| In order to explore the application of adhesion technique in the automobile manufacture,a cooperative research project between Zhengzhou University and General Motors Corporation was carried out with the support of GM collaborative Funding.The key task in this project is to decreasing the curing temperature of commercial Henkel 5089 adhesive.In this study,the effect of the addition of curing agent(C1,C2)or/and curing accelerator(CA1,CA2)on the curing temperature of Henkel 5089 adhesive was investigated in detail by the measurement of shear strength of adhesive-bonded aluminum AA6061 joints with different modified Henkel 5089 adhesives.The results showed that the curing temperature of Henkel 5089 adhesive could be apparently decreased with the sole addition of curing agent C1,C2,or curing accelerator CA1.Furthermore,the degree of the decreasing effect was closely associated with the amount of additives.In the range of 1.0%-4.0wt.%(wt.%,weight percentage,the same as following)of additives,lower curing temperature can be obtained with larger amount of additives.For the same amount of additives,the effect of curing agent C2 on lowering curing temperature was better than that of C2.The failure mode of the adhesive-bonded joints was mainly mixed fracture.The orthogonal tests showed that a better bonding strength at low temperatures could be obtained if the curing agent and curing accelerator were jointly added to Henkel 5089 adhesive.Better adhesive performance can be observed for the modified Henkel 5089 adhesive with joint addition of the following:(1)1.0% CA1+4.0% C1,(2)4.0% CA2+1.0% C1,(3)4.0% CA2+2.5% C2.The shear strength of the modified Henkel 5089 adhesive-bonded aluminum AA6061 joints cured at 130 oC for 20 min was equivalent to that of Henkel 5089 after cured at 177 oC for 20min(26.14±0.52MPa).In addition,a slightly lower joint strength can be obtained if the total content of curing agent and curing accelerator was too high(?6.5%).The measurements of the shear strength of joints showed that the modified Henkel 5089 adhesive with 1.0% CA1+4.0% C1,4.0% CA2+1.0% C1,or 4.0% CA2+2.5% C2 can be cured within 20 min in the curing temperature range of 100 oC to 120 oC.Although the joint strength of modified adhesive was slightly lower than that of Henkel 5089 adhesive cured at 177 oC for 20 min,it was still above 20 MPa,which can satisfy the requirement of the high strength adhesive-bonding joints in automobile manufacture(?16MPa).The shear strength of adhesive-bonded joints cured at room temperature showed that the modified Henkel 5089 adhesive with 4.0% CA2+2.5% C2 could be cured at room temperature.The shear strength of this modified Henkel 5089 adhesive-bonded joint cured at room temperature increased rapidly in the first two days,then increased to a stable value(~21MPa)with further increasing curing time,which was comparable to that of cured at 120 oC for 20 min.The joint strength(~21MPa)of the modified Henkel 5089 adhesive was much higher than that of the commercial Lord Fusor 320/322 structural adhesive(~11MPa)which was also cured at room temperature.The results showed that the modified Henkel 5089 could be used as a room temperature curing adhesive in automobile manufacturing.For other two modified Henkel 5089 adhesives,the shear strength of joints cured at room temperature for 10 days was still apparently lower than that cured at 100oC-150oC(~ 20MPa),which cannot satisfy the requirement of the high strength adhesive-bonding joints(?16MPa)in automobile manufacture.The comprehensive results showed that the modified Henkel 5089 with 4.0% CA2+2.5% C2 have the best adhesive performance among the three modified adhesives derived from the orthogonal tests.For the curing time of 20 min,the curing temperature of the modified Henkel 5089 adhesive can be effectively reduced to 100 oC with sacrificing some shear strength(~6MPa).The modified adhesive can even be cured at room temperature if the curing time is long enough.The obtained joint strength was about 21 MPa,which satisfy the requirement of the high strength adhesive-bonding joints(?16MPa)in automobile manufacture. |
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