Abstract
Sandwich structures utilize the geometric stiffening effect by increasing the area moment of inertia. This reduces carbon fiber (CF) material within CF-reinforced plastic (CFRP) components, and thus, the CO2 footprint. A suitable material combination for lightweight design is the use of continuous fiber-reinforced face sheets with a light foam core. CFRP sandwich structures with foam core are manufactured by combining a prefabricated foam core with fiber-reinforced cover layers in a two-step press process. Besides the reduction of the used CFRP material, more efficient manufacturing processes are needed. The aim of this paper is to develop a novel polyurethane foam system to enable the direct sandwich composite molding (D‑SCM) process for the production of CFRP sandwich structures by utilizing the resulting foaming pressure during the reactive polyurethane (PUR) foam system expansion for the impregnation of the CF reinforced face sheets. The developed formulation enables D-SCM structures with 150–250 kg/m3 foam density and 44–47.5% fiber volume content, based on a preliminary evaluation.
Highlights
Efforts to reduce environmentally harmful emissions and the increasingly holistic approach towards the consideration of the entire component life cycle from manufacture to disposal increase the pressure on material and production processes developments
This paper focuses on the material characterization and development as a basis for the described direct sandwich composite molding (D-SCM) process approach
The fabric layup for the face sheets affects the necessary compaction pressure to achieve the highest possible fiber volume contents, and the C1 configuration should be chosen for the process
Summary
Efforts to reduce environmentally harmful emissions and the increasingly holistic approach towards the consideration of the entire component life cycle from manufacture to disposal (life cycle assessment) increase the pressure on material and production processes developments. The superior specific properties of carbon fiber-reinforced plastic (CFRP) structures and the weight and emission savings they offer are offset by significantly higher resource consumption during material extraction (greenhouse gas impact of 38.9 kg CO2-equivalent per kg CF [1]) and component manufacture. This burden at the beginning of the product life cycle must be reduced, especially when carbon fibers are used, in order to achieve an advantage over conventional materials when balancing the entire component life cycle. Besides CF reinforcements, glass and flax fiber reinforcements are within the focus of current research activities, e.g., for cladding wall panels [6,7,8]
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