Failure tearing mode

Figure 11.9 The three modes of failure (a) opening mode, or mode I, characterized by (b) sliding mode, or mode II, (c) tearing mode, or mode HI,...

Susceptibility to interlaminar failure is a major weakness of advanced laminated composite materials. It can occur by in-plane shearing (i.e., sliding) (mode II). and out-of-plane shearing (i.e.. tearing) (mode III) as well as by tensile (mode I) deformation. Mode II loading is of particular interest, as values have been shown to correlate with compression after impact data [142.143]. which is required for such purposes as civil aircraft certification. 

Figure 1 shows a compact tension specimen in which a starter crack propagated at a controlled rate such that the test could be stopped prior to specimen failure. Whitened areas above and below the fracture surfaces are a result of particle cavitation. This particular material was a flexibilized vinyl ester containing a rubber particulate phase. The large volume of material involved in the fracture process resulted in high toughness and a ductile tearing mode of fracture as opposed to the brittle fracture mode of the base resin. 

Brittle solids fail in one of three possible modes, shown in Fig. 5.47. In mode I (the opening mode), both the crack plane and the direction of propagation are normal to the applied tension. In mode II (the sliding mode), a tensUe shear acts to slide the fracture planes over each other in the direction of stress. Mode IE (the tearing mode) is also a shear failure, except that the shear causes the fracture to propagate normal to the stress. Corresponding to these three modes, a material has three critical values of the stress intensity factor and... 

The vibratory mode most frequently encountered is of the plate type and involves either the shroud or the disc. Fatigue failure generally originates at the impeller outside diameter, adjacent to a vane often dne to the vibratory motion of the shroud or disc. The fatigue crack propagates inward along the nodal line, and finally a section of the shrond or disc tears out. 

Scenarios— for each chenucal/mode of transport, three release sizes will be analyzed for a breach of the transportation container small hole (i.e., shearing of a valve coimection), tear (i.e., punctnre of the container), and catastrophic failure (i.e., large breach of the container), and are designated as small, medium, and large releases during the analysis... 

Figure 13.35 Basic modes of failure of structural materials ( ) opening or tensile mode (II) sliding or in-plane shear mode (III) tearing or antiplane shear mode.

There are three main types of failure by crack propagation as shown in Figure 10.3 1 (opening), II (sliding), and III (tearing). In real elements made with composite materials and subjected to external load, all modes appear in different combinations and it is not completely clear how to deal with that situation. The models proposed at present seem to still be dependent on the scale if in macro scale the tests executed according to these three modes are possible the obtained results characterize only the effects in the same scale with mean values of some correcting parameters. On lower scales probably all modes appear simultaneously or at least Modes I and II act conjointly. The mixed-mode fracture parameters may be calculated for linear elastic materials within the frames of LEFM, but their direct application to the cement-based composites is questioned. The considerations below are partly based on the paper by Brandt and Prokopski (1990). 

FIGURE 5.47 Three modes of failure in brittle materials a) opening, b) sliding, (c) tearing. 

Ductile failures are characterized by gradual tearing of the surfaces when applied forces exceed the yield strength of the material. For the crack resulting from the dutrile mode... 

---