Use the modulus-relative cost chart of Figure 4.7 to find,...

Use the modulus-relative cost chart of Figure $4.7$ to find, from among the materials that appear on it: (a) The cheapest material with a modulus greater than $1 \mathrm{GPa}$. (b) The cheapest metal. (c) The cheapest polymer. (d) Whether magnesium alloys are more or less expensive than aluminum alloys. (e) Whether PEEK (a high-performance engineering polymer) is more or less expensive than PTFE.

Use the modulus-relative cost chart of Figure $4.7$ to find, from among the materials that appear on it:
(a) The cheapest material with a modulus greater than $1 \mathrm{GPa}$.
(b) The cheapest metal.
(c) The cheapest polymer.
(d) Whether magnesium alloys are more or less expensive than aluminum alloys.
(e) Whether PEEK (a high-performance engineering polymer) is more or less expensive than PTFE.

Key Concepts

Material Selection Process

The material selection process involves evaluating different materials based on a variety of criteria, including mechanical properties like modulus, relative cost, and other factors like environmental impact and manufacturability. This systematic approach helps engineers choose the best material for a given application while meeting performance and budgetary requirements.

Material Classification

Materials are typically categorized into classes such as metals, polymers, ceramics, and composites. Each class exhibits distinct performance characteristics and cost ranges. Recognizing these classifications is crucial when comparing materials, as it helps in identifying the most appropriate class based on both mechanical performance and economic factors.

Relative Cost Analysis

Relative cost analysis is the practice of comparing the expense of materials on a normalized scale, often in relation to a specific property like elastic modulus. This approach allows engineers to identify cost-effective options by balancing performance parameters with economic considerations, rather than just comparing absolute prices.

Modulus-Relative Cost Chart

This chart is a tool used to compare materials by plotting their elastic modulus against their relative cost. It enables designers to quickly assess which materials offer the best balance between stiffness and cost, helping in preliminary material selection decisions in engineering design.

Elastic Modulus

Elastic modulus is a fundamental material property that measures a material's stiffness, or its resistance to elastic deformation when a load is applied. It serves as a key indicator of how much a material will flex under stress, and is critical in selecting materials for applications where rigidity is required.

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