lightest stiff material you lay a line of slope 2 (the E^(1/2)/rho guideline) and slide it up and to the left; the last bubbles it touches — CFRP, engineering ceramics, wood along the grain — are your best candidates.
Reading a material property chart: families cluster, and a sliding guideline of the right slope points to the winners.
The bubbles are broad property ranges, not exact points, and a chart handles only two properties at a time; real selection layers on cost, processability, and shape that no single chart shows.