Thick and thin-ply CFRP laminates were mechanically characterized with and without steel foil reinforcement.
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Local steel foil reinforcement around holes can overcome the notch sensitivity of thin-ply composites.
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The onset (0.5%) and 2% bearing strength of the thick-ply CFRP were more than doubled with the addition of steel foils.
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Onset bearing strength of the hybrid CFRP are also higher than the ultimate strength of the pure CFRP.
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Ply thicknesses may be tuned to generate stable damage propagation in the hybrid configuration.
Abstract
The effect of ply thickness on the notch sensitivity and bearing properties on carbon fibre reinforced polymer composites and their hybrid laminates with steel foils were studied. Laminates with ply thicknesses of 0.3 mm and 0.03 mm comprising of CFRP and hybrid laminates were manufactured and characterized using tension, open hole tension and double lap bearing tests. A 25% ply substitution was found to double the bearing load with extensive plastic deformation in the joint while maintaining high stress and maintaining constant cross-sectional thickness in the laminate. With a good agreement between the finite element predicted values and failure behaviour, the damage initiation and progression behaviour could be observed experimentally. We numerically captured (i) rapid failure of 0° plies in the thin ply CFRP hybrid and (ii) continuous delamination with significant plastic deformation for the thick ply CFRP hybrid. The numerical results significantly reduce future experimental work when designing hybrid laminates and could allow the laminate lay-up to be tailored for load cases. Both the experiments and numerical models underline the distinct size effects occurring with respect to the ply thicknesses when hybridising a very ductile metal with a brittle yet strong composite material.
