Measuring constitutive shear behavior of orthotropic composites and evaluation of the modified Iosipescu test

• Published in: Composite structures Vol. 76; no. 1; pp. 106 - 115
• Main Authors: Melin, L. Niklas, Neumeister, Jonas M.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier Ltd 01.10.2006; Elsevier Science
• Subjects: Anisotropy; Applied sciences; Composites; Exact sciences and technology; Fixtures comparison and evaluation; Forms of application and semi-finished materials; Fracture mechanics (crack, fatigue, damage...); Fundamental areas of phenomenology (including applications); Inelasticity (thermoplasticity, viscoplasticity...); Modified Iosipescu test; Optical 3D monitoring of strains and desired/undesired displacements; Physics; Polymer industry, paints, wood; Shear properties; Solid mechanics; Strain field uniformity; Structural and continuum mechanics; TECHNOLOGY; Technology of polymers; TEKNIKVETENSKAP; Strain field uniformity; Optical 3D monitoring of strains and desired/undesired displacements; Shear properties; Modified Iosipescu test; Fixtures comparison and evaluation; Anisotropy; Constitutive equation; Fiber reinforced material; Displacement(deformation); Modeling; Work holder; Composite material; Deformation measurement; Inelasticity; Localization; Damaging; Shear test; High performance; Stress analysis; Notched test piece; Unidirectional fiber material; Notch; Anisotropic material; Clamping; Orthotropic material
• ISSN: 0263-8223; 1879-1085; 1879-1085
• DOI: 10.1016/j.compstruct.2006.06.016

The modified Iosipescu test uses a variable notch opening angle θ, depending on the material anisotropy and orientation, to accomplish even stress- and strain-fields in the test region. Constitutive shear properties can thus be measured more accurately, more completely, and with fewer sources of error. Here more materials and properties were studied, and a 3D optical strain- and displacement-monitoring system was used to evaluate and improve both the modified test and the novel fixture used here. It performed substantially better than the commonly used Wyoming fixture in terms of producing constant through specimen thickness conditions and preventing undesired specimen twisting. Additionally, loading–unloading behavior of two high-performance, essentially unidirectional, fiber composites was investigated to assess stiffness reduction, damage, localization, and irreversible strains. In the present of such, well controlled testing conditions are even more important.