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Lecture

Fatigue damage behavior of continuous-discontinuous fiber reinforced sheet molding compounds

Tuesday (28.04.2020)
14:40 - 15:00 Room 1

Continuous fiber reinforced polymers feature high strength and high stiffness. However, they are limited in terms of design freedom and their production costs are high. In contrast, discontinuous fiber reinforced polymers show lower mechanical properties but provide increased design freedom at lower production costs. Continuous-discontinuous fiber reinforced polymers aim to combine the advantages of both composite materials and therefore have significant potential for different engineering applications, as for example in the automotive industry. Corresponding parts are mainly subjected to cyclic loads, however, prediction of their fatigue properties is proving difficult. Achieving this objective requires profound knowledge about the damage mechanisms. In this work, the fatigue behavior of continuous-discontinuous sheet molding compounds was investigated in a load-controlled tension-tension fatigue test under different loads. Carbon fibers function as continuous reinforcement whereas glass fibers are used for the discontinuous reinforcement. The matrix material is an unsaturated polyester polyurethane hybrid resin system without fillers. Damage evolution was analyzed visually. Digital image correlation was used for deformation analysis. Progressive damage of the continuous layers in form of interfiber fracture and fiber breakage begins with the first cycle at the edges of the specimen. Delamination and final failure of these layers preceded failure of the discontinuous phase. The constraining effect of the continuous layer at an early stage of fatigue has a positive effect on the damage behavior of the discontinuous phase. Compared to experimental data determined for the discontinuous composite, considerably higher fatigue strength is achieved.

Speaker:
Miriam Bartkowiak
Karlsruhe Institute of Technology (KIT)
Additional Authors:
  • Prof. Dr. Kay André Weidenmann
    University of Augsburg