Tensile properties of CFRP manufactured by resin transfer molding considering stacking sequences at various strain rates

Abstract

This paper is concerned with the improvement of a tensile test method and the material properties of carbon fiber reinforced polymer manufactured by resin transfer molding considering stacking sequences at various strain rates for auto-body. Auto-body structure experiences the strain rates up to several hundreds per second during car crash. In order to apply the carbon fiber reinforced polymer panel into auto-body structures, it is critical to acquire the material properties of carbon fiber reinforced polymer at various strain rates considering stacking sequences. The tensile test method is improved for acceptable test results. Test specimens are modified for high-speed tensile tests of carbon fiber reinforced polymer in order to achieve designated strain rates and eliminate the effect from unfavorable conditions of inhomogeneity of deformation. Various types of grip tab materials are employed for acceptable failure modes. Tensile tests have been carried out with non-crimp fabric made by 50K high strength carbon fiber (NCF) and woven fabric made by a 2/2 twill pattern of 3K high strength carbon fiber (TWILL) with different stacking sequences of 0° and 90° unidirectional cases as well as [0°/90°] and [45°/−45°] symmetric cases. Digital image correlation method and force equilibrium grid method are adopted for strain and stress measurement of a carbon fiber reinforced polymer specimen during a tensile test. The material properties acquired indicate that the carbon fiber has little rate dependency, while the epoxy matrix has remarkable rate hardening at strain rates from 0.001 s−1 to 100 s−1.

Specimen designs for accurate tensile testing of unidirectional composite laminates

“…Tapering the end tabs at 7° along the specimen length direction instead of a straight cut is suggested to have a gradual reduction of cross-section and consequently decrease stress concentrations. However, even these recommendations often do not lead to failure inside the gauge section and away from end tabs [4][5][6].…”

Static and dynamic mechanical properties of carbon fiber reinforced polymer with different stacking sequences

“…[11][12][13][14][15][16] Unlike isotropic metals such as steel, the mechanical properties of fiber reinforced composites are also affected by fiber type, matrix type, molding process, fiber volume fraction, ply direction, and stacking sequence. For compressive properties, Yoo et al 17 tested carbon fiber/epoxy laminates prepared by resin transfer molding (RTM), and the strain rate was ranged from 0.001 s À1 to 100 s À1 . The results show that the stress-strain curves in unidirectional 0°, 90°, and [0°/90°] layup are linear elastic, whereas the [45°/À45°] specimens behave as non-linear.…”