Abstract
In this paper, the mechanical properties of fiber-reinforced epoxy laminates are experimentally tested. The relaxation behavior of carbon and glass fiber composite laminates is investigated at room temperature. In addition, the impact strength under drop-weight loading is measured. The hand lay-up technique is used to fabricate composite laminates with woven 8-ply carbon and glass fiber reinforced epoxy. Tensile tests, cyclic relaxation tests and drop weight impacts are carried out on the carbon and glass fiber-reinforced epoxy laminates. The surface release energy GIC and the related fracture toughness KIC are important characteristic properties and are therefore measured experimentally using a standard test on centre-cracked specimens. The results show that carbon fiber-reinforced epoxy laminates with high tensile strength give high cyclic relaxation performance, better than the specimens with glass fiber composite laminates. This is due to the higher strength and stiffness of carbon fiber-reinforced epoxy with 600 MPa compared to glass fiber-reinforced epoxy with 200 MPa. While glass fibers show better impact behavior than carbon fibers at impact energies between 1.9 and 2.7 J, this is due to the large amount of epoxy resin in the case of glass fiber composite laminates, while the impact behavior is different at impact energies between 2.7 and 3.4 J. The fracture toughness KIC is measured to be 192 and 31 MPa √m and the surface energy GIC is measured to be 540.6 and 31.1 kJ/m2 for carbon and glass fiber-reinforced epoxy laminates, respectively.
Highlights
Fiber-reinforced plastics (FRP) are used in many infrastructure and aerospace applications. These composites are usually used as laminates, which have higher specific strength and are lighter than standard metals
The mechanical properties of glass fiber-reinforced polymer (GFRP) structures were studied in [1,2,3,4] to understand the size effect produced by the hole under static loading
Fouad et al [9] measured the fracture toughness of epoxy resin reinforced with carbon fibers, Kevlar and glass fibers for biomedical applications
Summary
Fiber-reinforced plastics (FRP) are used in many infrastructure and aerospace applications. A work by Abdellah et al [7] studied the impact and relaxation loading of glass fiber-reinforced composite laminates. Saeed et al [21] studied stress relaxation at the interfaces of glass fiber-reinforced high density polyethylene (HDPE) These results were compared with Cox’s analytical model of shear retardation. The present work has two objectives: (1) to study the effect of stress increases (central open holes) on stress relaxation and (2) to understand delamination damage during a drop-weight impact test. These properties require a complete description of the fracture toughness and tensile properties of glass- and carbon fiber-reinforced polymers (GFRP and CFRP).
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