Integration of steel fibers (SF) in carbon fiber (CF) reinforced polymer composites (CFRPC) allows improvement of electrical conductivity while maintaining excellent mechanical properties, since SF also contribute to the load-carrying capacity. Due to their high ductility, also energy absorption and structural integrity can be improved. Within this study, a preforming process for hybrid carbon/SF preforms based on dry fiber placement (DFP) is developed and validated. The investigations cover the production of bindered SF rovings, the production of hybrid preforms via DFP of spread and nonspread SF rovings on CF noncrimp fabrics (CF-NCF) as well as the production of hybrid laminates via vacuum-assisted resin infusion (VARI). The laminate quality was evaluated by microscopic images and mechanical tensile testing. A higher SF volume content within the SF areas and more homogeneous SF layers in the preform (fewer matrix-rich zones) were achieved by processing nonspread SF rovings. The more homogeneous SF layers within the samples with nonspread SF rovings compared to spread SF rovings led to higher stiffness and strength of the specimens for tension loadings and therefore to best results.

Compaction behavior of textiles has a major influence on the outcome of various manufacturing processes for fiber reinforced polymer composites. Nevertheless, no standard exists up to date which specifies test methods or test rigs. A recent international benchmark revealed high variation associated with the result data. This work is a very first step toward a reference specimen, allowing for an isolated view on variations attributed to the test rig mechanics. A specimen design is proposed, intended to show compaction characteristics similar to technical textiles in terms of transverse compaction pressure and corresponding displacement. The reference specimen was tested in a round-robin study comprising test rigs at four different European research institutions. While reproducibility of the compaction behavior on each of the test rigs was high, clear variations between the results gained with different test rigs were observed.

No abstract

No abstract