Abstract
The mechanics of damage and fracture process in unidirectional carbon fiber reinforced polymer (CFRP) composites subjected to shear loading (Mode II) were examined using the experimental method of the three-point end-notch flexure (3ENF) test. The CFRP composite consists of [0o]16 with an insert film in the middle plane for a starter defect. A 3ENF test sample with a span of 50 mm and interface delamination crack length of 12.5 mm was tested to yield the load vs. deformation response. A sudden load drop observed at maximum force value indicates the onset of delamination crack propagation. The results are used to extract the energy release rate, GIIC, of the laminates with an insert film starter defect. The effect of the starter defect on the magnitude of GIIC was examined using the CFRP composite sample with a Mode II delamination pre-crack. The higher magnitude of GIIC for the sample with insert film starter defect was attributed to the initial straight geometry of the notch/interface crack and the toughness of the resin at the notch front of the fabricated film insert. The fractured sample was examined using a micro-computerized tomography scanner to establish the shape of the internal delamination crack front. Results revealed that the interface delamination propagated in a non-uniform manner, leaving a curved-shaped crack profile.
Highlights
Laminated carbon fiber reinforced polymer (CFRP) composites exhibit customizable top-of-the-range properties, making them suitable for structural materials in various engineering applications, including in transportations, infrastructures, energy, marine, and sports and leisure
The delamination resistance of CFRP composites is commonly represented by interlaminar fracture toughness, which is often identified as critical strain energy release rate (GC )
This study examines the physical aspect of crack initiation and growth of a unidirectional CFRP composite experiencing delamination under Mode II by 3ENF test
Summary
Laminated carbon fiber reinforced polymer (CFRP) composites exhibit customizable top-of-the-range properties, making them suitable for structural materials in various engineering applications, including in transportations, infrastructures, energy, marine, and sports and leisure. CFRP composites have relatively low interlaminar strength, making them susceptible to delamination damage, that might happen during manufacture or in service [1]. The presence and growth of delamination in CFRP composites may significantly reduce their stiffness, compromising their structural integrity, and even leading to a catastrophic failure. Considering these, delamination resistance of CFRP composites must be measured reliably and be taken into account in the design and manufacture of CFRP composites [1]. The delamination resistance of CFRP composites is commonly represented by interlaminar fracture toughness, which is often identified as critical strain energy release rate (GC ).
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