Fiber-reinforced composites transverse loading

Liu, Y. J., Xu, N., and Luo, J. R, Modeling of inter phases in fiber-reinforced composites under transverse loading using the boundary element method. Journal of Applied Mechanics, 67(1), 41 9 (2000). 

S. Jannson and F. A. Leckie, Mechanical Behavior of a Continuous Fiber-Reinforced Aluminum Matrix Composite Subjected to Transverse and Thermal Loading, Journal of the Mechanics and. Physics of Solids, 40, 593-612 (1992). 

The efficiency of reinforcement is related to the fiber direction in the composite and to the direction of the applied stress. The maximum strength and modulus are realized in a composite along the direction of the fiber. However, if the load is applied at 90° to the filament direction, tensile failure occurs at very low stresses, and this transverse strength is not much different than the matrix strength. To counteract this situation, one uses cross-pKed laminates having alternate layers of unidirectional libers rotated at 90°, as shown in Figure 3.47c. (A more isotropic composite results if 45° plies are also inserted.) The stress-strain behavior for several types of fiber reinforcement is compared in Figure 3.48. 

Weight-gain data were collected on uni-directionally reinforced AS4/3502 graphic/ epoxy composite coupons loaded transversely to the fiber direction as well as on neat 3502 samples. All specimens were exposed to RH = 98% and T = 40°C, with different samples loaded in tension at 0, 15, 30, and 45% of the dry epoxy failure stress of 52 MPa. 

One of the most important properties which control the damage tolerance under impact loading and the CAI is the failure strain of the matrix resin (see Fig. 8.8). The matrix failure strain influences the critical transverse strain level at which transverse cracks initiate in shear mode under impact loading, and the resistance to further delamination in predominantly opening mode under subsequent compressive loading (Hirschbuehler, 1987 Evans and Masters, 1987 Masters, 1987a, b Recker et al., 1990). The CAI of near quasi-isotropic composite laminates which are reinforced with AS-4 carbon fibers of volume fractions in the range of 65-69% has... 

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