System interactions - A109
| System interactions | |
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| Systems knowledge article | |
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| System representation of a composite processing step. | |
| Document Type | Article |
| Document Identifier | 109 |
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| Prerequisites | |
Overview[edit | edit source]
In composites manufacturing, each process occuring in the factory can thought of as a system of interactions between the part, tooling and consumables (T), and equipment (E)[1]. The part can be further broken into its constituent materials (M) and shape or geometry (S). In shorthand notation, this is collectively referred to as the MSTE system. The interactions between these components are what determine the outcomes of a given process step, such as final degree of cure (DOC) or porosity. These interactions are based on foundational science principles. In many cases, it is convenient to represent the system components as a simple resistance diagram. Take a heating scenario as depicted in the image on the right for example. In this schematic, the part - divided into material (M) and shape (S) - and tool (T) are represented by spring elements, each with their own thermal properties; while, E represents the environmental conditions of the equipment. Depending on the assembly, there may be multiple material systems in play, or the part may be surrounded by tooling on two sides (in a closed mould process for example). Moreover, if the consumables add significant thermal resistance to the process then they too should be considered and represented in the diagram (for example breather cloth in a vacuum bag assembly). In any case, representing the system as a series of elements with individual material properties under a given set of environmental conditions is a good way to deconstruct the problem.
Single interaction[edit | edit source]
At the simplest level, one system class interacts with one other system class. There are four practical and useful interactions to understand. They are described below.
Interaction between material and shape (MS)[edit | edit source]
The material and shape together form the part. Therefore, the interaction between material and shape defines the outcome sensitivity for the system. That is, how the part will respond to the imposed boundary conditions. The part response is based on the physical dimensions and construction of the part as well as its material properties. The state of the part is what determines the final outcomes for the system.
Interaction between the tooling and equipment (TE)[edit | edit source]
The interaction between tooling and equipment defines the system boundary conditions with respect to the part. Within any given cell, the equipment impose the environmental conditions that all other elements of the system assembly are subject to. The energy imposed by the equipment either interfaces directly with the part or indirectly by interfacing with the tooling/consumables adjacent to the part. For example, the temperature of a part in an oven is dependent on the interaction between the thermal conditions of the oven and the exposed surfaces of the part and/or between the thermal conditions of any tooling/consumables the part is in contact with. The latter scenario is significant, as during processing of composite materials there is almost always some form of tooling or consumable involved in the assembly which greatly affects heat transfer to and from the part. The thermal conditions of the tooling and consumables are themselves directly dependent on their interaction with the equipment.
Interaction between shape and tool (ST)[edit | edit source]
The interaction between shape and tool define the dimensions of the tool-part assembly. This is useful from the perspective of understanding how impinging airflow may be redirected in a thermal system. Moreover, the geometry of the tool-part assembly must be considered when selecting equipment.
Interaction between the material and equipment (ME)[edit | edit source]
It is necessary that the part achieves its specifications as defined for the material system. Therefore, at a minimum, the equipment on its own should be able to provide the environmental conditions necessary to satisfy the material specs. Consider a thermal system. An empty piece of equipment (such as an oven) represents the best case scenario for achieving the thermal specifications of the material. For example, if a material must be processed at 180°C, it requires a heating environment that can achieve such a temperature. As soon as the tooling and part(s) are added, thermal resistances are introduced to the system, and the part may not achieve the intended thermal history. This method of thinking breaks down for thermosetting resins at low environmental temperatures, where the heat of reaction is considerably higher than the heat of the environment. Here, it is the exothermic nature of the material that drives the cure reaction, not the thermal conditions imposed by the equipment; although the ambient air temperature does play an important role. In either case, these interactions are important considerations when sourcing equipment and defining the manufacturing process.
Multiple interactions[edit | edit source]
In reality, within any given factory cell, multiple system classes interact with one another. The manner in which they interact is a combination of the single interactions listed above.
Interaction between material, shape, and tooling (MST)[edit | edit source]
The material and shape together form the part. The interaction between tool and part defines how energy transfers through the tooling and consumables into the part and vice versa. In the case of thermal management it is the transfer of heat to and from the tool-part interface that is important. Changing the geometry or the materials of either tool or part will affect the transfer of energy between the two. In some cases, changing the tooling parameters may result in dramatically different outcomes for the part. This can be used to tailor the system design and, if not considered, may lead to unexpected failures. In the case of residual stress and dimensional control management, tool-part interaction is a common subject in composite processing literature. Here, the transfer of energy between tool and part occurs mechanically as the tool and part expand and contract differently under temperature, imposing stresses across the tool-part interface.
Interaction between shape, tool, and equipment (STE)[edit | edit source]
As mentioned above, the interaction between shape and tooling define the physical dimensions of the tool-part assembly. When considered with equipment, the STE interaction represents the geometry of the entire system. Part shape, tooling dimensions, and equipment specifications must be considered together when qualifying the system. If the equipment is relatively small compared to the tool-part assembly, then a batch-load of several tools/parts may not be possible. Moreover, a large tool/part may block or redirect airflow around other tools/parts in a convective heating environment. Similarly, the local geometry of a given tool-part assembly may influence airflow across its own surface. All of this, in turn, changes the local heat transfer coefficient (HTC) across the part surface(s).
Interaction between material, shape, tooling, and equipment (MSTE)[edit | edit source]
The interaction between M, S, T, and E captures the entire system response, including the boundary conditions of the tool-part assembly, and the internal energy transfer to and from the part. In order to understand the outcomes of a system, all MSTE interactions must be considered. In order to approach this, it is easiest to consider the individual contributions each class makes to the system and how they come together in the manner described above. The individual contributions of each system class are explored in detail in further pages for each of the processing themes.
For thermal management related interactions refer to the following pages:
- Effect of material in a thermal management system
- Effect of shape in a thermal management system
- Effect of tooling in a thermal management system
- Effect of equipment in a thermal management system
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 |
References
- ↑ [Ref] Fabris, Janna Noemi (2018). A Framework for Formalizing Science Based Composites Manufacturing Practice (Thesis). The University of British Columbia, Vancouver. doi:10.14288/1.0372787.CS1 maint: uses authors parameter (link)
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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.
