What is Prepreg?
What is a Prepreg?
Since most reinforcing fibers are like ropes & yarns, they are generally very strong, stiff, etc., when pulled in the direction of the fibers, but not so much when they are pushed together or flexed. As a result, to maximize the overall performance of the composite material in all directions, it is important to add a matrix (i.e., a glue) to the fibers, so that the fibers become stiff and can carry load when pushed together and when flexed/bent.
This glue/matrix can be added during the part manufacturing process (wet winding, resin transfer molding, etc.), or it can be preimpregnated into the fibers in advance. This type of preimpregnated material is called prepreg, for short.
In the composites industry prepregs are often considered the most advanced system of composite manufacturing. This is because prepregs essentially eliminate process variation issues that can be seen in traditional layups or vacuum infusion processes. In fact, the only elements required to cure (for thermosets) or consolidate (for thermoplastics) the prepreg are heat and pressure. The needed pressure could be applied using a press or autoclave. However, to reduce costs and cycle times, out of autoclave type approaches, such as oven/vacuum consolidation, and in situ and automated processes (such as continuous compression molding, hybrid over molding, and pultrusion, etc.) are becoming more commonplace. Automated lay down techniques such as automated tape laying (ATL), advanced fiber placement (AFP), and 3-D printing techniques are seeing rapid growth.
Advantages of Prepregs
Prepregs provide various advantages for composite fabricators as well as for those who incorporate them in their products. The material itself boasts many features including excellent mechanical properties, lightweight composite design, and a high-quality surface finish. Prepregs also provide excellent benefits during manufacture including:
High repeatability and uniformity:
The process of incorporating prepregs is much simpler and consistent than that of hand layup, wet winding, infusion processing, etc., as both the polymer/resin & fibers are already incorporated in the raw material. Prepregs provide the added benefit of minimizing process variability and the process has less problems relating to part uniformity such as inconsistent finish, excess weight, and inconsistent thickness. Simply put, prepregs can produce high quality products more easily and consistently.
Process simplicity:
Prepregs provide a much simpler and cleaner process from start to finish. Clean ply cuts are easily achievable, and the material can be easily laid into the mold. Prepregs generally have the correct amount of polymer (thermoplastics) or resin and hardener (thermosets) incorporated into the fibers so the lay-up process is much easier and less messy.
Disadvantages of Prepregs
Cost:
Since prepreg manufacturing requires an in-between step, these products are generally more expensive. Wet winding or infusion are generally more cost effective as they remove the need for the interim prepreg impregnation process step.
Shelf life and Storage:
Thermoset prepregs come partially cured and cannot be exposed to excess heat. Heat (even at room temperature) can significantly shorten the shelf life of the product. Consequently, refrigerating or freezing thermoset prepregs during storage is a must. This adds storage and handling costs to the already significant material costs. However, this cost does not exist with thermoplastic prepreg tapes, which can be stored at room temperature indefinitely.
Please reach out to us with your problem that you need help solving. We can help you identify appropriate high-performance composite materials replacing metals or other base materials or to improve your existing composites designs and applications with current state-of-the-art composite materials, automated processes, etc. We are here to help!
Since most reinforcing fibers are like ropes & yarns, they are generally very strong, stiff, etc., when pulled in the direction of the fibers, but not so much when they are pushed together or flexed. As a result, to maximize the overall performance of the composite material in all directions, it is important to add a matrix (i.e., a glue) to the fibers, so that the fibers become stiff and can carry load when pushed together and when flexed/bent.
This glue/matrix can be added during the part manufacturing process (wet winding, resin transfer molding, etc.), or it can be preimpregnated into the fibers in advance. This type of preimpregnated material is called prepreg, for short.
In the composites industry prepregs are often considered the most advanced system of composite manufacturing. This is because prepregs essentially eliminate process variation issues that can be seen in traditional layups or vacuum infusion processes. In fact, the only elements required to cure (for thermosets) or consolidate (for thermoplastics) the prepreg are heat and pressure. The needed pressure could be applied using a press or autoclave. However, to reduce costs and cycle times, out of autoclave type approaches, such as oven/vacuum consolidation, and in situ and automated processes (such as continuous compression molding, hybrid over molding, and pultrusion, etc.) are becoming more commonplace. Automated lay down techniques such as automated tape laying (ATL), advanced fiber placement (AFP), and 3-D printing techniques are seeing rapid growth.
Advantages of Prepregs
Prepregs provide various advantages for composite fabricators as well as for those who incorporate them in their products. The material itself boasts many features including excellent mechanical properties, lightweight composite design, and a high-quality surface finish. Prepregs also provide excellent benefits during manufacture including:
High repeatability and uniformity:
The process of incorporating prepregs is much simpler and consistent than that of hand layup, wet winding, infusion processing, etc., as both the polymer/resin & fibers are already incorporated in the raw material. Prepregs provide the added benefit of minimizing process variability and the process has less problems relating to part uniformity such as inconsistent finish, excess weight, and inconsistent thickness. Simply put, prepregs can produce high quality products more easily and consistently.
Process simplicity:
Prepregs provide a much simpler and cleaner process from start to finish. Clean ply cuts are easily achievable, and the material can be easily laid into the mold. Prepregs generally have the correct amount of polymer (thermoplastics) or resin and hardener (thermosets) incorporated into the fibers so the lay-up process is much easier and less messy.
Disadvantages of Prepregs
Cost:
Since prepreg manufacturing requires an in-between step, these products are generally more expensive. Wet winding or infusion are generally more cost effective as they remove the need for the interim prepreg impregnation process step.
Shelf life and Storage:
Thermoset prepregs come partially cured and cannot be exposed to excess heat. Heat (even at room temperature) can significantly shorten the shelf life of the product. Consequently, refrigerating or freezing thermoset prepregs during storage is a must. This adds storage and handling costs to the already significant material costs. However, this cost does not exist with thermoplastic prepreg tapes, which can be stored at room temperature indefinitely.
Please reach out to us with your problem that you need help solving. We can help you identify appropriate high-performance composite materials replacing metals or other base materials or to improve your existing composites designs and applications with current state-of-the-art composite materials, automated processes, etc. We are here to help!
