Continuous–Discontinuous Fiber-Reinforced Polymers

Composite materials have ushered in a new era in materials science and engineering, allowing the design of engineered materials with superior mass-specific mechanical properties. Current demand in the transportation and energy sectors to reduce carbon dioxide emissions has motivated designs with such materials, a trend expected to increase in the coming years.

Chopped glass and carbon fiber sheet molding compounds (GF-SMC and CF-SMC) offer excellent characteristics concerning complex part geometry, functional integration, material utilization, and productivity at reasonable costs. However, limited fiber length and insufficient process control over fiber orientation restrict mechanical strength and stiffness.

Hybrid composite materials offer a more interesting profile of properties than bulk materials, including properties that can be adjusted via the composite architecture. However, they also represent a major challenge, particularly regarding material characterization. Although the resulting material properties in common composites often result in “compromise properties” of the characteristic values of the individual components, hybrid composites are commonly characterized by the occurrence of additional synergy effects. This is especially true when physical and mechanical properties are combined, but may also apply to purely structural aspects.

Despite extensive research during recent decades, theoretical and computational modeling of fiber-reinforced polymer materials still poses many open issues and challenges. This is not surprising, since new material systems are steadily being developed, including hybrids containing phases with continuous and discontinuous fiber reinforcement.

Combining continuous and discontinuous fibers in structural composite components increases both the component’s lightweight potential and the engineer’s design freedom. The additional design freedom, however, comes at the price of greater variety in the design parameters, which are strongly interdependent and thus difficult to optimize simultaneously.

A demonstrator structure is used in IRTG to exemplify the established fabrication technology of CoDiCoFRP structures. The tasks of designing and optimizing the composite structure and then optimizing the process chain using conventional trial-and-error methods are quite time-consuming and expensive. Here, virtual process chain simulations can streamline the process.