Thermomechanically micromechanical modeling of prestressed concrete reinforced with shape memory alloy fibers

Freed, Yuval; Aboudi, Jacob; Gilat, Rivka

doi:10.1088/0964-1726/16/3/019

Cited by 10 publications

(13 citation statements)

References 24 publications

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“…Based on their experiments, for cementious materials, the temperature should not exceed 95 degrees Celsius to avoid thermally induced microcracking in the mortar matrix. Freed et al (2007) varied the SMA prestressing fibers from zero to two percent by volume and as expected, the breaking stress increased with more fibers. They also concluded that the SMA samples took more stress than with traditionally prestressed samples and that the coefficient of thermal expansion between the concrete and the SMA is negligible.…”

Section: Uses Of Nitinol For Prestressing Concretesupporting

confidence: 62%

Prestressing Concrete with Shape Memory Alloy Fibers

Orvis¹

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In partial fulfillment of the requirements for the degree of Abstract Prestressing Concrete with Shape Memory Alloy Fibers Skye Mikaella OrvisConcrete is considerably stronger in compression than it is in tension. When cracks form in concrete members, the flexural stiffness of the member decreases and the deflection increases which increases the overall size of the member. Prestressing concrete remedies this problem by inducing a compressive stress in the concrete thereby reducing the net tension in the member and increasing the load required to crack the member. Traditional prestressing is generally limited to large, straight members. During the last decade, shape memory alloys (SMA) have become more prevalent in engineering and civil engineering applications. The shape memory effect refers to the contraction of the SMA when it is heated to its austenite phase. When a prestrain is induced in the SMA, it can be recovered when it goes through the phase change. Nitinol, a NiTi shape memory alloy was used in this research. Thin, steel cables were also tested to provide a comparison. Two different Nitinol alloys were studied in this research. The alloy M wires were elongated to 8% stain while the alloy X wires were prestrained by the manufacturer. The wires were cast into thin concrete beams and once cured, the beams were heated and a phase change from martensite to austenite occurred in the Nitinol. As a result, the Nitinol contracted and compressed the concrete. The SMA fibers are randomly oriented and allow prestressing to occur along all three axis. This is ideal for thin, curved specimens. Third-point bending tests showed that the SMA fibers prestressed the concrete and upon reheating the cracked specimens, the shape memory effect provides partial crack closure.

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Section: Uses Of Nitinol For Prestressing Concretesupporting

confidence: 62%

Prestressing Concrete with Shape Memory Alloy Fibers

Orvis¹

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“…The effects of the inelastic deformation of fibers on the overall behavior of unidirectional NiTi composite were numerically examined for loading and unloading in the longitudinal direction using the developed three-dimensional model. The high-fidelity generalized method of cells [1] was used extensively by Freed, Aboudi, and coworkers to study a number of different SMA composite systems while incorporating full thermomechanical coupling [143,144,140,142,141]. Of particular interest was the ability of prestressed SMA fibers to strengthen concrete materials considering both a damage-based [143] and coupled damage-plastic [140] formulation for the concrete phase.…”

Section: Full-field Approachesmentioning

confidence: 99%

“…The high-fidelity generalized method of cells [1] was used extensively by Freed, Aboudi, and coworkers to study a number of different SMA composite systems while incorporating full thermomechanical coupling [143,144,140,142,141]. Of particular interest was the ability of prestressed SMA fibers to strengthen concrete materials considering both a damage-based [143] and coupled damage-plastic [140] formulation for the concrete phase. Through these investigations, it was shown that fiber shape was insignificant if non-zero thermal expansion coefficients were used and higher activation temperatures lead to larger beneficial prestresses [143].…”

