Matrix toughness

Bradley, W.L. (1989b). Relationship of matrix toughness to interlaminar fraeturc toughness. In Application of Fracture Mechanics to Composite Materials (K. Fricdrieh ed.), Elsevier Seienec Pub., New York, Ch, 5, pp, 159-187. 

Russell, A.J. and Street, K.N. (1987). The effect of matrix toughness on delamination static and fatigue fracture under mode I and II shear loading of graphite fiber composites. In Toughened Composites. ASTM STP 937 (N.J. Johnston ed.). ASTM, Philadelphia, PA, pp. 257-294. 

Mechanical loading —> cavitation in rubber particles —> promotion of shear bands in matrix —> toughness improvement... 

Micromechanical modeling and available experimental evidence indicates that the composite toughness, KIc (composite), can be described as the sum of the matrix toughness, KIc (matrix), and a contribution due to whisker toughening, AKIc (whisker reinforcement).1,23 In other words,... 

Fig. 10.9 Curve showing the time needed for the stress intensity factor to attain Kc, the matrix toughness, as a function of the initial crack length, a. The curve has a C-curve appearance. The stable portion of the curve has a positive slope, and the unstable portion has a negative slope.

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. 

Figure 6. Effective toughening (Kf, normalized hy matrix toughness, K r) resulting from crack trapping as a function of the local crack advance, normalized hy particle diameter (dp). R/L = 0.125. Numerical results, shown by the curve, are from Bower and Ortiz (5, 29).

We observe that the composite toughness W = W /V can be increased, relative to the matrix toughness, by the addition of fillers when they are treated with SIC and TTS In the case of untreated beads, on the other hand, composite toughness always decreases with increasing 0 and is lower than matrix toughness. 

This change may be due to chemical decomposition or evaporation of residual styrene monomer or a combination of factors. The resin degrades at the upper end of the temperature range, but an increase in matrix toughness was observed over the range 10-40°C for a similar polyester [38] (Fig. 4.4). The increase was accompanied by a brittle-to-ductile transition, with changes in the fracture surface characteristics. 

OOaLee Lee, J., Yee, A. F. Role of inherent matrix toughness on fracture of glass bead filled epoxies. Polymer 41 (2000) 8375-8385. 

Methods used to increase matrix toughness have included modifying existing epoxy formulations by adding a second phase (such as rubber or a thermoplastic resin) that can absorb energy [3-7], using thermoplastic resins [8-11], and depositing a ductile material on the fiber surface [12-14]. 

Figure 4. Debond length vs. debond toughness/matrix toughness ratio a) for several values of the composite parameter k and the particle volume fraction / 0.15, b) for several values of the particle...

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