Measuring deformation and mechanical properties of weld lines in short fibre reinforced thermoplastics using digital image correlation

• Published in: Polymer testing Vol. 36; pp. 44 - 53
• Main Authors: Kalus, Jakub, Jørgensen, Jens Kjær
• Format: Journal Article
• Language: English
• Published: Kindlington Elsevier Ltd 01-06-2014; Elsevier
• Subjects: Applied sciences; Composites; Correlation analysis; Digital; Digital image correlation; Exact sciences and technology; Forms of application and semi-finished materials; Injection moulding; Mechanical properties; Polymer industry, paints, wood; Short fibre reinforced plastics; Short fibres; Strength; Technology of polymers; Thermoplastic resins; Weld lines; Injection moulding; Weld lines; Short fibre reinforced plastics; Digital image correlation; Elastic modulus; Short fiber; Nylon; Fiber reinforced material; Mechanical properties; Digital image; Experimental study; Deformation measurement; Injection molding
• ISSN: 0142-9418; 1873-2348
• DOI: 10.1016/j.polymertesting.2014.03.017

Weld lines in injection moulded short fibre reinforced thermoplastics can significantly reduce the mechanical strength of a product. However, knowledge about the mechanical properties in the weld line region is limited. A reason for this is the difficulty in measuring strains at small scales. In this study, the feasibility and usefulness of high spatial resolution digital image correlation to measure strain profiles in the weld line region is demonstrated on a short fibre reinforced polyamide. The elastic modulus of weld lines in the reinforced material was determined to be equal to the matrix modulus, while the weld line strength was higher than the bulk matrix material. A suggested explanation for the strength increase is that fibres, although not crossing the weld line, reinforce it by preventing necking.