Dynamic behaviour of composite sandwich beams and plates with debonds

PhD Thesis


Jayatilake, Indunil Nayanakanthi. 2017. Dynamic behaviour of composite sandwich beams and plates with debonds. PhD Thesis Doctor of Philosophy. University of Southern Queensland. https://doi.org/10.26192/5bf78a50f93e5
Title

Dynamic behaviour of composite sandwich beams and plates with debonds

TypePhD Thesis
Authors
AuthorJayatilake, Indunil Nayanakanthi
SupervisorKarunasena, Karu
Institution of OriginUniversity of Southern Queensland
Qualification NameDoctor of Philosophy
Number of Pages223
Year2017
Digital Object Identifier (DOI)https://doi.org/10.26192/5bf78a50f93e5
Abstract

Fibre Reinforced Polymer (FRP) composites are continuing to gain prominence in structural as well as non-structural applications all over the world due to their outstanding properties such as high strength to weight ratio, corrosion resistance, good thermal performance, anti-fire performance and reduction of carbon dioxide emissions both through its method of production and their effective thermal insulation qualities. The increased popularity and demand for FRP composites have spurred research efforts in both academia and civil construction industry.

A composite sandwich structural element can be made-up by attaching two thin and stiff skins to a lightweight and thick core, which serves as a building block for constructing laminated structural sandwich composites for civil engineering applications. A structural composite multilayer beam or plate can be manufactured by gluing two or more composite sandwiches together to form a laminated composite. An Australian manufacturer has fabricated a new generation structural Glass Fibre Reinforced Polymer (GFRP) sandwich panel made from E-glass fibre skin and a high strength modified phenolic core for civil engineering applications, the outstanding features of the sandwich material being high strength to weight ratio, good thermal insulation and termite resistance. These features offer the composite panel a wide range of applications in Australian construction industry as structural elements such as beams, slabs, bridge decks and railway sleepers.

While sandwich composite construction has some great benefits, the behaviour of sandwich structures containing damage is much more complex and one of the major factors limiting the optimum usage of the same. Although perfect bond between the skin and the core is a common assumption, an important issue that needs to be considered in using a composite beam or slab is the development of debonding between the skin and the core, which is a predominant damage mode of these sandwiches. Interlayer debonding or delamination is also a predominant form of damage phenomenon in laminated composites, which can often be pre-existing or can take place under service conditions. Debonding and delamination cause significant changes in the vibration parameters, such as natural frequencies and mode shapes of structures leading to serviceability issues related to deflection limits. During the design stages of FRP composite structures, it is vital to identify how the global response of these structures will be affected by skin-core debonding and interlayer delamination.

Even though the dynamic behaviour of undamaged sandwich panels is the subject of extensive research, papers reported on the dynamic behaviour of sandwich panels with debonding are less presented in the literature. Specifically, knowledge on seismic behaviour of composites with debonds is severely limited. Further research is therefore needed into investigation of the dynamic behaviour of debonded composite structural elements to gain wider acceptance of composites by the structural composite field around the globe. Finite element method is particularly versatile and effective in the analysis of complex structural behaviour of the composite structures. The use of dynamic analysis methods helps the engineer to better understand the behaviour of a structure subjected to an earthquake.

This research deals with the investigation of the influence of debonding on the dynamic characteristics of novel GFRP beams and plates by finite element based numerical simulations and analyses using STRAND7 finite element (FE) software package. The research approach is to develop a three dimensional computer model and conduct numerical simulations to assess the dynamic behaviour. The FE model developed has been validated with published experimental, analytical and numerical results for fully bonded as well as debonded beams and slabs. Dynamic seismic response investigation of structures containing GFRP slab panels with debonds subjected to a probable earthquake loading is also incorporated. The influence of various factors such as debonding size, location of debonding, boundary condition of the structural member and the effect of multiple debonding has been delineated with the aid of an extensive parametric investigation and comparative analyses.

Generally it was evident from all the analyses that debonding and interlayer delamination cause reduction in magnitudes of natural frequency. Moreover, some vibration modes and accordingly the mode shapes are also noticeably changed. It is generally observed that higher natural frequencies and mode shapes are more influenced by the presence of debonding. Yet there are exceptions to this trend depending on how severely the local modes are affected by debonding. It is observed that the associated mode shapes explain the causes of these inconsistencies. Furthermore, the results show that the presence of relatively small debonding or delamination has an insignificant effect on the natural frequencies and associated mode shapes. The results also suggest that fastening the delamination region is an effective corrective measure in decreasing the natural frequency variation, hence improving its dynamic performance compared to the delaminated panel.

To sum up, the results suggest that debonding and delamination predominantly leads to reduction of the natural frequencies and modifying the modes of vibrations thus altering the mode shapes as well, resulting in dramatic changes in dynamic characteristics when extents of debonding are large. The more the supports are restrained, the greater the influence on free vibration characteristics. Most importantly, the findings demonstrate the feasibility of non-destructive methods to detect debonding and delamination damage in practical composite structures. The results of the seismic study show that the seismic performance of the considered buildings is unresponsive to small percentages of debonding of the GFRP slab panels. An existence of extensive percentage of debonding causes a slight increase in the maximum vertical displacement and reduction of natural frequencies of the buildings due to loss of stiffness occurring due to debonding.

