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Development of a process to apply uniform pressure to bond CFRP patches to the inner surface of undercut-shaped sheet metal parts  

Lee, Hwan-Ju (Department of Automotive Engineering, Kookmin University)
Jeon, Yong-Jun (Shape Manufacturing R&D Department, Korea Institute of Industrial Technology)
Cho, Hoon (Shape Manufacturing R&D Department, Korea Institute of Industrial Technology)
Kim, Dong-Earn (Shape Manufacturing R&D Department, Korea Institute of Industrial Technology)
Publication Information
Design & Manufacturing / v.14, no.4, 2020 , pp. 65-70 More about this Journal
Abstract
Partial reinforcement of sheet metal parts with CFRP patch is a technology that can realize ultra-lightweight body parts while overcoming the high material cost of carbon fiber. Performing these patchworks with highly productive press equipment solves another issue of CFRP: high process costs. The A-pillar is the main body part and has an undercut shape for fastening with other parts such as roof panels and doors. Therefore, it is difficult to bond CFRP patches to the A-pillar with a general press forming tool. In this paper, a flexible system that applies uniform pressure to complex shapes using ceramic particles and silicone rubber is proposed. By benchmarking various A-pillars, a reference model with an undercut shape was designed, and the system was configured to realize a uniform pressure distribution in the model. The ceramic spherical particles failed to realize the uniform distribution of high pressure due to their high hardness and point contact characteristics, which caused damage to the CFRP patch. Compression equipment made of silicone rubber was able to achieve the required pressure level for curing the epoxy. Non-adhesion defects between the metal and the CFRP patch were confirmed in the area where the bending deformation occurred. This defect could be eliminated by optimizing the process conditions suitable for the newly developed flexible system.
Keywords
CFRP patchwork; Flexible mold; Undercut; Multi-material; Sheet metal forming; Bonding;
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