Carbon epoxy fatigue

Acoustic Emission to Model the Fatigue Behaviour of Quasi-Isotropic Carbon-Epoxy Laminate Composites. 

Lafarie-Frenot, M.C. and Henaff-Gardin, C., Formation and Growth of 90° Ply Fatigue Cracks in Carbon/Epoxy Laminates , Composites Science and Technology Vol. 40, p. 307-324, 1991... 

In particular, the techniques based on the termination of certain plies within the laminate has also shown promise. Static tensile tests of [30°/-30°/30°/90°]s carbon-epoxy laminates containing terminals of [90°] layers at the mid-plane show that premature delamination is completely suppressed with a remarkable 20% improvement in tensile strength, compared to those without a ply terminal. Cyclic fatigue on the same laminates confirms similar results in that the laminate without a ply terminal has delamination equivalent to about 40% of the laminate width after 2x10 cycles, whereas the laminates with a ply terminal exhibit no evidence of delamination even after 9x10 cycles. All these observations are in agreement with the substantially lower interlaminar normal and shear stresses for the latter laminates, as calculated from finite element analysis. A combination of the adhesive interleaf and the tapered layer end has also been explored by Llanos and Vizzini, (1992). 

Kawai M, Suda H. Effects of non-negative mean stress on the off-axis fatigue behavior of unidirectional carbon/epoxy composites at room temperamre. J Compos Mater 2004 38(10) 833-54. 

Kawai M, Taniguchi T. Off-axis fatigue behavior of plain weave carbon/epoxy fabric laminates at room and high temperatures and its mechanical modelling. Composites Part A 2006 37 243-56. 

Isa MD, Feih S, Mouritz AP. Compression fatigue properties of z-pinned quasi isotropic carbon epoxy laminate with barely visible impact damage. Compos Struct 2011 93 2269-76. 

The use of carbon fibres rather than glass improves water resistance considerably, although it does not guarantee immunity from water damage, because both the resin matrix and the interfacial bond can still be affected. The fatigue life of carbon/epoxy cross-ply laminates is actually shorter when the fatigue process is carried out on dry specimens than on those previously... 

Immersion in water does not always have adverse effects. Sometimes the properties improve, or some properties may improve and others deteriorate. Kosuri and Weitsman [79] and Smith and Weitsman [80] conducted fatigue tests (5Hz at 74-89% ultimate tensile strength) on cross-plied AS4/ 3501-6 prepreg carbon/epoxy laminates in three conditions ... 

P Chiou and W L Bradley, Effects of seawater absorption on fatigue crack development in carbon/epoxy EDT specimens . Composites 1995 26(12) 869-876. 

E-glass 3DNCOW composites and plain weave laminates were studied under inplane tensile fatigue loading in Carvelli et al. (2010). Carbon/epoxy 3DNCOW composites were studied under in-plane tensile fatigue loading by Karahan et al. (2011). 

Karahan, M., Lomov, S.V., Bogdanovich, A.E., Verpoest, I., 2011. Fatigue tensDe behavior of carbon/epoxy composite reinforced with non-crimp 3D orthogonal woven fabric. Compos. Sci. Technol. 71, 1961-1972. 

Figure 10.24 Effect of pre-conditioning on coupons undergoing tensile fatigue (a) carbon/epoxy (b) glass/epoxy (c) aramid/epoxy 65% rel. humidity for three months at 20°C (Jones et al.).

It is not clear from these data whether a fatigue limit does exist. There are, however, significant differences in the torque/shear strain curves when tested statically. Whereas the aramid/epoxy has a linear stress/strain curve, those of carbon/epoxy and glass/epoxy are distinctly non-linear. 

Figure 10.26 Compressive fatigue data for 0° and 45° specimens of carbon/epoxy with different gauge lengths (Lifschitz/ASTM).

The flexural fatigue data for both resin composites show that carbon/ PEEK has a lower degradation rate than that of carbon/epoxy for UD. The data for three alignments are contrasted in Table 10.5. 

Figure 10.27 Flexural fatigue data for carbon/PEEK and carbon/epoxy both for 0° laminates (Buggy and Dillon).

Ren Y, Fu YQ, Liao K, Li F, Cheng HM (2004). Fatigue failure mechanisms of single-walled carbon nanotube ropes embedded in epoxy. Appl. Phys. Lett. 84 2811-2813. 

Mai Y.W. (1988). Controlled inlerfacial bonding on the residual strength of fatigue-damaged carbon fiber-epoxy composites. J. Mater. Sci. Lett. 7, 581-582. 

Potanova, M.A., Poc, C.C., Whitecomb, J.D. (1992). Open hole and post-impact compressive fatigue of stitched and unstitched carbon fiber-epoxy matrix composites. In Composite Materials Testing and Design (lOlh Volume), ASTM STP-1120 (G.C. Grimes ed.), ASTM, Philadelphia, PA, pp. 37-53. 

Figure 29. Comparison of the fatigue behavior of 3D carbon-matrix (CFRC) and epoxy-matrix (CFRP) composites (53).

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