Applied Composite Materials

Xia, Xiaoxin; McQueen, H.

doi: 10.1007/BF02481398pmid: N/A

Deformation and microstructural behaviours of a 20% (volume percent) particle reinforced 6061 Al matrix composite have been studied by torsion from 25 to 540°C with strain rates of 0.1, 1 and 5 s−1. The logarithmic stress versus reciprocal temperature relationship exhibits two slopes indicating different deformation mechanisms. The 20% Al2O3/6061 Al composite shows a greater hardening behaviour than those of the 10% Al2O3/6061 Al composite and of the monolithic alloy. Above 250°C, TEM investigations reveal much smaller subgrain size and higher volume of non-cellular substructures, as well as dynamic recrystallization nuclei in the 20% Al2O3/6061 Al composite in comparison to those of the 10% Al2O3/6061 Al composite and matrix alloy the same test condition. The torsion fracture surface was studied and compared to the three point bending failure specimens.

Tong, J.; Guild, F.; Ogin, S.; Smith, P.

doi: 10.1007/BF02481399pmid: N/A

Stable matrix crack growth behaviour under mechanical fatigue loading has been studied in a quasi-isotropic (0/90/-45/+45)s GFRP laminate. Detailed experimental observations were made on the accumulation of cracks and on the growth of individual cracks in +45° as well as 90° plies. A generalised plain strain finite element model of the damaged laminate has been constructed. This model has been used to relate the energy release rate of growing cracks to the crack growth rate via a Paris relation.

Dubey, S.; Soboyejo, W.; Srivatsan, T.

doi: 10.1007/BF02481400pmid: N/A

This paper discusses the tensile response and fracture toughness of in-situ titanium alloy metal matrices discontinuously-reinforced with whiskers of titanium boride which were success-fully produced by ingot metallurgy techniques. Additions of elemental boron resulted in a near uniform dispersion of the rod-like titanium boride (TiB) reinforcements in the alloy matrix. Such composites have engendered considerable scientific and technological interest due to their attractive combinations of improved mechanical properties and low manufacturing cost. The improved elastic moduli of the composites are explained using shear lag and rule-of-mixtures theories. The increased strengths of the in-situ composites are rationalized by considering the combined effects of deformation restrains imposed by the stiff whiskers and strengthening contributions arising from the substructure that evolves from the presence of additional dislocations.

Daymond, Mark; Withers, Philip

doi: 10.1007/BF02481401pmid: N/A

A novel stroboscopic neutron diffraction data collection system has been developed. In combination with scanning laser extensometry this has been used to investigate the thermal cycling behaviour of SiC short fibre reinforced Al matrix composites. Three-dimensional unit cell finite element models have been produced, incorporating matrix deformation both by creep and plasticity. Comparison of the experimental results with model predictions has allowed conclusions to be drawn about the deformation processes which dominate at different parts of the thermal cycle.