The use of plastic reinforcements in thermosets, polyesters, and epoxies has been greatly enhanced by the addition of fiber reinforcements that improve their mechanical properties and heat resistance. These fiber reinforcements can take the form of glass mats, fabrics, unidirectional fibers, and biaxial fibers, which are impregnated with liquid resin and then cured to form a bond that is highly dependent on the type of glass fibers used, the length of the fibers, the number of fibers, and their orientation.

As a result of this process, composite materials are created that exhibit exceptional mechanical strength while remaining lightweight..

Of all the available options, glass fiber is the most commonly utilized due to its affordability. This type of fiber is particularly well-suited for applications requiring high tensile and compressive strength, as well as stiffness…

Carbon fiber materials are commonly employed in applications requiring high tensile and compressive strength, as well as stiffness. These materials have gained popularity in the transport and aerospace industries due to their low thermal expansion, electrical conductivity, and strength.

In contrast, aramid fiber materials are highly valued for their exceptional tensile strength and low compression and bending strength. Their weight-dependent stiffness makes them particularly useful for parts that are subjected to purely tensile loads. With their low thermal expansion and high tensile strength, aramid fibers are well-suited to meet a wide range of structural requirements in lightweight construction.

Types of reinforcement materials 

Glass fiber

The fundamental components of glass fiber reinforcement are filaments that typically range in diameter from 10 to 30 micrometers. These filaments are created by drawing molten glass through platinum nozzles. Multiple filaments are then combined to form a yarn, with varying weights depending on the number of filaments: 204 filament yarn weighs between 40 and 50 tex (40-50 grams per 1000 meters), 102 filament yarn weighs 20 tex (20 grams per 1000 meters), and 51 filament yarn weighs 10 tex (10 grams per 1000 meters).

While glass mats with a smooth texture are available, those with a higher texture are more commonly used as they are better able to absorb resin.

To create roving fiber, sixty (or thirty) untwisted yarns are combined and used for spray-up application or wrap roving. Rovings typically weigh 1200 or 2400 tex and serve as reinforcement material.

In order to produce a reinforcement mat, roving fibers are processed on a loom, much like textile fibers. A variety of fabrics are in demand, with linen and 2/2-twill being economically significant today.

Legs, which are made of loose layers without woven threads, consist of layers oriented in a single direction (0°, 90°, or even 45° and -45°) and are stitched together. Due to their straight uni- or bi-axial threads, multi-layered molded parts are especially rigid.

Cut glass fibers (cut glass) are obtained by cutting roving strands into lengths ranging from 3 to 13 millimeters. They are often used in conjunction with other fillers in other fiber resins and bonding pastes.

Mats

Matting material is created by cutting strands of wire, either 25 or 50mm in length, which are then formed into mats. These mats are used in a variety of processes, including pressing, filmmaking, injections, and vacuum injections, especially when the resin used has low flow resistance. Two different methods are used to bind the glass threads of the mat together, depending on the production method. In the manual process, the threads are held together with a slightly soluble styrene, while the pressing method employs a binder that is difficult or insoluble in styrene.

Powdered polyester resin is a common binder for mats, and it is classified as a powder binder. This type of binder results in a clear impregnation of the mat with transparent resin and offers good water resistance in most cases. Another method of bonding the threads of the mat together is through the use of a polyvinyl acetate/water emulsion, which is referred to as an emulsion binding. While these mats can offer advantages during processing, the emulsion binder can create a milky appearance in transparent laminates and generally results in reduced water resistance in laminates.

Mats are highly malleable and can be shaped to fit a variety of surfaces. Some mats have thermoplastic binders that can be preformed by heating. The deformability of mats makes them ideal for application on spherical curved surfaces without creating wrinkles.

Fiberglass fabric is created by weaving together glass threads, roving strands, or twisted yarns. The threads can be woven in a symmetrical pattern to achieve equal filament weight in both directions, or the weft direction can be lighter. Fabrics with material in both directions are classified as bi-directional, while those with only one direction are called unidirectional.

Complex two-layer fabrics consist of a glass mat and roving fabric or layers, held together by a binding thread. These typically weigh between 600-1200 g/m2. Three-layer complexes have an added fleece layer to improve interlaminar shear strength, and weigh around 50 g/m2.

Complexes reduce the cost of tailoring and draping in mold components. Pellicle complexes are a special type where a fleece layer is sandwiched between two cut mats or a mat and fabric, creating a material that is highly deformable but retains its shape when bent in a straight direction. They are attached twice and weigh between 800-1500 g/m2, and are often used in vacuum processes.

Equipment of the filament surface 

To process fiberglass for textile use, a textile finish is applied to filaments to prevent damage, while mats and rovings receive an adhesive finish. After weaving and priming, the fabric is rearranged, usually through heat treatment.

Various adhesives, such as aminosilanes, epoxy silanes, and modified Volan-A

Carbon fiber

The addition of an epoxy-based plastic finish during fiber production enables these materials to be compatible not only with epoxy resins, but also with certain types of vinyl and polyester resins during processing.

Aramid fiber

These materials can be surface finished with epoxy resin even without special equipment, and they can also be finished with vinyl ester and some polyester resins.