Why Controlling Fiber-to-Resin Ratio Matters to Prepreg Production

A high-quality fiberglass prepreg has been engineered to meet exacting standards. It hasn’t been simply thrown together with a haphazard disregard for the customer. A case in point is controlling the fiber-to-resin ratio during production. The ratio cannot be left to chance if a manufacturer is committed to quality.

The fiber-to-resin ratio directly affects a composite material’s quality, performance, and manufacturing efficiency. Anyone who has used low-quality prepregs knows this all too well. Fabricating with a low-quality product produces equally low-quality results. That leads directly to another truth: who you source your fiberglass prepregs from matters.

Optimizing Mechanical Properties

The strength, stiffness, and durability of any composite material are important in the design stage. What we call fiber volume fraction – the ratio of fiber content to resin – impacts all three properties. So the last thing a manufacturer wants is to make the required calculations during the design stage only to wind up with an inferior fiberglass prepreg that does not offer the expected properties.

Fibers provide the reinforcement and mechanical strength, while it is the resin that binds them together and transfers loads among them. So a higher fiber-to-resin ratio generally means enhanced mechanical properties. But it is possible to have too much of a good thing.

Engineers want that optimal balance so they get the desired strength without excess weight. It turns out that excess resin in a fiberglass prepreg can ultimately weaken the finished product. That is bad news as well.

Fabricators Expect Product Consistency

As a fiberglass prepreg supplier, we understand another big reason for controlling the fiber-to-resin ratio: fabricators expect product consistency. Precise control prevents the kind of variation in fiber and resin distribution that drives fabricators crazy. They need consistency in order to be able to depend on mechanical performance. If a prepreg does not offer that, problems are inevitable.

Precise control can be achieved through automation and computer-controlled resin application. The result is a more consistent prepreg from one batch to the next, thereby reducing defects, weaknesses, and voids.

Resin Impacts Handling

Prepregs offer the advantage of not having to manually apply resin during layup. The downside is that fiberglass prepregs can be a bit difficult to handle. As you know, resin content affects a prepreg’s flexibility and tackiness.

Just the right amount of resin allows for the easiest possible cutting, shaping, and layering. If fabricators are dealing with too much resin, they need to fight with prepregs to avoid wrinkles and improper alignment.

On the other hand, too little resin requires fabricators to add more during layup. That is to defeat the purpose of using prepregs to begin with. Prepreg layups are less efficient and not as consistent when additional resin needs to be applied in process.

Achieving the Best Cure and Consolidation

One last consideration is layup curing and consolidation. As a layup cures, its layers adhere to one another to create a laminate for all intents and purposes. A manufacturer does not want those layers to separate. So precise control of the fiber-to-resin ratio is critical.

Resin volume must match polymerization and curing processes to ensure proper lamination. If volume is off even a little bit, increased void content is a concern. Minimizing void content is the key to optimizing durability and fatigue resistance.

Choosing a fiberglass prepreg is a decision that impacts final product quality. So fabricators want and need a prepreg with the ideal fiber-to-resin ratio. The right ratio makes all the difference in the world when it comes to integrity, weight, handling, and curing. When the ratio isn’t quite right, it shows in the results.