Anisotropic Elastic-Viscoplastic Properties at Finite Strains of Injection-Moulded Low-Density Polyethylene

• Published in: Experimental mechanics Vol. 58; no. 1; pp. 75 - 86
• Main Authors: Kroon, M., Andreasson, E., Persson Jutemar, E., Petersson, V., Persson, L., Dorn, M., Olsson, P.A.T.
• Format: Journal Article
• Language: English
• Published: New York Springer US 2018; Springer Nature B.V
• Subjects: Anisotropic; Anisotropic elastic; Anisotropy; Biomedical Engineering and Bioengineering; Characterization and Evaluation of Materials; Compliance matrixes; Constitutive behaviour; Construction materials; Control; Cyclic loads; Dynamical Systems; Elastic anisotropy; Elastic properties; Elastic-viscoplasticity; Elasticity; Engineering; Image analysis; Injection molding; Injection-moulding; Lasers; LDPE; Low density polyethylenes; Manufacturing process; Maskinteknik; Mechanical Engineering; Mechanical properties; Modulus of elasticity; Molding; Molding (process); Monotonic and cyclic loading; Optical Devices; Optics; Photonics; Plasticity; Plates (structural components); Polyethylene; Polyethylenes; Polymers; Solid Mechanics; Strain; Tensile; Tensile testing; Tensile tests; Thin walled structures; True strain; True stress; Vibration; Viscoplasticity; Polyethylene; Tensile; Injection-moulding; Constitutive behaviour; Viscoplasticity; Anisotropic; Elasticity; LDPE
• ISSN: 0014-4851; 1741-2765; 1741-2765
• DOI: 10.1007/s11340-017-0322-y

Injection-moulding is one of the most common manufacturing processes used for polymers. In many applications, the mechanical properties of the product is of great importance. Injection-moulding of thin-walled polymer products tends to leave the polymer structure in a state where the mechanical properties are anisotropic, due to alignment of polymer chains along the melt flow direction. The anisotropic elastic-viscoplastic properties of low-density polyethylene, that has undergone an injection-moulding process, are therefore examined in the present work. Test specimens were punched out from injection-moulded plates and tested in uniaxial tension. Three in-plane material directions were investigated. Because of the small thickness of the plates, only the in-plane properties could be determined. Tensile tests with both monotonic and cyclic loading were performed, and the local strains on the surface of the test specimens were measured using image analysis. True stress vs. true strain diagrams were constructed, and the material response was evaluated using an elastic-viscoplasticity law. The components of the anisotropic compliance matrix were determined together with the direction-specific plastic hardening parameters.