Matrix shear yield strength

Apart from the elastic stress transfer at the perfectly bonded interface, another important phenomenon that must be taken into account is the stress transfer by friction, which is governed by the Coulomb friction law after the interface bond fails. Furthermore, matrix yielding often takes place at the interface region in preference to interfacial debonding if the matrix shear yield strength, Xm is significantly smaller than the apparent interface bond strength, tb. It follows thus... 

Critical fiber length—dependence on fiber strength and diameter and fiber-matrix bond strength (or matrix shear yield strength)... 

Tc Fiber-matrix bond strength or matrix shear yield strength... 

Critical fiber length = [Ultimate or tensile strength times fiber diameter/2] times the fiber-matrix bond strength or the shear yield strength of the matrix— whichever is smaller... 

The mechanical properties, fiacture stress, fiacture strain, yield stress, and modulus, were measured (67) for doses up to 100 Mrads. Fracture strain was found to increase with dosage but shear yield strength decreased. Decreases averaging roughly 50% were noted for the other properties. Therefore, it is evident that the -radiation produces a predominance of chain scission over crosslinking in the epoxy. It was concluded that irradiation does not have much effect on the graphite fibers but that it degrades mechanical properties of the epoxy matrix. 

Direct measurement of inter facial shear strength by single fibre fragmentation technique 46 MPa. 2. Shear yield strength of matrix 48 MPa. ... 

Consider the peak stress that can be carried by a chopped-fibre composite which has a matrix with a yield strength in shear of d (d = jd ). Figure 25.4 shows that the axial force transmitted to a fibre of diameter d over a little segment 8x of its length is... 

When ABS is compared to HIPS at comparable stress amplitudes, fatigue lifetimes are several decades higher. Several factors are involved. First, tensile strength and modulus of the SAN matrix are increased compared to values for the PS matrix. Secondly, the SAN matrix is more resistant to crazing and thirdly, the primary mode of deformation for ABS appears to be shear yielding rather than crazing. 

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