Compression fracture of unidirectional carbon fibre-reinforced plastics

Abstract

The effect of volume fraction and tensile strength of fibres, temperature and stress concentrators on the compression strength and fracture mode of unidirectional CFRP was studied. The cause of kinking is different for composites reinforced by low-(< 3 G Pa) and high-strength fibres. If fibre strength is high, the kink is initiated by composite splitting followed by fibre bend fracture in the tip of the split. In the case of low-strength fibres, kinking is initiated by compressive fracture of the fibres. The effect of stress concentrators on the CFRP compressive strength is described by linear fracture mechanics. In the presence of defects, fracture is a result of the emergence of splits near a hole. As the critical stress of splitting growth initiation reduces in proportion to the square root of the defect size, the Griffith criterion describes the composite compressive fracture. At elevated temperature, failure is caused by fibre buckling. The fracture band in this case is oriented perpendicular to the fibre direction. Carbon fibre compressive strength may be measured by the loop method. Bending a strand of carbon fibres glued to the elastic beam gives a fibre-controlled upper limit of the composite compressive strength.

Effect of temperature on kinking failure mode of non-slender glass fiber-reinforced polymer specimens

“…A shift from splitting to kinking failure at elevated temperatures was observed in [16,17] and was attributed to the softening of the matrix and http://dx.doi.org/10.1016/j.compstruct.2015.07.054 0263-8223/Ó 2015 Elsevier Ltd. All rights reserved.…”

A rigid-rod dihydroxy poly(p-phenylene benzobisoxazole) fiber with improved compressive strength

“…A filament loop was placed in light oil between two glass slides (Furuyama et al, 1993). The loop was successively deformed by pulling on both ends of the filament, with its longitudinal and transverse dimensions being measured by optical microscope (Bazhenov & Kozey, 1991). Theoretically (Sinclair, 1950), the fiber compressive strength (r f ) can be calculated from…”

“…The fiber elastic modulus under compression was assumed to be equal to its tensile modulus (Bazhenov & Kozey, 1991). The test results were averaged after examining twenty samples.…”

“…Nonlinear behaviour is a typical phenomenon not only for high-modulus fibers, but also for new super-high strength T-800 fibers, as which was showed by Jones and Johnson (1971). Subsequently, Bazhenov and Kozey (1991) using loop test method studied the compressive strength of carbon fibers.…”

Relation between interfacial shear strength and compressive strength of carbon fiber/epoxy resin composite strands

“…This equation has been derived by assuming that a misaligned fiber bundle, which will be observed as a kink band after fracture of the composite, pre-exists in the unloaded composite and has two parallel boundaries making an angle β with the transverse direction of the composite. For carbon fiber reinforced composites, a fracture leaving kink bands dominates as compared with the elastic microbuckling induced fracture [1,6]. Longitudinal splitting and delamination of a part of the composite can also trigger the fracture of the composite [6,7].…”