Fig. 1 Terminology of CoFRP, DiCoFRP and CoDiCoFRP
For CoFRP, the orientation distribution and arrangement of continuous fibers are approximately homogeneous, whereas for DiCoFRP both the orientation distribution and the spatial arrangement of fibers show a significant degree of inhomogeneity and randomness. Furthermore, fiber congregations and optional filler particles may be present in DiCoFRP materials. This strong spatial inhomogeneity is induced by the manufacturing process.
Fiber Reinforced Thermoplastics and Thermosets
In the context of discontinuous fiber reinforced thermoplastics, the classification of the materials is usually introduced based on the average fiber length. The separation between short fiber and long fiber reinforced composites (LFT) manufactured in compression molding is usually in the range of approximately 4 mm.
For thermoset based discontinuous fiber reinforced materials, the description is oriented on the manufacturing process of the compound, like bulk molding compound (BMC) or sheet molding compound (SMC). In the case of SMC there is no precise generally accepted separation concerning the used fiber lengths.
In order to have a unified notation for all of the aforementioned composite types with respect to the fiber arrangement and the polymer system, thermoset (TS) or thermoplastic (TP), the aforementioned three classes are subdivided into CoFRTS/DiCoFRTS /CoDiCoFRTS and CoFRTP/DiCoFRTP/CoDiCoFRTP, respectively (Fig. 1).
Fig. 2 Abbreviations for different classes of composites with specification of the polymer system
Combining the Advantages of two types of reinforcements
The main advantage of DiCoFRP is their bulk material flow capability, which - compared to CoFRP - increases the design freedom for components significantly.
The benefit of CoFRP is the high load-bearing capacity, which is much higher compared to DiCoFRP.
From an engineering point of view, an optimal combination of design options on the one hand and high stiffness and strength on the other hand can be obtained by combining DiCoFRP with local continuous fiber reinforcements (CoDiCoFRP) (Fig. 2).
Fig. 3 Backseat made of DiCoFRP with steel frame (left) and single component of CoDiCoFRP (right)
In contrast to CoFRP like woven or non-crimp fabrics, for which established design strategies exist, which are successfully used in CoFRP engineering applications, the design strategies for CoDiCoFRP are to be developed in order to use CoDiCoFRP in structural applications.