Section: Full-field Approachesmentioning

confidence: 99%

“…Of particular interest was the ability of prestressed SMA fibers to strengthen concrete materials considering both a damage-based [143] and coupled damage-plastic [140] formulation for the concrete phase. Through these investigations, it was shown that fiber shape was insignificant if non-zero thermal expansion coefficients were used and higher activation temperatures lead to larger beneficial prestresses [143]. Yield surfaces of the resultant material were also constructed and in the damage-plasticity case it was demonstrated that increases in the activation temperature produced decreased residual plastic strain [140].…”

Section: Full-field Approachesmentioning

confidence: 99%

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Review and perspectives: shape memory alloy composite systems

et al. 2015

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Following their discovery in the early 60's, there has been a continuous quest for ways to take advantage of the extraordinary properties of shape memory alloys (SMAs). These intermetallic alloys can be extremely compliant while retaining the strength of metals and can convert thermal energy to mechanical work. The unique properties of SMAs result from a reversible difussionless solid-to-solid phase transformation from austenite to martensite. The integration of SMAs into composite structures has resulted in many benefits, which include actuation, vibration control, damping, sensing, and selfhealing. However, despite substantial research in this area, a comparable adoption of SMA composites by industry has not yet been realized. This discrepancy between academic research and commercial interest is largely associated with the material complexity that includes strong thermomechanical coupling, large inelastic deformations, and variable thermoelastic properties. Nonetheless, as SMAs are becoming increasingly accepted in engineering applications, a similar trend for SMA composites is expected in aerospace, automotive, and energy conversion and storage related applications. In an effort to aid in this endeavor, a comprehensive overview of advances with regard to SMA composites and devices utilizing them is pursued in this paper. Emphasis is placed on identifying the characteristic responses and properties of these material systems as well as on comparing the various modeling methodologies for describing their response. Furthermore, the paper concludes with a discussion of future research efforts that may have the greatest impact on promoting the development of SMA composites and their implementation in multifunctional structures.

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“…This model is capable to accurately predict the global (macroscopic) behavior of the composite by properly taking into account the detailed interaction between the various constituents. It may be noted that the HFGMC framework was successfully employed for different applications of shape memory alloy and shape memory alloy composites in the past (see for example, Aboudi and Freed, 2006;Freed et al, 2007;Freed and Aboudi, in press, 2008) and therefore this micromechanical method is chosen in this investigation.…”

Section: Introductionmentioning

confidence: 99%

Micromechanical prediction of the two-way shape memory effect in shape memory alloy composites

Freed

Aboudi

2009

International Journal of Solids and Structures

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Keywords:Fiber reinforced High-fidelity generalized method of cells Homogenization Micro-mechanics Modeling Shape memory Thermal loading Two-way shape memory effect a b s t r a c tThe two-way shape memory effect in monolithic shape memory alloys has been widely investigated both theoretically and experimentally. In the present study, this effect is analyzed for shape memory alloy composites by employing a micromechanical model. To this end, the responses of polymeric matrix and metal matrix unidirectional composites with embedded shape memory alloy fibers are determined. For the polymeric matrix composite, the effect of axial, transverse and shear loadings as well as the fiber volume fraction on the resulting two-way shape memory behavior are studied. The local distributions of stresses among the shape memory alloy fiber and epoxy matrix in the low-and high-temperature shapes of the composite are also investigated. Two training procedures that generate the two-way shape memory effect in the metal matrix composite are offered. The present analysis shows that the two-way shape memory effect in the chosen type of metal matrix composite is not as useful as in the polymeric matrix one. Finally, for a polymeric matrix composite that is subjected to a transverse normal loading, the effect of imperfect bonding between the shape memory alloy fibers and the neighboring matrix is investigated.

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Thermomechanically micromechanical modeling of prestressed concrete reinforced with shape memory alloy fibers

Cited by 10 publications

References 24 publications

Prestressing Concrete with Shape Memory Alloy Fibers

Prestressing Concrete with Shape Memory Alloy Fibers

Review and perspectives: shape memory alloy composite systems

Micromechanical prediction of the two-way shape memory effect in shape memory alloy composites

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