Characteristics and formation mechanism of porosities in CFRP during laser joining of CFRP and steel |
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| Affiliation: | 1. Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China;2. China Science Lab, General Motors (China) Investment Company Limited, Shanghai 201206, China;3. Key Laboratory for Advanced Materials Professing Technology, Ministry of Education, Tsinghua University, Beijing 100084, China;1. Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China;2. Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Tsinghua University, Beijing 100084, China;3. Shanghai Aerospace Equipments Manufacturer, Shanghai 200245, China;1. Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang, China;2. Shenzhen Institute, Peking University, Shenzhen, China;1. Joining and Welding Research Institute, Osaka University, Osaka 567-0047, Japan;2. DENGENSHA TOA CO., LTD., Kanagawa 214-8588, Japan;3. The Institute of Scientific and Industrial Research, Osaka University, Osaka 567-0047, Japan |
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| Abstract: | An experimental investigation on the mechanism of porosity formation during the laser joining of carbon fiber reinforced polymer (CFRP) and steel is presented. The porosity morphology and distribution were characterized by optical and scanning electron microscopy, and the thermal pyrolysis behaviors were investigated by thermal analysis and designed back-side cooling experiments. The results show that there are two types of porosities in CFRP. Porosity I only appears when the heat input is more than 77.8 J/mm. It has a smooth inner wall and distributes near the bonding interface between CFRP and steel at the central area of melted zone, which is caused by gaseous products such as CO2, NH3, H2O, and hydrocarbons produced by the pyrolysis of CFRP. Porosity II can be seen under all joining conditions. It has a rough inner wall and distributes far away from the bonding interface, concentrating at the final solidification locations. Porosity II is caused by the shrinkage of melted CFRP during solidification stage. |
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| Keywords: | A Polymer–matrix composites (PMCs) B Thermal properties B Porosity E Joints/joining |
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