“Intelligent Design” of Vacuum Infusion Technology in Europe and America

 

What is the Concept of Maximizing Fiber and Resin Content?

 

What is the Significance of this Concept for Composite Materials?

 

Composite materials are widely used mainly because of their relative advantages in strength and weight. This advantage is mainly achieved by maximizing the relative ratio of fiber to resin.

 

Simply put, how to make the fiber reinforcement in the part just completely impregnated with resin, or in the process of part production, try to make the excess content in the part as low as possible except for the necessary resin to completely impregnate the fiber reinforcement. 60% resin content is generally considered to be a good value in the industry.

 

Dry areas are often more fragile than areas with too high resin content. How to maximize the fiber and resin content is often closely related to the level of the process operator himself.

 

Evolution of Vacuum Infusion Process

Traditional hand lay-up process → vacuum bagging → vacuum infusion

 

Advantages Of Vacuum Bagging Process Over Hand Lay-Up Process:

* Extract the gas trapped between the layers

* Further compress the fiber layer to promote effective mechanical conduction between the fiber bundles and prevent the change of fiber direction during the curing process of the part

* Reduce the moisture content in the part

* Optimize the content of fiber and resin in the part

* Improve the mechanical properties of the part

* “Slim down” the part

 

Advantages Of Vacuum Infusion Over Vacuum Bagging Process:

* More optimized fiber and resin ratio (low porosity) (the thickness of the fabric product with the same weight per square meter is smaller than that of hand lay-up)

* Less Resin Waste

* More Stable Resin Usage

* More Sufficient Process Preparation time

* Cleaner Operation Process

 

Links and Key Points of Vacuum Infusion Process

Link:

preparation before infusion-resin introduction-further testing (cycle and continuous improvement process)

 

Key Points of Vacuum Infusion Process:

mold-resin and fiber-vacuum system (vacuum pipeline-vacuum bag-vacuum pump)-resin infusion

 

Mold Requirements:

The mold frame should preferably be 15-16 cm wide, the mold should have a high-gloss surface quality, and the mold should have good sealing

 

Resin Selection

(typical viscosity is 100-200 CPS, non-thixotropic, because thixotropy will cause the resin to flow too slowly):

 

Selection of Fiber Reinforcement for Vacuum Infusion:

* Glass fiber (the looser the weave, the more conducive to resin flow), continuous mat in non-woven mat is more conducive to resin flow than chopped mat (the binder contained in chopped mat will hinder resin flow); combining continuous mat with unidirectional glass fabric will promote resin flow

 

* Carbon Fiber and Aramid Fiber Fabrics have worse resin conductivity than glass fiber fabrics, so the infusion mesh is often used for shaping by spraying glue.

 

Vacuum System

* Key points of vacuum pump: If complete vacuum cannot be achieved within 5-8 minutes, the vacuum pump used may be too small. Before sealing the vacuum bag and turning on the vacuum pump, the air in the bag must be squeezed out as much as possible. This practice can effectively reduce the working time required for the vacuum pump to achieve full vacuum in the bag.

 

Resin Diversion

 

Three Main Factors Affecting Resin Flow

 

* Wetting of reinforcement (reinforcements with multi-axial or wrinkle-free weaving patterns are conducive to resin flow)

 

* Resin viscosity (too low is not a good thing, excessive styrene will cause poor viscosity between the fiber sizing agent and the resin contact surface, and the loss is too fast. By adjusting the resin gel time, the surface quality of the part may be affected)

 

* Pressure difference between the inside and outside of the mold cavity (use vacuum side leakage instruments (ultrasonic leak detectors and professional large leak detectors) to check vacuum leak points)

 

Precautions for Resin Introduction and Vacuum Exhaust port

It is best to have extensions for the injection port and the exhaust port, so that the resin and the exhaust port can be carried out at multiple points

 

 

Guide Medium

When the resin enters the mold cavity from the pre-set inlet, the flow direction of the resin tends to be in the direction of low resistance, and the material resistance of the reinforcement itself will have a great impact on the flow direction of the resin; the guide material included in the product structure design can be divided into simple guide material (non-continuous fast guide nylon felt and sandwich material with better synchronization, such as SORIC felt-thickness loss within 10% under vacuum compression); structural foam guide material (grooving or punching to promote resin flow); in addition, the surface guide material located on the surface of the product during the production process and needs to be peeled off after demolding (spiral tubes and guide nets are included in this category; such guide media can be fixed in the product or mold cavity with sealing strips; such materials can effectively help the resin flow quickly to various parts of the mold cavity and prevent the formation of resin dry areas) “Intelligent design” of vacuum induction process in Europe and the United States

 

Simulation Software

Although the vacuum induction process has many advantages, it also has defects such as complex process preparation, easy scrapping, and the need for continuous trial and optimization.

 

Therefore, Europe and the United States have been committed to the development of related process design software, For example: POLYWORX’s RTM-WORX process simulation software.

 

More Stable and Simple Vacuum System

 

 

A More Cleverly Designed Diversion Net

 

 

New Omega Resin Drainage Tube

 

 

Advantages Of Use:

* Compared with traditional OMEGA tubes, the appearance of indentations is greatly reduced

* It can effectively lock the bubbles mixed in the resin to prevent them from flowing into the product structure

* The surface of the product is smoother and the structural strength is higher

* Easy to operate

* Effectively control manufacturing costs and shorten molding time

 

Intelligent Vacuum Ventilation Tube

 

 

The use of this technology can ensure that the parts in the mold cavity have a more uniform resin infiltration rate, and greatly reduce the occurrence of bubbles, pinholes, and dry spots that affect the final mechanical strength and surface quality of the parts.

 

Its working principle is mainly to discharge the air in the mold cavity during the production process and the volatiles released during the curing process of the resin gel through the unique microporous membrane attached to the spiral hose, and ensure that there is enough vacuum-injected resin in the mold cavity to meet the requirements of product design.

 

 

Resin Introduction Automatic Control Valve

 

 

Its working principle is to sense the change of relative pressure inside and outside the bag in real time through the automatic control valve connected to the injection pipe, and make corresponding valve closing adjustments to achieve the best injection effect.

 

When the fiber part of the component is completely and evenly infiltrated, the valve will close automatically, which will also avoid the need for manual monitoring of the resin introduction status in traditional processes.

 

In the future, composite material manufacturers using vacuum resin introduction technology are expected to solve problems that are prone to occur in traditional processes, such as excessive resin content at the injection port, uneven component infiltration, inability to achieve optimal fiber content, poor quality stability, complicated process operations and low efficiency through the use of this product.

 

 

Technical Advantages

*Automatically Regulate the Resin Introduction Rate

*Avoid the Phenomenon of Resin Accumulation at the Resin Injection Port

*Ensure Uniform Infiltration of Fiber Fabrics

*Optimize the Fiber Content of the Product

*Guaranteed Product Quality Stability