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# General material properties - A211

General material properties
Foundational knowledge article
Document Type Article
Document Identifier 211
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## Overview

This page provides links to general material properties. In the Knowledge in Practice Centre (KPC), general material properties are defined as properties that apply to all material classes – properties applying to all materials, and not necessarily specific to only polymer matrix composites or their individual constituent material components.

Below are general material property pages found in the KPC:

## Thermal Properties

### Specific heat capacity

Heat capacity $$C$$ is the material property representing a material’s ability to absorb heat from its external surroundings [1]. It is the ratio of the heat that must be added to or withdrawn from a system for a resulting change in the system’s temperature [2]. Specific heat capacity $$c_p$$ is defined as the quantity of energy required to raise the internal heat of a material one degree, under specified conditions, per unit mass of material, without causing a phase change [3]. $$c_p$$ is defined under constant pressure conditions, while $$c_v$$ is specific heat under constant volume conditions. For solids, $$c_p$$ and $$c_v$$ are nearly identical in value [4].

Specific heat capacity $$c_p$$ is expressed as:

$$c_p=\frac{1}{m}\cdot\frac{dQ}{dT}$$

With,

$$dQ=$$ Energy required to produce the temperature change [J]

$$dT=$$ Temperature change [K]

$$m=$$ Mass of material heated [kg]

### Thermal conductivity

Thermal conductivity, $$k$$, is defined as the material property measuring a material or medium’s ability to transport heat energy. Materials with a high thermal conductivity are highly conductive materials, and are considered to transport heat internally at a high rate. While insulators are defined as materials with a low thermal conductivity value, and transport heat slowly.

It is defined as a physical constant $$k$$ from Fourier's Law. In the 1-D heat flow scenario, Fourier's Law can be defined as:

$$q=-k\frac{dT}{dx}$$

Where,

$$q$$ = heat flux [J/m2·s]

$$k$$ = thermal conductivity [W/m·K]

$$\frac{dT}{dx}$$ = temperature gradient [K/m]

### Thermal diffusivity

Thermal diffusivity, $$\alpha$$, is a quantitative measure of how a material will respond to transient thermal conditions. It is defined as the ratio of thermal conductivity to the volumetric heat capacity of the material (density times the specific heat capacity).

Thermal diffusivity $$\alpha$$ is calculated as:

$$\alpha=\frac{k}{\rho c_p}$$

Where,

$$k=$$ Thermal conductivity [W/m·K]

$$\rho=$$ Material density [kg/m3]

$$c_p=$$ Specific heat capacity [J/kg·K]

Together, the bottom terms ($$\rho c_p$$) represent the volumetric heat capacity [J/m3·K].

## Chemical Properties

Coming soon.

• Corrosion resistance

## Physical Properties

Coming soon.

• Density
• Suface area
• Surface tension

## Mechanical Properties

Coming soon.

• Viscoelasticity
• Yield and fracture

## Electrical Properties

Coming soon.

• Electrical conductivity
• Dielectric behaviour

## Property Measurement

For methods to obtain material property values, please see the Foundational Methods Documents page:

## Related pages

Introduction to Composites Articles
Foundational Knowledge Articles
Foundational Knowledge Method Documents
Foundational Knowledge Worked Examples
Systems Knowledge Articles
Systems Knowledge Method Documents
Systems Knowledge Worked Examples
Systems Catalogue Articles
Systems Catalogue Objects – Material
Systems Catalogue Objects – Shape
Systems Catalogue Objects – Tooling and consumables
Systems Catalogue Objects – Equipment
Practice Documents
Case Studies
Perspectives Articles

## References

1. [Ref] Callister, William D. (2003). Materials Science and Engineering: An Introduction. John Wiley & Sons, Inc. ISBN 0-471-13576-3.CS1 maint: uses authors parameter (link) CS1 maint: date and year (link)
2. [Ref] Gaskell, David R. (1995). Introduction to the Thermodynamics of Materials. Taylor & Francis. ISBN 1-56032-432-5.CS1 maint: uses authors parameter (link) CS1 maint: date and year (link)
3. [Ref] Fine, L W et al. (2000). Chemistry for Scientists and Engineers. Saunders golden sunburst series. Saunders College Pub. ISBN 9780030312915.CS1 maint: extra punctuation (link) CS1 maint: uses authors parameter (link) CS1 maint: date and year (link)
4. [Ref] Ashby, M.F. (2011). Materials Selection in Mechanical Design. Elsevier. doi:10.1016/c2009-0-25539-5. ISBN 9781856176637.CS1 maint: uses authors parameter (link) CS1 maint: date and year (link)

## Welcome

Welcome to the CKN Knowledge in Practice Centre (KPC). The KPC is a resource for learning and applying scientific knowledge to the practice of composites manufacturing. As you navigate around the KPC, refer back to the information on this right-hand pane as a resource for understanding the intricacies of composites processing and why the KPC is laid out in the way that it is. The following video explains the KPC approach:

## Understanding Composites Processing

The Knowledge in Practice Centre (KPC) is centered around a structured method of thinking about composite material manufacturing. From the top down, the heirarchy consists of:

The way that the material, shape, tooling & consumables and equipment (abbreviated as MSTE) interact with each other during a process step is critical to the outcome of the manufacturing step, and ultimately critical to the quality of the finished part. The interactions between MSTE during a process step can be numerous and complex, but the Knowledge in Practice Centre aims to make you aware of these interactions, understand how one parameter affects another, and understand how to analyze the problem using a systems based approach. Using this approach, the factory can then be developed with a complete understanding and control of all interactions.

## Interrelationship of Function, Shape, Material & Process

Design for manufacturing is critical to ensuring the producibility of a part. Trouble arises when it is considered too late or not at all in the design process. Conversely, process design (controlling the interactions between shape, material, tooling & consumables and equipment to achieve a desired outcome) must always consider the shape and material of the part. Ashby has developed and popularized the approach linking design (function) to the choice of material and shape, which influence the process selected and vice versa, as shown below:

Within the Knowledge in Practice Centre the same methodology is applied but the process is more fully defined by also explicitly calling out the equipment and tooling & consumables. Note that in common usage, a process which consists of many steps can be arbitrarily defined by just one step, e.g. "spray-up". Though convenient, this can be misleading.

## Workflows

The KPC's Practice and Case Study volumes consist of three types of workflows:

• Development - Analyzing the interactions between MSTE in the process steps to make decisions on processing parameters and understanding how the process steps and factory cells fit within the factory.
• Troubleshooting - Guiding you to possible causes of processing issues affecting either cost, rate or quality and directing you to the most appropriate development workflow to improve the process
• Optimization - An expansion on the development workflows where a larger number of options are considered to achieve the best mixture of cost, rate & quality for your application.