• Design & Manufacturing
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• 제14권4호
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• pp.65-70
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• 2020

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.

• 대한기계학회논문집A
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• 제39권1호
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• pp.89-94
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• 2015

본 연구의 목적은 열처리 전 후의 보론강 레이저 용접성을 비교하는 것이다. 일반적으로 보론강이 핫스탬핑 공정에 사용되고 있으며, 핫스탬핑 공정은 강판을 오스테나이트 온도까지 가열한 후 성형과 동시에 냉각하는 방법이다. 열처리후 보론강은 1500 MPa 이상의 고강도를 가진다. 따라서 본 연구에서는 보론강 및 핫스탬핑강의 레이저 용접성을 조사한 후 비교하였다. CW 디스크 레이저를 이용하여 레이저 출력 및 용접속도를 변화시켜가며 맞대기 및 겹치기 용접을 실시하였다. 맞대기 용접 결과, 핫스탬핑강에서 완전 용입을 얻을 수 있는 임계냉각속도가 보론강보다 낮았으며, 겹치기 용접결과 완전 관통이 일어난 용접 조건에서는 접합부 폭은 용접속도와 관계없이 거의 유사하였다.