The results of this study will offer engineers and designers a better understanding of the influence of debonding and delamination on the dynamic performance of FRP composites in general, in addition to its direct application to Australian composite industry. Finally, the study provides valuable insights into the seismic behaviour of composite slabs with debonding thus facilitating the actual application of these findings in worldwide composite industry.

Keywordsfibre reinforced polymer composites; FRP; composite sandwich beams
ANZSRC Field of Research 2020401609. Polymers and plastics
Byline AffiliationsCentre of Excellence in Engineered Fibre Composites
Permalink -

https://research.usq.edu.au/item/q45v7/dynamic-behaviour-of-composite-sandwich-beams-and-plates-with-debonds

Download files


Published Version
Jayatilake_2017.pdf
File access level: Anyone

  • 1438
    total views
  • 180
    total downloads
  • 4
    views this month
  • 1
    downloads this month

Export as

Related outputs

3D Numerical Simulation and Dynamic Analyses of Debonded GFRP Composite Slabs
Jayatilake, I. N. and Karunasena, W.. 2020. "3D Numerical Simulation and Dynamic Analyses of Debonded GFRP Composite Slabs." 25th Australasian Conference on the Mechanics of Structures and Materials (ACMSM25). Brisbane, Australia 01 - 01 Dec 2018 Singapore. Springer. https://doi.org/10.1007/978-981-13-7603-0_8
Finite element based dynamic analysis of multilayer fibre composite sandwich plates with interlayer delaminations
Jayatilake, Indunil N., Karunasena, Warna and Lokuge, Weena. 2016. "Finite element based dynamic analysis of multilayer fibre composite sandwich plates with interlayer delaminations." Advances in Aircraft and Spacecraft Science. 3 (1), pp. 15-28. https://doi.org/10.12989/aas.2016.3.1.015
Dynamic analysis of multilayer GFRP sandwich slabs with interlayer delaminations
Jayatilake, Indunil N., Karunasena, Warna and Lokuge, Weena. 2014. "Dynamic analysis of multilayer GFRP sandwich slabs with interlayer delaminations." Sabu, John and Das, Raj (ed.) 8th Australasian Congress on Applied Mechanics (ACAM 8). Melbourne, Australia 24 - 28 Nov 2014 Australia.
Dynamic behaviour of fibre composite multilayer sandwich plates with delaminations
Jayatilake, Indunil, Karunasena, Warna and Lokuge, Weena. 2014. "Dynamic behaviour of fibre composite multilayer sandwich plates with delaminations." Smith, Scott T. (ed.) 23rd Australasian Conference on the Mechanics of Structures and Materials (ACMSM23). Byron Bay, Australia 09 - 12 Dec 2014 Lismore, Australia.
Effect of skin-core debonding on the dynamic behaviour of GFRP composite beams
Jayatilake, Indunil, Karunasena, Warna and Lokuge, Weena. 2013. "Effect of skin-core debonding on the dynamic behaviour of GFRP composite beams." Epaarachchi, Jayantha A., Lau, Alan Kin-tak and Leng, Jinsong (ed.) 4th International Conference on Smart Materials and Nanotechnology in Engineering (SMN 2013). Gold Coast, Australia 10 - 12 Jul 2013 United States. https://doi.org/10.1117/12.2026751
Influence of single and multiple skin-core debonding on free vibration characteristics of innovative GFRP sandwich panels
Jayatilake, Indunil, Karunasena, Warna and Lokuge, Weena. 2016. "Influence of single and multiple skin-core debonding on free vibration characteristics of innovative GFRP sandwich panels." International Journal of Mechanical, Aerospace, Industrial and Mechatronics Engineering. 9 (5), pp. 800-804.
Free vibration behaviour of fibre composite sandwich beams with debonds
Karunasena, W., Jayatilake, I. and Lokuge, W.. 2013. "Free vibration behaviour of fibre composite sandwich beams with debonds." Dissanayake, Ranjith and Jayasinghe, Thishan (ed.) 4th International Conference on Structural Engineering and Construction Management 2013 (ICSECM 2013). Kandy, Sri Lanka 13 - 15 Dec 2013 Peradeniya, Sri Lanka.
Dynamic behaviour of debonded GFRP composite beams
Jayatilake, Indunil, Karunasena, Warna and Lokuge, Weena. 2013. "Dynamic behaviour of debonded GFRP composite beams." Journal of Multifunctional Composites. 1 (2), pp. 113-122. https://doi.org/10.12783/issn.2168-4286/1.2/Jayatilake
Response of tall buildings with symmetric setbacks under blast loading
Jayatilake, I. N., Dias, W. P. S., Jayasinghe, M. T. R. and Thambiratnam, D. P.. 2010. "Response of tall buildings with symmetric setbacks under blast loading." Journal of the National Science Foundation of Sri Lanka. 38 (2), pp. 115-123. https://doi.org/10.4038/jnsfsr.v38i2.2043
Study of transport of contaminants in a pipe network using the model EPANET
Ratnayake, Niranjanie and Jayatilake, Indunil N.. 1999. "Study of transport of contaminants in a pipe network using the model EPANET." 1st International Specialised Conference on Water Quality and Its Management (1998). India 02 - 06 Mar 1998 United Kingdom. https://doi.org/10.1016/S0273-1223(99)00473-4