How Prepregs are Used

Contents

Introduction
What is CFRP? A Deeper Look at Carbon Fiber Reinforced Plastics
What are Prepregs?
Prepreg Storage
Prepreg Lamination (Lay-up)
Matters of Caution When Laminating
Quasi-isotropic Lamination (Lay-up)
Post Lamination Vacuum Bagging: “Bagging”
Autoclave Molding (Curing)
Summary

Introduction

At Uchida, we pride ourselves on leveraging CFRP and its “strong, lightweight, and non-corrosive” properties toward next-generation mobility and weight reduction. In this issue, we will take you on a tour of the uses of prepregs from our perspective, as a company specializing in FRP molding since our establishment in 1968.

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.

What are Prepregs?

Prepreg is a common term for a reinforcing material that is pre-impregnated with resin for use in manufacturing composites. The term carbon prepreg simply refers to a prepreg that utilizes carbon fiber as the reinforcing material.

Prepregs are intermediate materials in an uncured state.

The main forms of carbon fiber are a woven cloth type (Cloth) or uni-directional (UD), whereby the fibers are aligned in the same direction.

Prepreg Storage

Prepregs are intermediate materials pre-impregnated, generally, with thermosetting resins such as epoxies. To avoid premature hardening, which would render the resin unstable, they are typically stored in temperatures of -18℃ or below.

Prepreg Lamination (Lay-up)

Prepreg lamination must be performed in a temperature-controlled clean room. If done in high temperature or humidity environments, the prepregs will absorb the humidity leading to post-molding defects.

Next, we laminate the carbon prepregs.

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.

Post Lamination Vacuum Bagging: “Bagging”

After lamination completion, we apply the auxiliary materials and place the entire preform (lay-up) into a vacuum bag and seal it. This process is referred to as vacuum-bagging, or bagging.

Autoclave Molding (Curing)

Once bagged we insert the preform into the autoclave and commence the curing process.

Summary

In this issue, we looked at how we use intermediary prepreg materials for CFRP manufacturing, in the hope of providing you with a better understanding of the entire process.

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