Reference - Separating sources of manufacturing distortion in laminated composites
| Type | Journal |
|---|---|
| Title | Separating sources of manufacturing distortion in laminated composites |
| Abstract | Manufacturing distortion in composites has been a problem for many years and continues to impede the development of composite materials. Previous efforts have shown these manufacturing distortions to be related to differences in the in-plane and through-thickness properties. Often tooling is modified in an attempt to compensate for these fabrication induced distortions; however, the various sources of the problem have not been clearly identified, measured, nor accepted. Earlier efforts have suggested that both the cooldown from process temperature and shrinkage during cure play a role, yet no single work has measured the relative contributions of these effects. Further, researchers have suggested numerous other factors as being responsible for all, or some portion, of the measured distortion. In this work, distortion in autoclave-cured laminated composites has been experimentally measured, at temperatures ranging from 24°C to 178°C, to determine the reversible and irreversible contributions to manufacturing warpage and to attempt to separate the distortion into components related to different mechanisms. Three mechanisms, anisotropy, material property gradients, and stress gradients are described, and are further separated into thermoelastic and non-thermoelastic components. The measured reversible response closely matches computed distortion, based solely on the in-plane and through-thickness coefficients of thermal expansion. Further, it seems that the irreversible contributions can be separated into material dependent effects, such as cure shrinkage, and process related effects, such as part/tool interactions. Calculations, based on anisotropy, indicate that both temperature change and cure shrinkage contribute significantly to a manufacturing distortion; but, their contribution does not account for the total distortion. The irreversible contribution is much greater than predicted, indicating the action of a mechanism which only involves a non-thermoelastic contribution, such as a part/tool interaction. Trends in the experimentally observed distortion indicate the presence of other non-thermoelastic process related contributions and show that these other contributions seem to diminish as the thickness, corner radius and included angle increase. |
| Authors |
|
| Date | 2000 |
| Issue | 8 |
| Pages | 621-641 |
| Journal | Journal of Reinforced Plastics and Composites |
| Volume | 19 |
| DOI | 10.1106/CRMP-ARE5-GVPP-0Y7N |
| ISSN | 07316844 |
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.
