Matrix-dominant fracture

For smaller values of Vj, the behavior of the composite material might not follow Equation (3.84) because there might not be enough fibers to control the matrix elongation. That is, the matrix dominates the composite material and carries the fibers along for the ride. Thus, the fibers would be subjected to high strains with only small loads and would fracture. If all fibers break at the same strain (an occurrence that is quite unlikely from a statistical standpoint), then the composite material will fracture unless the matrix (which occupies only of the representative volume element) can take the entire load imposed on the composite material, that is. 

Improved mechanical properties. The addition of small size and low loading of nanoparticles will enhance the matrix-dominated properties such as stiffness, fracture toughness and interlaminar shear strength of conventional fiber-reinforced composites. 

If a composite with unidirectional fibres is loaded in tension or compression perpendicular to the fibre direction or in axial shear in fibre direction, it can fail without failure of the fibres by fracture, buckling, or kinking. These cases are therefore called matrix-dominated failure. 

Crossman FW, Warren WJ (1985) The infiuence of environment on matrix dominated composite fracture. Final report N60921-81-C-0157, Dec 1985 Crossman FW, Mauri RE, Warren WJ (1978) Moisture altered viscoelastic response of graphite/ epoxy composite. In Vinson JR (ed) Advanced Composite Materials - Environmental Effects, ASTM STP 658. American Society for Testing and Materials, Philadelpia, PA, pp 205-220 Ferry JD (1980) Viscoelastic Properties of Polymers. Wiley, New York Flaggs DL, Crossman FW (1981) Analysis of the Viscoelastic Response of Composite Laminates During Hygrothermal Exposure. Journal of Composite Materials 15(l) 21-40 Harper BD (1983) On the Effects of Post Cure Cool Down and Environmental Conditioning on Residual Stresses in Composite Laminates. Texas A M University Report MM-4665-83-11, Aug 1983... 

The ratio of the mode I interlaminar fracture toughness in 77K-LNj to that in RT-air was 1.8 for ALF/epoxy laminates. This ratio was decreased to 1.2 to 1.3 for CF/epoxy laminates. Thus, the increase of the matrix toughness was directly translated into the increase of the interlaminar fracture toughness for ALF/epoxy laminates. The effect was smaller for CF/epoxy laminates. Fractographic observation indicated foe contribution of resin is larger for ALF/epoxy laminates. Dominant interfacial fracture concealed the effect of resin for CF/epoxy laminates. 

Fracture process in multidirectional composite laminates subjected to in-plane static or fatigue tensile loading involves sequential accumulation of damage in the form of matrix cracks that appear parallel to the fibres in the off-axis plies, edge delamination and local delamination long before catastrophic failure. These resin dominated failure modes significantly reduce the laminate stiffness and are detrimental to its strength. 

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