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Choosing Your Layup Process - Prepreg vs Traditional

Mar 25th 2021

Murphy's Law: a law of nature, anything that can go wrong, will go wrong. Especially true in composite fabrication as variables are always going to exist. Between tooling, plycut, layup, bagging, cure, demold, and trim, creating or manufacturing a quality composite is no simple task. Prepreg material can be a great option when things look like they are getting way too complicated.

Explanation of Benefits of Using Prepreg Material over Traditional Layup Techniques:

A prepreg material is a pre-impregnated mixture of uncured resin and fabric that will make a composite laminate. Prepreg material design is to have an ideal ratio of fabric to resin. This resin ratio provides the cured composite's concise properties such as UTS (ultimate tensile strength) and Modulus (Applied Stress vs. Material Strain). This ratio eliminates variables due to the traditional hand layup's likeliness to variate this resin ratio, consequently altering final composite properties. Giving that the prepreg material and resin to fiber ratio will be consistent ensures better laminate properties.

Variation in ply cutting & layup is mitigated (or limited) by the quality of the prepreg material. Reputable prepreg material manufacturers undergo extensive in-house processing and visual testing to ensure to the customer that material will have a uniform application of resin throughout the fibers. Uniformity of the material translates to layup as the parts' final thickness will be consistent and the process made repeatable. When planning to manufacture or make multiple parts, prepreg materials provide a considerable advantage.

Cleanliness, when using prepreg material, significantly increases. Eliminated are the problems of rollers, cups, mixing tools, and resin buckets getting in the way and placing the focus on the details. This focus will provide the future composite laminate with a patient layup and bagging process. Prepreg material will also mitigate the waste of resin and fabric material caused by traditional layup methods.

Prepreg materials provide peace of mind during layup as the resin cures by heat and pressure rather than solely on time. Giving time to properly bag or work through any sudden issues is vital during any layup. Using a prepreg material provides an advantage over fighting the setup time of the resin. The surface finish of a composite part is also easily achieved relative to traditional hand layups.

When debating on what process to go with, whether it be a traditional layup, using prepreg, or infusion, it is essential to ask the following questions before coming to a decision:

What quantity of parts for fabricating needs to be considered?

If making a single part for anything fabricated, using a prepreg material may not make economic sense. The advantages of prepreg materials lie in producing 20-30 to even hundreds of parts. Using traditional layup techniques may be more feasible when making only a single part or if the mold requires future modifications due to design changes. Notably important is that advanced planning will significantly reduce the mess that traditional layups bring.

What is the complexity of the contours of the part?

When planning a layup that goes over multiple changing angles in a tool, it is vital to understand the workability of prepreg material is greater than that of traditional methods. However, for simple contours, traditional layups would suffice for many situations.

Have questions on what would be the best layup process for your project & if Prepreg is the right way to go? Contact us here at Composite Envisions, and we’ll be happy to help and set you on the correct path.