- author = "Alaa Al-Mosawe",
- title = "Investigation of the performance of cracked steel members strengthened with carbon fibre reinforced polymers under impact loads",
- school = "Faculty of Science, Engineering and Technology, Swinburne University of Technology",
- year = "2016",
- address = "Melbourne, Australia",
- keywords = "genetic algorithms, genetic programming, CFRP, Fe",
-
URL = "
http://hdl.handle.net/1959.3/414765",
-
URL = "
https://researchbank.swinburne.edu.au/file/0cca0b0c-0219-4cb0-b0d3-b33bcdb159a8/1/Alaa%20Al-Mosawe%20Thesis.pdf",
- size = "224 pages",
-
abstract = "Generally, steel structures are subjected to different
types of loadings during their life-time. Over time
these structures sustain fewer loads than those for
which they were designed. The reduction in structural
capacity might occur as a result of various parameters,
including aging, changes in use, increases in applied
loads, and as a result of environmental effects causing
corrosion. These structures need to be strengthened or
repaired in order to be able to carry the different
applied loads.
Carbon fibre reinforced polymers (CFRPs) are a new method of strengthening, the use of which has grown in the last few decades. This method of strengthening has attracted structural engineers due to its ease of application, light weight and very high tensile strength. The bond between CFRP and steel members is the main issue in understanding the bond behaviour. This thesis presents the effect of impact loading on the bond behaviour of CFRP-steel double strap joints.
The results of comprehensive experimental tests are presented in this project on the basis of testing large numbers of CFRP-steel double strap joints under both static and dynamic loadings. Another series of tests was conducted to investigate the mechanical properties of the composite material itself. The mechanical properties were investigated under different loading rates, starting from quasi-static loading at 2mm/min, to impact loadings of 201000mm/minute, 258000mm/minute and 300000mm/minute. The experimental results showed that loading rate has a significant effect on the material properties, and a significant increase was shown in tensile strength and modulus of elasticity.
The results of another series of tests are presented in this thesis. A number of CFRP-steel double strap joints were prepared and tested under quasi-static loads. Three different types of CFRP modulus (low modulus 165 GPa, normal modulus 205GPa and ultra-high CFRP modulus 460 GPa) were used, to study the effect of CFRP modulus on the bond behaviour between steel and CFRP laminates. In order to investigate the effect of CFRP geometry on the bond properties, two different CFRP sections were used (20 by 1.4mm and 10 by 1.4mm). The results showed a significant influence on the bond strength, strain distribution along the bond, effective bond length and failure mode for specimens with different CFRP modulus. The results also showed that a small CFRP section is sensitive to any little movement.
Further tests were also conducted on CFRP-steel double strap specimens with different CFRP moduli under high impact loading rates. The load rates used in this project were 201m per minute, 258m per minute and 300m/min. The aim of this test was to find the degree of joint enhancement under dynamic loadings compared to quasi-static loads. The results showed a significant increase in load-carrying capacity, and strain distribution along the bond. However, a significant decrease in the effective bond length under impact loads was observed compared to quasi-static testing. Different failure modes were shown compared to specimens tested under quasi-static loadings.
Finite element analysis was conducted in this research to model the CFRP-steel double strap joint under both quasi-static and dynamic loads. The individual components of the joint (CFRP laminate, Araldite 420 adhesive and steel plates) were first modeled and analysed under the four loading rates. The CFRP-steel double strap joints were modelled using non-linear finite element analysis using the commercial software ABAQUS 6.13. The results showed good prediction of material properties and joint behaviour using non-linear finite element analysis, and the results of tensile joint strength, strain distribution along the bond, effective bond length and failure modes were close to those tested experimentally.
This thesis also shows a new formulation of CFRP-steel double strap joints using genetic programming; the data from the experimental and numerical analysis were analysed using genetic programming software. Three different parameters were used: bond length, loading rate and the CFRP modulus. The outcomes of this analysis are showing an expression tree and a new equation to express the bond strength of these types of joints. The results are assumed to be used for the range of parameters used as input data in the programming.
Finally, some suggestions on future work to continue the investigation of the bond behaviour between CFRP and steel in the double strap joints are provided.",
- notes = "supervisor: Riadh Al-Mahaidi",
