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Reference - Aspects of Flow and Compaction of Laminated Composites Shapes During Cure

From CKN Knowledge in Practice Centre
Type Thesis
Title Aspects of Flow and Compaction of Laminated Composites Shapes During Cure
Abstract [[Abstract::Cost-effective manufacturing has become the primary objective for many industries using composite materials in primary structures. To realize this objective, it is often desired to use process modelling, as it helps understand the interaction between the parameters affecting the product quality. Among the multitude of phenomena occurring during composites processing, resin flow is a critical issue. It affects the fibre volume fraction distribution, the mechanical properties of the laminate and the final dimensions of the part. For thermoset matrix composites, the percolation flow approach is typically used to model flow and compaction. In this approach, the resin flows relative to the fibres and the flow has to be coupled with the fibre bed compaction behaviour to obtain the final shape of the laminate. In the present work, a percolation flow-compaction model is implemented in a two-dimensional finite element processing model for complex shapes such as angles or hat sections. Material properties required for the flow-compaction model, such as resin viscosity and the fibre bed compaction curve are measured for two carbon-epoxy composites: AS4/3501-6 and AS4/8552. An experimental technique to measure the fibre bed compaction curve directly from the prepreg is presented. The fibre bed compaction curves are validated with results from uniaxial compaction tests. The flow-compaction model is used to study the effect of a variation of the material properties on the compaction of angle laminates. The results from this sensitivity analysis show that the compaction curve significantly affects the final laminate thickness while the fibre bed shear modulus controls the ability of the fibres to conform to a curvilinear shape. A series of angle laminates were cured to study the effect of fibre orientation, bagging conditions, material and tool type on compaction behaviour. Simulations of the angle laminates in bleed conditions are in good agreement with the experiments. However, the model does not predict the experimentally observed magnitude of the deformation at the corner of the [90°] layup. This behaviour is attributed to shear flow, where the fibres and the resin move together as a very viscous anisotropic fluid. Direct observations of the compaction behaviour during transverse flow are presented. They confirm the kinematic relations used in shear flow theory and show that friction is present at the plate-laminate interface. Next, the conditions required to produce percolation or shear flow are investigated in a simple uniaxial compaction experiment. Fibre orientation and resin viscosity are the primary variables determining the dominant flow mechanism. Shear flow is primarily affected by the fibre orientation and occurs essentially in the direction perpendicular to the fibres. Percolation flow depends on the resin viscosity and occurs mainly in the direction where shear flow is not possible.]]
  • Hubert, Pascal
City Vancouver
Department Metals and Materials Engineering
Date 1996
University The University of British Columbia, Vancouver
Publication UBC Open Collections
DOI 10.14288/1.0078499
Country Canada
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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.

The relationship between material, shape, tooling & consumables and equipment during a process step

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:

The relationship between function, material, shape and process

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.

The relationship between function, material, shape and process consisting of Equipment and Tooling and consumables


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.