Prepreg Lamination

Contents

Introduction
What is CFRP? A Deeper Look at Carbon Fiber Reinforced Plastics
CFRP Molding Methods
- CFRP Molding Methods
Autoclave Molding Method: The Hallmark of High-quality CFRP Product Manufacturing
What are Prepregs?
Prepreg Lamination
Matters of Caution When Laminating
Quasi-isotropic Lamination (Lay-up)
Summary

Introduction

Since our establishment in 1968, Uchida has been pursuing new frontiers in composite (FRP) manufacturing with a focus on leveraging the “strong, lightweight, and non-corrosive” characteristics of CFRP toward next-generational mobility and weight reductions. In this issue, we will discuss prepreg lamination from our perspective as a specialist in the field.

What is CFRP? A Deeper Look at Carbon Fiber Reinforced Plastics

As per the name CFRP (carbon fiber reinforced plastic) is a composite material (type of FRP) whereby a plastic polymer base material is fortified with carbon fibers. The resulting distinctive “lightweight, strong and non-corrosive” qualities has made CFRP a leading material-of-choice across diverse industries and applications.

Carbon fiber itself is a fine yarn-like filament which exhibits exceptional strength but is unable to hold a form on its own. With the product known as CFRP or dry carbon, we composite these strength-obtaining carbon fibers with a plastic polymer to achieve a strong, highly elastic, and formable material.

CFRP Molding Methods

Before delving into CFRP processing, let’s first look at molding methods. There is a wide variety of CFRP molding methods which are selected according to the desired application, shape/form, and production lot.

CFRP Molding Methods

Autoclave Molding

RTM (Resin Transfer Molding)　

Va-RTM (Vacuum Assisted Resin Transfer Molding)

Press Molding

Hand Lay-up Molding

Filament Winding Molding

Sheet Winding Molding

Pultrusion

3D Printer

At Uchida, we use the fabrication methods shown in red.

Autoclave Molding Method: The Hallmark of High-quality CFRP Product Manufacturing

Despite the extensive range of molding methods, autoclave molding remains the hallmark method for design versatility and high-quality CFRP fabrication. High-quality CFRP created from carbon prepregs using the autoclave molding method is known as dry carbon. This method is suitable for prototyping and small-lot production as it does not require expensive metal molds.

The diagram below illustrates the production process of CFRP products using the autoclave molding method.

ASHIDA MFG Co., Ltd.
Autoclave Oven 3
Size : Ø3,000×6,000mm / Operating temperature : at normal temperature – 200℃ / Distribution accuracy : ±2.5℃less / Heating rate : 4.0℃/min. (empty furnace) / Cooling rate : 4.0℃/min. (empty furnace) / Design pressure : 0.99Mpa (maximum working pressure) / Working pressure : 0.7Mpa less (if no specification from the manufacuturer 0.3Mpa around) / Pressure accuracy : ±0.02Mpa（for pressure setting of ０ – 0.99Mpa/cm²） / Boost pressure accuracy : 0 – 0.03Mpa/min / Pressure source : compressed air (regular use) / Vacuum system : back suction system / Vacuum units : 10

What are Prepregs?

The term prepreg refers to a carbon fiber sheet that is pre-impregnated with resin.

Reinforcing carbon fibers that are pre-impregnated with resin prior to curing are typically referred to as carbon prepregs.

Intermediary base material prior to molding (pre-cured)

Prepreg Lamination

Video on carbon prepreg lamination

Matters of Caution When Laminating

・Make sure to remove the protective film and backing paper.

→ Results post-molding defects.

・As an anisotropic material*, lamination of fiber reinforced plastics and CFRPs must strictly follow the design specification, fiber orientation, sequence, and vacuum degassing processes set out in the product design instructions.

→ While appearing identical with the same thickness, the final product will have vastly different mechanical properties.

→ Mistakes in lamination sequence may result in defects and deformations.

・Take care when laminating curved surfaces to prevent the fibers from wrinkling.

→ Cause defects such as uneven or changes in thickness after post-molding.

・Perform lamination in a clean room and take care to prevent any contaminates or foreign objects from mixing between the layers.

→ Lead to defects.

*An anisotropic material is a material whereby the strength of the material is determined by the orientation of the fibers.

Quasi-isotropic Lamination (Lay-up)

As an anisotropic material, carbon fiber reinforced plastics can be designed to exhibit the required strength in the required direction. Quasi-isotropic lamination (lay-up) is technique that orientates the fibers to achieve equal strength in all directions to simulate the isotropic properties seen in metals and other isotropic materials; hence the name quasi-isotropic.

