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Practice for Developing a Consolidation Step - P158

From CKN Knowledge in Practice Centre
Practice for Developing a Consolidation Step
Practice document
Compaction Cell-Dsp5DErqCN9K.svg
Document Type Practice
Document Identifier 158
Objective functions
MSTE workflow Development

Overview[edit | edit source]

This page will guide the user in developing their consolidation step. Firstly highlighting some of the options to consider when selecting a type of consolidation method, then providing practice documents that describe different processes in detail. This includes conceptual screening and preliminary selection of temperature and pressure, then detailed finalization of the manufacturing (MSTE) system as a whole. The page is broken into three tabs that cover these activities.

Introduction[edit | edit source]

Consolidation refers to compacting the fibre bed and resin of a composite material system in order to achieve a desirable fibre volume fraction, and reduce/avoid gaps in the the laminate. This step contributes to the final part strength, durability, and dimensional accuracy. While a consolidation step offers numerous benefits in terms of composite part quality and performance, it is not always mandatory. The decision to implement this or not depends on the specific requirements of the application, the chosen manufacturing process, available equipment, and the desired properties of the final composite part.

Significance[edit | edit source]

The consolidation process serves several critical functions in shaping the properties of a composite part. To begin with, its primary objective is to eliminate trapped air between the layers of the material, whether it's between Prepreg layers or dry fibers (read more about Porosity). Effective consolidation further enhances the fiber volume fraction by ensuring the proper compaction of fiber and the even distribution of the matrix material. Throughout the manufacturing process, the continuous application of pressure to the material system also aids in preventing the formation of porosity. Lastly, consolidation plays a key role in achieving a smoother and more consistent surface finish for the final part.

Read more about Materials deposition and consolidation management (MDCM).

Practice[edit | edit source]

The following section follows the three process design gates of screening, selecting, and finalizing. Each of the process design gates are discussed under the consideration of each of the MSTE topics. Each MSTE topic provides questions to consider for each design gate to further advance each topic from screen to finalize.

Material[edit | edit source]

The choice of fibre and resin system is going to have an effect on how the layup will consolidate. Different fibre types and architectures have different properties (Fibre Architecture: Availability, pros and cons, and selection for my application), which can affect the way they behave when pressure is applied. For the resin system, consolidation needs to be considered when applying pressure, but also during curing. Room temperature cure or oven/autoclave cure? If it is a room temperature cure, are you applying manual pressure to the part and is that enough, or do you need a vacuum bag?

If it is an oven or autoclave cure, will there be a vacuum bag over it during cure? Is that enough to consolidate all the plies and resin, or will you need a Debulking step during layup?

Fibre orientation is critical to the final properties of the part. When performing an infusion or resin transfer moulding process, there is a risk of resin flow disturbing the fibre if there is not enough consolidation pressure to hold them in place.

  • Is there a need for a debulk before infusing the resin?
  • Will special precautions be made so the incoming resin does not move the fibre?
  • Is the resin viscosity suitable or should it be lower?

This is also true for wet layups and prepreg layups. Using a Debulking step can aid in compacting the fibre and prevent movement.

The tackiness or stickiness of the material can affect how it is handled and laid up. Some materials may require the use of release films or peel plies to prevent the material from sticking to the tools or itself during consolidation.

Achieving the correct resin-to-fiber ratio is critical for composite performance. Proper consolidation ensures that the resin wets out the fiber evenly, avoiding resin-rich or resin-poor areas in the final part. Pre-bleeding is when resin is intentionally removed from the part under vacuum through a bleeder cloth.

If your material is a thermoplastic, consolidation must happen at temperatures above the melt temperature for semi-crystalline materials. The general rule of thumb is to apply pressure to the part at temperatures of 90°C or less above the melting temperature[1]. Keeping in mind that the pressures and temperatures required for thermoplastic processing are higher than traditional thermosets. It is also important to consider the time the material will need to consolidate as powder coated comingled prepregs require time to fully consolidate, hot-melt prepregs can consolidate in a very short amount of time. To achieve a well consolidated thermoplastic part, the pressure must remain applied when the part is cooling until the temperature is below Tg. This inhibits the formation of voids, prevents elastic recovery in the fibres and maintains the desired shape of the part[1]. Read more at Consolidation of Thermoplastics.

