Effect of Adhesive Thickness on Bond Behavior of

Effect of Adhesive Thickness on Bond Behavior of Carbon Fiber Sheet under Static and Fatigue Load Hokkaido Univ. Tamura Hiroya

The outline of the study Background ・adhesive thickness is controlled by conditions at the surface concrete. ・the few studies of adhesion characteristics in cyclic loading. Object To get deeper insight into the effect of varying adhesive thickness under static and fatigue loading.

Experimental Property specimen static concrete compressive strength 30 MPa slump 12 cm sheet property ST-02 0. 2 mm ST-11 Elastic modules 245 GPa ST-21 ST-32 FA-03 ST-03 ST-12 593 GPa FA-01 ST-01 0. 333 mm Elastic modules thickness resin property fatigue 1 mm 2 mm 3 mm 0. 2 mm FA-04 FA-05 FA-11 FA-12 FA-13 1 mm FA-14 FA-31 FA-32 FA-33 FA-34 3 mm

Specimen style attaching work ① making divider ② pouring resin 400 ③ attaching CFS 60 400 60 100 unbonded area 50 200 150 100

Test Equipment prepared according to Osaka University’s bending machine test setup Load Beam Distributing 855 specimen advantage Hinge H steel 600 1200 n To cancel out bending moment on sheet n To be easy to calculate working pull out strength on sheet

Static Test Result Pullout Strength n Increasing with adhesive thickness n The rate of increase step down Dai et al. ’s model s e r or d n po C This is experimental formula the function of resin thickness

Static Test Result Pullout strength is increasing with adhesive thickness Why correlation? Thickness increase thickness 0. 2 mm Effective bond length increase Local bond stress decrease Pullout strength increase thickness 2 mm

Definition - Effective Bond Length ne li 100% 5% line sheet stress distribution It is considered that 5% of maximum bond stress is active Bond stress distribution The effective bond length is 90 mm

Effective Bond Length Effective bond length is very different between 0. 2 mm specimens and the others. Adhesive thickness ST-01 ST-02 100 mm 0. 2 mm ST-12 ST-21 ST-32 120 mm 90 mm ST-03 ST-11 Effective bond length 1 mm 2 mm 3 mm 180 mm 180 mm Pattern like pull out strength

Fatigue Test Result – fatigue life In fatigue loading level Fatigue life decrease with adhesive thickness 1 mm and 3 mm specimens are extremely low, compare to 0. 2 mm specimens. In fatigue loading The fatigue life is closing each other as fatigue life decrease. 0. 2 mm specimen’s fatigue life that is lower than 22 k. N is the longest

Fatigue Test Result － effective bond length In static test The specimen of 0. 2 mm thick are lower effective bond length than the other. t = 0. 2 mm Static test In fatigue test Static test Fatigue test Effective bond lengths of 0. 2 mm specimens increase therefore Fatigue test Fatigue life of 0. 2 mm specimen get to be long

Conclusion 1 n the static test, the pullout bond strength increased with the adhesive thickness because the effective bond length increased. 2 The effects of adhesive thickness were as predicted by Dai et al’s model. 3 In the fatigue test, the fatigue life in the case of 0. 2 mm adhesive thickness became longer because the effective bond length became longer in comparison with the thicker adhesive cases.

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Breaking pattern thickness 0. 2 mm thickness 1～ 3 mm Thick resin causes to break on resin layer, not concrete surface. Capability that difference in thickness may be the reason of the result in fatigue.

Breaking pattern Thickness 3 mm thickness 0. 2 mm

Object of Pretest for master thesis Steel slab is reinforced by UFC Both Steel and UFC have high strength, therefore can design by only two value, adhesive thickness and elastic modules. I choose adhesive thickness as the experimental value to Compare to graduation thesis Constitutive law of adhesion of different material (FRP-concrete, UFC-steel)

UFC is … material cement Steel fiber water Silica fume High strength High density Compressive strength is Tensile strength is fine aggregate Silicate sand x 5 x 3 Dispersion of crack This property can avoid brittle failure High durability against… l chemical attack l Salt attack l Freezing and thawing

The way of control adhesive thickness Polystyrene is used to encircle the area to be bonded to the intended adhesive thickness 60 400 UFC 140 10 200 50 Polystyrene Steel formed H 100