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Investigation of Mechanical Properties of Thermoplastics with Implementations of LS-DYNA Material Models.
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
2012 (English)Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The increased use of thermoplastics in load carrying components, especially in the automotive industry, drives the needs for a better understanding of its complex mechanical properties. In this thesis work for a master degree in solid mechanics, the mechanical properties of a PA 6/66 resin with and without reinforcement of glass fibers experimentally been investigated. Topics of interest have been the dependency of fiber orientation, residual strains at unloading and compression relative tension properties. The experimental investigation was followed by simulations implementing existing and available constitutive models in the commercial finite element code LS-DYNA.

The experimental findings showed that the orientation of the fibers significantly affects the mechanical properties. The ultimate tensile strength differed approximately

50% between along and cross flow direction and the cross-flow properties are closer to the ones of the unfilled resin, i.e. the matrix material. An elastic-plastic model with Hill’s yield criterion was used to capture the anisotropy in a simulation of the tensile test. Residual strains were measured during strain recovery from different load levels and the experimental findings were implemented in an elastic-plastic damage model to predict the permanent strains after unloading. Compression tests showed that a stiffer response is obtained for strains above 3% in comparison to tension. The increased stiffness in compression is although too small to significantly influence a simulation of a 3 point bend test using a material model dependent of the hydrostatic stress.

Place, publisher, year, edition, pages
2012. , 48 p.
Keyword [en]
Glass-fiber reinforced thermoplastics, polyamide, Hill’s plasticity criterion, strain recovery, cyclic loading, cyclic softening, compression strength, 3 point bend test, LS-DYNA
National Category
Applied Mechanics
URN: urn:nbn:se:kth:diva-103790OAI: diva2:561650
Subject / course
Solid Mechanics
Educational program
Master of Science - Engineering Mechanics
Available from: 2014-04-09 Created: 2012-10-19 Last updated: 2014-04-09Bibliographically approved

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