The MN+1AXN phases: A new class of solids

On the compressive failure of fiber reinforced composites

https://dr.ntu.edu.sg/bitstream/10356/82404/2/Characterization%20of%20mechanical%20properties%20and%20fracture%20mode%20of%20additively%20manufactured%20carbon%20fiber%20and%20glass%20fiber%20reinforced%20thermoplastics.pdf

Characterization of mechanical properties and fracture mode of additively manufactured carbon fiber and glass fiber reinforced thermoplastics

Transmission electron microscopy (TEM) of aligned, macrograined samples of Ti3SiC2, deformed at room temperature, shows that the deformed microstructure is characterized by a high density of perfect basal-plane dislocations with a Burgers vector of 1/3〈112 0〉. The dislocations are overwhelmingly arranged either in arrays, wherein the dislocations exist on identical slip planes, or in dislocations walls, wherein the same dislocations form a low-angle grain boundary normal to the basal planes. The arrays propagate across entire grains and are responsible for deformation by shear. The walls form as a result of the formation of kink bands. A dislocation-based model, that builds on earlier ideas proposed for kink-band formation in hexagonal metallic single crystals, is presented, which explains most of the microstructural features. The basic elements of the model are shear deformation by dislocation arrays, cavitation, creation of dislocation walls and kink boundaries, buckling, and delamination. The delaminations are not random, but successively bisect the delaminating sections. The delaminations and associated damage are contained by the kink boundaries. This containment of damage is believed to play a major role in endowing Ti3SiC2 and, by extension, related ternary carbides and nitrides with their damage-tolerant properties.

Dislocations, kink bands, and room-temperature plasticity of Ti 3 SiC 2

Compressive failure of composites, part I: Testing and micromechanical theories

This paper describes the behaviour of a carbon-fibre reinforced epoxy composite when deformed in compression under high hydrostatic confining pressures. The composite consisted of 36% by volume of continuous fibres of Modmur Type II embedded in Epikote 828 epoxy resin. When deformed under pressures of less than 100 MPa the composite failed by longitudinal splitting, but splitting was suppressed at higher pressures (up to 500 MPa) and failure was by kinking. The failure strength of the composite increased rapidly with increasing confining pressure, though the elastic modulus remained constant. This suggests that the pressure effects were introduced by fracture processes. Microscopical examination of the kinked structures showed that the carbon fibres in the kink bands were broken into many fairly uniform short lengths. A model for kinking in the composite is suggested which involves the buckling and fracture of the carbon fibres.

C. W. Weaver

Papers

Deformation of a carbon-epoxy composite under hydrostatic pressure