See also A267

Shape[edit | edit source]

For complicated tooling and geometries, it is important to consider if the pressure applied to the part will be uniform. Parts with varying curves and contours may require different consolidation methods to ensure that the composite material conforms to the shape without wrinkles, voids, or excessive resin pooling. Is it worth it to develop a caul plate? Is there enough space on the tool for a vacuum bag to be applied? Can a bladder be used?

If the part is complex, there may be a need to perform a hot-debulking step or a pre-bleeding step when using prepreg. Hot debulking is applying vacuum to a part as well as heat, 65°C to 90°C typically [1].

Parts with varying thicknesses may experience consolidation challenges. Thicker areas may require longer consolidation times or higher pressure to achieve the desired compaction, while thinner areas may be more susceptible to over-compression.

See also A268

Equipment[edit | edit source]

For automated processes such as A300 and A303 will there be enough pressure applied from the machines to ensure enough consolidation of the fibre bed?

Does the facility have integrated vacuum lines, or will vacuum pumps need to be purchased for this manufacturing process?

See also A269

Tooling & Consumables[edit | edit source]

Injection moulding and compression moulding provide very high and consistent pressures for consolidation. However, the infrastructure is expensive and the part geometry is limited.

For a vacuum bagged part, will you need an edge dam? Is there enough room on your tool to apply a vacuum bag? Is it worth it to invest in a reusable silicone vacuum bag for high volume parts?

The consolidation process often involves the application of pressure and, in some cases, vacuum. The amount and distribution of pressure or vacuum should be carefully controlled to avoid wrinkles, voids, or excessive resin flow.

See also A270

Read Select for the next step.

Correct temperature and pressure are important to consolidate the material. Will the correct temperature be reached without an oven? Will the correct pressure be reached without an Autoclave? For every parameter that needs to be controlled by specialized equipment like an autoclave, the cost of equipment will increase rapidly. See also Room temperature transformation.

To achieve high rates in consolidation processes, pre-shaped material or pre-made vacuum application methods will increase the rate, but usually add to the cost as well. For example, using disposable vacuum bags for curing and debulking allows for variable parts and shapes at a fairly low cost. Switching to reusable vacuum bags will limit part shapes and increase cost, but will reduce the time spent on making vacuum bags per part.

Aiming for higher production rates can lead to the decline of quality. For example, a reduction of dwell time can lead to less time available for the material to undergo complete consolidation. Inadequate dwell time can result in insufficient compaction, causing voids, wrinkles, or incomplete curing. Quality can also be affected by rushing to perform tasks, this can lead to misalignment or damage to the material, affecting the consolidation quality.

Consolidation can be a very energy intensive process, so it is important to keep in mind the emission effects that come from energy hungry equipment. Optimizing cure cycles and consolidation times can minimize energy use while maintaining product quality, see Production Optimization for optimization strategies. Other strategies may include heat recovery from heated processes, or reusable vacuum bags.

Some considerations to review at this stage:

  • Is there enough room on your tool to apply a vacuum bag?
  • Is it worth it to invest in a reusable silicone vacuum bag for high volume parts?
  • If the desired production rate is very high, is it worth it to invest in compression moulding equipment?
  • Will this method of debulking slow down production rate?
  • For a thermoplastic part, will there be a need for pre-consolidation and pre heating? if so, will the plies need to be tacked together to prevent them from moving beforehand?

Read Finalize for the next step.

Prototyping a few parts with slight variations of the consolidation steps will help eliminate and determine what is necessary. At this stage it will be valuable to measure porosity and the fibre volume fraction obtained in the part in order to determine how successful the consolidation of the part has been. A low amount of porosity will suggest that there has been adequate pressure and gas transport though the part. A high fibre volume fraction will indicate a high consolidation pressure on the part. Other measurements and tests may be necessary as well, for example confirming the profile and shape of the part is as it should be and that the fibres themselves have not been shifted during cure.

Read more about Porosity and How to measure reinforcement content (and corresponding matrix content). As well as Effect of consolidation in residual stress management

Consolidation During Deposition[edit | edit source]

Consolidation for Cure[edit | edit source]

Thermoplastic Consolidation[edit | edit source]

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


  1. 1.0 1.1 1.2 [Ref] Campbell, F.C. (2004). Manufacturing Processes for Advanced Composites. Elsevier. doi:10.1016/B978-1-85617-415-2.X5000-X. ISBN 9781856174152.CS1 maint: uses authors parameter (link) CS1 maint: date and year (link)

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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

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


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