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Figure from:Generalized shape optimization of three-dimensional structures using materials with optimum microstructures

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Figure 1: Tensile behavior of SIMCON and SIFCON

Figure 1 Tensile behavior of SIMCON and SIFCON

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Table 1 summarizes various types of coupled behavior between mechanical, ther- mal and electromagnetic phenomena. The first five rows denote linear coupling behavior between flux vector 7 and field vector Z or scalar 0 while the last four are for non-linear or non-colinear coupling behavior. We have recently established the micromechanics modeling of a smart composite with linear coupling behavior by extending the Eshelby’s model for uncoupled behavior where an example of piezo- electric composite was used. The prediction of coupling coefficients of the composite explain well the experimental results. The Eshelby’s model can also be applicable tc t t he case of a composite with shape memory alloy (SMA) fibers. We have predicted he compressive stress in the matrix material of SMA composite which was given initial prestrain ep at room temperature and then subjected to temperature increase beyond austenitic finish temperature (A+). This compressive stress was a dominant contributor to enhance the tensile properties of TiNi SMA fiber/Al matrix compos- ites (stress-strain curve and fatigue resistance) and of TiNi SMA fiber/epoxy matrix “Smart composites” should be distinguished from ordinary composites which are for its primary use as a structural material with high specific mechanical properties. Definition of a smart composite is that it can exhibit a desired function in given environment such as control of a desired shape, induction of desired internal stress and strain. The key element for designing such a smart composite is to use “smart material” as a reinforcement which exhibits coupled behavior where the coupling takes place between any combination of mechanical, thermal and electromagnetic behavior. In this talk, coupled behavior of various smart materials will be stated first, followed by micromechanics modeling of several smart composites which consist of a smart materials as the key constituent and matrix material.
Table 1 summarizes various types of coupled behavior between mechanical, ther- mal and electromagnetic phenomena. The first five rows denote linear coupling behavior between flux vector 7 and field vector Z or scalar 0 while the last four are for non-linear or non-colinear coupling behavior. We have recently established the micromechanics modeling of a smart composite with linear coupling behavior by extending the Eshelby’s model for uncoupled behavior where an example of piezo- electric composite was used. The prediction of coupling coefficients of the composite explain well the experimental results. The Eshelby’s model can also be applicable tc t t he case of a composite with shape memory alloy (SMA) fibers. We have predicted he compressive stress in the matrix material of SMA composite which was given initial prestrain ep at room temperature and then subjected to temperature increase beyond austenitic finish temperature (A+). This compressive stress was a dominant contributor to enhance the tensile properties of TiNi SMA fiber/Al matrix compos- ites (stress-strain curve and fatigue resistance) and of TiNi SMA fiber/epoxy matrix “Smart composites” should be distinguished from ordinary composites which are for its primary use as a structural material with high specific mechanical properties. Definition of a smart composite is that it can exhibit a desired function in given environment such as control of a desired shape, induction of desired internal stress and strain. The key element for designing such a smart composite is to use “smart material” as a reinforcement which exhibits coupled behavior where the coupling takes place between any combination of mechanical, thermal and electromagnetic behavior. In this talk, coupled behavior of various smart materials will be stated first, followed by micromechanics modeling of several smart composites which consist of a smart materials as the key constituent and matrix material.
Figure 1: Comparison between the analytical and experimental results
Figure 1: Comparison between the analytical and experimental results
Figure 1: Failure mode of bond-type anchor Bond-type anchors fasten the structures to massive concrete or rocks by its bonding strength on the surfaces of anchor bolts. They are so called post-installed systems and have been used often in the retrofit of masonry or concrete structures. The recent development of construction technology has diversified the applicability, and now in some cases they are used in new construction sites. The bond-type anchor, unlike a usual headed anchor, exhibits complex failure modes. If we preclude the trivial failure by the yielding of anchor bolt, the potential failure modes of the bond- type anchor are classified as a) bond failure, b) cone-failure, and c) mixed bond-cone ailure depending on material and geometric conditions. (Fig. 1) When the bonding resistance on the bolt surface is small, the anchor fails by pulling out and when the bond between the bolt and the surroundings are perfect, only cone failure is possible and permissible. The usual failure mode, therefore, is somewhere between these two extreme cases, resulting in the complex mixed bond-cone failure. Because of this complexities, the rational design method of the bond type anchor is still to be sought for. In a simple case, we have already proposed the method to estimate the strength and the failure mode. Among the various cases to be contemplated, in this work, we focus the effect of free edge on the pull-out strength with the help of inear fracture mechanics.
Figure 1: Failure mode of bond-type anchor Bond-type anchors fasten the structures to massive concrete or rocks by its bonding strength on the surfaces of anchor bolts. They are so called post-installed systems and have been used often in the retrofit of masonry or concrete structures. The recent development of construction technology has diversified the applicability, and now in some cases they are used in new construction sites. The bond-type anchor, unlike a usual headed anchor, exhibits complex failure modes. If we preclude the trivial failure by the yielding of anchor bolt, the potential failure modes of the bond- type anchor are classified as a) bond failure, b) cone-failure, and c) mixed bond-cone ailure depending on material and geometric conditions. (Fig. 1) When the bonding resistance on the bolt surface is small, the anchor fails by pulling out and when the bond between the bolt and the surroundings are perfect, only cone failure is possible and permissible. The usual failure mode, therefore, is somewhere between these two extreme cases, resulting in the complex mixed bond-cone failure. Because of this complexities, the rational design method of the bond type anchor is still to be sought for. In a simple case, we have already proposed the method to estimate the strength and the failure mode. Among the various cases to be contemplated, in this work, we focus the effect of free edge on the pull-out strength with the help of inear fracture mechanics.
Figure 2: Bond-type anchor near a free edge
Figure 2: Bond-type anchor near a free edge
Figure 4: Pull-out strength of a bond-type anchor near a free edge Figure 3: Failure mechanism of a bond-type anchor
Figure 4: Pull-out strength of a bond-type anchor near a free edge Figure 3: Failure mechanism of a bond-type anchor
Figure 3: Relationship between o/(Hy + 120) and \/area. Letters correspond to the materials given in reference[3, 4]. Figure 1: Relationship be- tween the maximum stress intensity factor Kymax and area for various surface cracks[1, 2].
Figure 3: Relationship between o/(Hy + 120) and \/area. Letters correspond to the materials given in reference[3, 4]. Figure 1: Relationship be- tween the maximum stress intensity factor Kymax and area for various surface cracks[1, 2].
Figure 3: Tensile behavior of pre-cracked speci- mens with different debonded fiber lengths
Figure 3: Tensile behavior of pre-cracked speci- mens with different debonded fiber lengths
Figure 1: Definition of the problem
Figure 1: Definition of the problem
Figure 4: Curved interacting growth of fiber- end cracks Figure 2: Avoidance of edge cracks
Figure 4: Curved interacting growth of fiber- end cracks Figure 2: Avoidance of edge cracks