Summary

In this issue, we covered the lamination of prepregs used as intermediate materials in CFRP manufacturing. Hopefully this has given you a clearer insight into the processes and choices involved.

ABOUT UCHIDA - 55 years since our founding

We leverage a wealth of technical expertise as a CFRP molding and processing manufacturer using FRP, GFRP, and CFRP materials. We offer a one-stop solution, encompassing design, analysis, manufacturing, secondary processing, assembly, painting, quality assurance, and testing.

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UCHIDA's equipment

We have cutting-edge equipment to ensure that we can address even the most advanced challenges of our customers.

DMG森精機 - VS1000/40/2050
X軸：2,050mm（ストローク）／ Y軸：1,000mm ／ Z軸：600mm ／テーブル作業面：2,250×1,000mm

ASHIDA MFG Co., Ltd.
Autoclave Oven 2
Size : Ø1,150x1,000mm / Operating temperature : at normal temperature - 400℃ / Design pressure : 2.0Mpa (maximum working pressure) / Vacuum system : back suction system / Vacuum units : 5

ASHIDA MFG Co., Ltd.
Autoclave Oven 3
Size : Ø3,000x6,000mm / Operating temperature : at normal temperature - 200℃ / Distribution accuracy : ±2.5℃less / Heating rate : 4.0℃/min. (empty furnace) / Cooling rate : 4.0℃/min. (empty furnace) / Design pressure : 0.99Mpa (maximum working pressure) / Working pressure : 0.7Mpa less (if no specification from the manufacuturer 0.3Mpa around) / Pressure accuracy : ±0.02Mpa（for pressure setting of ０ - 0.99Mpa/cm²） / Boost pressure accuracy : 0 - 0.03Mpa/min / Pressure source : compressed air (regular use) / Vacuum system : back suction system / Vacuum units : 10

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Oven
Size : W1,000xH1,000xD1,000mm / Temperature range : Environmental Temperature +20 - 300℃ / Temperature elevation capability : Environmental Temperature (20 - 40℃) - 300℃ / 45min less / Vacuum system : back suction system / Vacuum units : 10

ESPEC CORP.
Temperature & Humidity Chamber

INSTRON
Static Universal Testing Machine 5985

Oven
Size : W7,000xH3,000xD2,000mm / Temperature range : Environmental Temperature +20 - 300℃ (Max) / Temperature elevation capability : Environmental Temperature (20 - 40℃) - 300℃ / 60min less / Vacuum system : back suction system / Vacuum units : 10

NEO
X axis : 4,000mm (stroke) / Y axis : 2,000mm / Z axis : 1,200mm / C axis : 0° - ±270° / B axis : 0° - ±110° / Table working place : 4,000x2,000mm

【開発】
3Dプリンター | Markforged

Painting booth
Various painting, and clear finish is done in dedicated painting booth

Adhesion, Finishing, Coating Room
Finishing process, such as trimming, drilling, and bonding, surface treatment of the molded product type and is done in a private booth

Toshiba Matrixeye EX (Ultrasonic flaw detector)
Matrix-Arrey : 32

AMETEK CREAFORM Metra
SCAN750 Elite (3D scan)

Olympus Corp.
Inverted Microscopes

Oven
Size : W450xH450xD450mm / Temperature range : Environmental Temperature +20 - 650℃ / Temperature elevation capability : Environmental Temperature+50 - 650℃/120min less

Cutting Plotter Table working place : W1,500xL3,500mm

SHIMA SEIKI MFG., LTD
Cutting Plotter

KUKA
Robot

Krauss Maffei
Epoxy resin injection machine Resin 60L ／ Hardener 25L

Krauss Maffei
630t Press machine Height total 5,200mm ／ Length max 1,500mm ／ Width max 1,200mm ／ Whole cycle time per component part 240sec

DMG森精機 - NV5000B/40
X軸：1,020mm（ストローク）／ Y軸：510mm ／ Z軸：510mm ／テーブル作業面：1,320×600mm

Big sized clean room
JIS B 9920 cleanliness class maximum concentration (Pcs/m³） / Class 5 : 100,000m³ / Capacity : m² (16,000x16,000mm) 760m² (16,000x16,000x3,000mm) / Temperature and humidity condition : Temperature : 23℃±3℃, Humidity 65% less / Ambient conditions : Temperature 35℃ during summer, Humidity 70% less / Ambient conditions : Temperature 35℃ during summer, Humidity 70% less / Temperature -5℃ during winter, Humidity 40% less