Reduced weld strength due to secondary cell formation in vibration weld region of microcellular glass fiber reinforced nylon-6 shells

Microcellular plastic parts reduce weight and increase dimensional stability, but a significant decrease in weld strength is observed when the weld region reaches the cell area. In this study, 30 wt.% glass fiber reinforced nylon-6 shells with weight reductions of 0%, 7%, and 10% were fabricated by...

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Bibliographic Details
Published in:Welding in the world 2019-06, Vol.63 (4), p.1115-1120
Main Authors: Guo, Tianhao, Edrisy, Afsaneh, Eichhorn, S. Holger, Vanderveen, Jim, Baylis, Bobbye, Colwell, Harold
Format: Article
Language:English
Subjects:
Automotive parts
Chemistry and Materials Science
Dimensional stability
Fiber reinforced polymers
Fracture surfaces
Free surfaces
Glass fiber reinforced plastics
Injection molding
Materials Science
Metallic Materials
Microscopy
Microstructural analysis
Nucleation
Optical microscopy
Research Paper
Scanning electron microscopy
Shell stability
Solid Mechanics
Surface layers
Theoretical and Applied Mechanics
Vibration welding
Weight reduction
Weld strength
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Summary:Microcellular plastic parts reduce weight and increase dimensional stability, but a significant decrease in weld strength is observed when the weld region reaches the cell area. In this study, 30 wt.% glass fiber reinforced nylon-6 shells with weight reductions of 0%, 7%, and 10% were fabricated by microcellular injection molding with nitrogen gas followed by vibration welding. Although the weld depth of the vibration weld was much less than the thickness of the cell-free surface layer, microstructural analysis of fracture surfaces by scanning electron microscopy and optical microscopy confirmed the presence of cells at the weld region that lowered burst pressures by 17% and 22% for shells with weight reductions of 7% and 10%, respectively, when compared with the burst pressure of 1.16 MPa for solid shells. The irregular sizes and elongated shapes of these cells suggest that they were generated in the molten polymer by secondary nucleation of residual nitrogen gas during the vibration welding process. This assumption is corroborated by the fact that no cells are formed in the weld area of solid shells with 0% weight reduction and is consistent with recently reported similar findings for glass fiber reinforced polypropylene.
ISSN:0043-2288
1878-6669
DOI:10.1007/s40194-019-00729-w