13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- mK is taken. While noting that 0 0 δΠ = , enforcing the first variation with respect to mK to vanish results in { } 1 m t H− = − K Rv f (10) Substituting for mK in the expression for the total potential, and enforcing the first variation of the total potential to vanish results in the nodal equations of equilibrium for the global element as { } * 0 T t s δΠ= − − = v K v F f (11) leading to * t s = + K v F f (12) in which sK and t F are defined as 1 T s − = K G H G and 1 t T t − = F G H f . The vector * f represents the internal loading vector at a node common to both the global and conventional elements. If a node is free of conventional elements, the components of the load vector represent the external force components. The vector t F represents the reaction force that suppresses the deformation, resulting from thermal loading only, at the common nodes of global and conventional elements. 3. Experiment results Fig. 2 shows a fiber metal laminate specimen with splices in interrupted aluminum layer edges. The materials comprising the specimen are aluminum, woven glass fiber reinforced composite and epoxy resin. Their elastic properties and coefficients of thermal expansion are listed in Tables 1 and 2. The thicknesses of aluminum layer and epoxy resin are all 1mm, the thickness of woven glass fiber reinforced composite varies as H=1, 2, 3, the width of splices vary as w=0.5, 1, 2, 3, 4, 5, 6, and the width of all layers are 20mm. Co-cured fiber metal laminate specimens were fabricated under the manufacture’s recommended cure cycle for the composite material, and Fig. 3 illustrates the fabrication process. Figure 2. Dimensions of the spliced fiber metal laminate Shimadzu EHF-EM electric-fluid serving tensile testing machine are used to test tension force, and Fig. 4 shows the tensile test apparatus. The load-displacement response curve obtained from the tensile test is linear until crack initiates at the splice, as shown in Fig. 5. Typical fractured fiber metal laminate specimens are shown in Fig. 6,by inspecting the fracture process, it is found that interface cracks initiate at the interface edge of the epoxy resin and the aluminum and propagate along the interface. Load bearing capacities Fc of the spliced fiber metal laminate specimens with varying splice width and fiber layer thickness are listed in Table 3. Experiment results show that, critical fracture load Fc increases with decreasing of splice width w, and decreases with increasing Epoxy resin Aluminum Composite w 200 1 1 H
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