Effect of Stress Ratio on Fatigue Behaviour of Non-Crimp Fabric Composites at Room and Elevated Temperatures
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Effect of Stress Ratio on Fatigue Behaviour of Non-Crimp Fabriccomposites at Room and Elevated Temperatures Trevor Sabiston 1,2 & Bin Li 1,2 & Jidong Kang 1 & Jie Liang 1 & David Wilkinson 2 & Carlos Engler-Pinto 3 Received: 18 March 2020 / Accepted: 27 May 2020/ # Crown 2020
Abstract
The fatigue behaviour of a biaxial carbon/epoxy Non-Crimp-Fabric (NCF) composite is evaluated at room temperature and 130o C for automotive applications. A new specimen geometry is developed allowing three stress ratios R = 0.1, R = −1 and R = 10 to be tested at 130o C without the use of anti-buckling fixtures for axial loadings. The three stress ratios show good agreement in fatigue life using an equivalent stress amplitude. The fracture surfaces from failed fatigue test specimens are compared to those of monotonic loading to evaluate the changes to failure modes under the different loading conditions. Tensile dominated loading such as uniaxial tension and fatigue testing with R = 0.1 result in delamination of the NCF material coupled with fibre failure along the loading direction as the primary failure modes. Compressive fatigue failures at 130 °C occur at an inclined angle through thickness due to a shearing process along with fibre kinking. The matrix material exhibits more ductile characteristics at 130o C altering the fracture surfaces at elevated temperature. Keywords Non-crimp fabric . Fatigue testing . Failure analysis . Fractography
* Jidong Kang [email protected]
1
Natural Resources Canada, CanmetMATERIALS, 183 Longwood Road South, Hamilton, Ontario L8P 0A5, Canada
2
Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton L8S 4L7, Canada
3
Research and Innovation Centre, Ford Motor Company, 2101 Village Road, Dearborn, MI 48124, USA
Applied Composite Materials
1 Introduction Non-Crimp Fabric (NCF) composites are of interest in the automotive industry as they can achieve similar strength and stiffness to unidirectional composites along with preferable draping characteristics of textile composites for manufacturing [1–5]. NCF composites have improved mechanical properties compared to woven textile composites due to the fibres unidirectional alignment [6]. NCF composites offer faster manufacturing compared to unidirectional composites using processes such as compression moulding due to the stitching yarns holding the unidirectional plies in place [7]. The stitching yarns also serve as reinforcement in the through thickness direction which increases delamination resistance [8, 9]. NCF composites are of interest for light-weighting of structural automotive components to increase the energy efficiency of vehicles through mass reduction. Composite structures have not performed well in the past under compressive loadings due to buckling and delamination of unidirectional plies. This presents a challenge for automotive design where structures are subjected to cyclic compressive loading. In internal combustion engine vehicle applications there is also a concern with elevat
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