Carbon epoxy temperature effects

Ray BC. Temperature effect during humid ageing on interfaces of glass and carbon fibers reinforced epoxy compxjsites. J Colloid Interface Sci 2006 298 111-117. 

Detassis M, Pegoretti A and Migliai esi C (1995) Effect of temperature and strain rate on iuterfacial shear stress transfer in carbon/epoxy model composites. Compos Sci Technol 53 39—46. 

The general effect of most fillers is to reduce the coefficient of thermal expansion of the cured epoxy resin in proportion to the degree of filler loading. Certain fillers, such as zirconium silicate and carbon fiber, have a negative coefficient of thermal expansion. These are very effective in lowering the expansion rate of the epoxy, especially at elevated temperatures. 

In order to study the effect of physical aging on the carbon-fiber reinforced epoxy, the freshly quenched materials were then sub-Tg annealed at 140 °C. After annealing for only 10 minutes at that temperature, the toughness of the composite was restored to a level comparable to that of the postcured material (see Fig. 7). It is likely that residual thermal stresses resulted from the quenching were annealed away during this 10 minutes thermal aging at 140 °C. 

Major results. Figure 14.7 shows that the resistivity of aluminum-filled PMMA changes abruptly. Smaller volumes of filler contribute a little to resistivity but, after certain threshold value of filler concentration, further additions have little contribution. A similar relationship was obtained for nickel powder the only difference is in the final value of resistivity, which was lower for nickel due to its higher conductivity. The same conclusions can be obtained from conductivity deteiminations of epoxy resins filled with copper and nickel. Figure 14.8 shows the effect of temperature on the electric conductivity of butyl rubber filled with different grades of carbon black. In both cases, conductivity decreases with temperature, but lamp black is substantially more sensitive to temperature changes. Even more pronounced changes with temperature were detected for the dielectric loss factor and dissipation factor for mineral filled epoxy." ... 

Dutta and Ryan (1979) examined the effects of fillers (carbon black and silane-surface-treated silica) on the cure of DGEBA/MPDA epoxy-amine systems. They found that the rate constants of the cure reaction are affected by the presence of the fillers in an unusual fashion (a function of temperature and concentration) with respect to concentrations up to 10%. This was postulated to be due to the reactive surface groups on the fillers. The reaction order, however, is not affected. 

Liou et al. [13] have measured the effect of absorbed moisture on the thermal expansion coefficients of carbon fibre epoxy laminates. Moisture lowers the transverse coefficient, but has little effect on Oi at room temperature. Failure in some epoxy laminates used to make multilayer PCBs has been traced to high z-axis thermal expansion stresses on marginal plated-through holes. Moisture is a factor, and complete drying can sometimes eliminate the problem [14]. 

Katouzian M, Bruller OS, Horoschenkoff A, On the effect of temperature on the creep-behaviour of neat and carbon-fiber-reinforced PEEK and epoxy-resin, J Composite Mater, 29(3), 372 387, 1995. 

Figure 20.26 Variation of longitudinal compressive strength of carbon fiber epoxy resin laminate with temperature showing transition from shear mode to buckling mode failure. Failure depends on the shear modulus of the matrix and shear strength of the fibers and a similar effect is observed with the uptake of water. Source Reprinted with permission from Ewins PD, Potter RT, Phil Trans R Soc London, A294, 507-517, 1980. Copyright 1980, The Royal Society of Chemistry.

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