Processing science - A151
| Processing science | |
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| Foundational knowledge article | |
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| Document Type | Article |
| Document Identifier | 151 |
| Themes | |
| Tags | |
Overview[edit | edit source]
A unique aspect for polymer matrix composites (PMC) is that the material itself is concurrently made during the part manufacturing process. During processing, the matrix material (polymer) and reinforcement (fibre) combine together forming the resulting composite material. For the polymer matrix, changes in physical state take place in order for the part to be set into shape. For thermoset polymers, additional chemical state changes are also occurring during this process.
The composites manufacturing itself process can be broken down into the following processing themes – each with various aspects of material evolution taking place:
- State variables for processing
- Thermal behaviour
- Material deposition/flow and consolidation behaviour
- Stress deformation behaviour
State variables for processing[edit | edit source]
Link to main State Variables for Processing page
In the processing of polymer matrix composites (PMC), a fundamental set of state variables define the current state of the material system as the material evolves during the manufacturing process.
For example, for a uni-directional reinforced polymer matrix material, the three most basic state variables are:
- \(x\): degree of cure
- \(T\): temperature
- \(V_f\): fibre volume fraction
From the above list, all other material properties are dependent on \(x\), \(T\) and \(V_f\):
- Mechanical properties\(_{(x,T,V_f)}\) - e.g. viscosity, modulus
- Physical properties\(_{(x,T,V_f)}\) - e.g. thermal expansion, cure shrinkage
- Thermal properties\(_{(x,T,V_f)}\) - e.g. thermal conductivity, density, specific heat
The state variable list is complete when one can predict the future response of the material system based on the material's current state independent of prior process history/path. Additional state variables may also be required depending on the material system being described. For fabric reinforcement, additional variables necessary include orientation (θ), porosity (\(V_v\)), etc.
Thermal behaviour[edit | edit source]
Link to main Thermal Behaviour page
Thermal behaviour is one of the key KPC themes involved in the composite manufacturing process. The related pages in the foundational knowledge volumes provide KPC users an understanding of the thermal topics that drive the processing science in the manufacturing of composite materials.
The foundational knowledge volume contains pages for the following thermal behaviour topics:
- Basics of heat transfer
- Thermal phase transformation of polymers
- Curing of thermosetting polymers
- Melt and crystallization of thermoplastic polymers
- Chemical degradation of polymers
- Physical aging of polymers
Click here to explore the thermal behaviour topics.
Material deposition/flow and consolidation behaviour[edit | edit source]
Link to main Material Deposition/Flow and Consolidation Behavious page
Material deposition and flow and consolidation behaviour involves the process(es) in which the reinforcement and matrix constituents come together in the composite shape forming process. These steps are generally considered as the different composite manufacturing processes (click here to read more about some common process examples).
The basic topics within this processing theme include:
- Dry fabric forming
- Infusion
- Prepreg forming
- Automated fibre placement (AFP)
Stress-deformation behaviour[edit | edit source]
Link to main Stress-Deformation Behaviour page
Stress-deformation behaviour, and in particular residual stress development, occurs at many length scales in a composite structure. At the microscale, phase-level residual stresses accumulate due to the mismatch between thermal expansion of resin and fiber, as well as the resin cure/crystallization shrinkage. At the mesoscale, ply-level residual stresses accumulate due to mismatch between the layers in the laminate. Finally, at the macroscale, contributors to residual stress include geometric features and constraints, thermal and cure gradients, volume fraction variations due to resin flow, interaction between components in an assembly, tool part interaction, and machining.
Explore this area further
Related pages
| Page type | Links |
|---|---|
| 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 |
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| About | Help |
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 factory
- Factory cells and/or the factory layout
- Process steps (embodied in the factory process flow) consisting 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.
