An investigation of fatigue failure and damage development in carbon fibre epoxy resin composites
- Authors: Hluyo, Munyaradzi
- Date: 2016
- Subjects: Carbon fibers , Composite materials - Testing , Carbon fiber-reinforced plastics , Strength of materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/225092 , uj:22725
- Description: Abstract: The use of composite materials continuously extends design capabilities in all branches of engineering. Composite materials offer flexibility in design due to the fact that they can be manufactured to a wide set of custom requirements. For this reason, composite materials enable better application of their virtues while minimising deficiencies. Applications of Carbon Fibre Reinforced Composites (CFRCs) has been on the rise, with research focused on the advantages of CFRCs over conventional engineering materials. CFRCs are suitable for light weight applications and have a high resistance to fracture. These characteristics make them suitable for structural applications in automobiles, satellites and in the aerospace industry. CFRCs have a reputation for good fatigue behaviour and because of this, fatigue phenomenon is often ignored in composite material design, yet it is still an important problem from an engineering design perspective. This document presents an investigation on the performance of CFRCs exposed to cyclic loading. A thorough literature review on fatigue of CFRCs is presented. The different factors that affect fatigue of composite materials are discussed, including the damage mechanics, life prediction and a review of testing standards. Biaxial CFRC with a stacking sequence of [±45°]7 was used to make a composite of 30% fibre volume fraction in an Ampreg 21 epoxy resin. The composite specimens were manufactured using a hand layup moulding technique which was found to be the optimum process. A CNC cutting process was used for machining static and fatigue specimens. Static tests were conducted on the epoxy resin and CFRC to get the mechanical properties and to also determine the load levels to be used in the fatigue testing. Specimens were tested under a flexural fatigue load at three load levels which were selected as 25%, 50% and 75% of the proportionality limit. Damage development was monitored by the use of Electrical Strain Gages (ESGs). A post-test analysis was conducted by the use of an optical microscope, to clearly visualise the damage developed. The obtained results show that insignificant damage is observed at 25% load level with matrix cracking as the only damage mode, whilst mixed damage is observed at 50% and 75% load levels. , M.Ing. (Mechanical Engineering)
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- Authors: Hluyo, Munyaradzi
- Date: 2016
- Subjects: Carbon fibers , Composite materials - Testing , Carbon fiber-reinforced plastics , Strength of materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/225092 , uj:22725
- Description: Abstract: The use of composite materials continuously extends design capabilities in all branches of engineering. Composite materials offer flexibility in design due to the fact that they can be manufactured to a wide set of custom requirements. For this reason, composite materials enable better application of their virtues while minimising deficiencies. Applications of Carbon Fibre Reinforced Composites (CFRCs) has been on the rise, with research focused on the advantages of CFRCs over conventional engineering materials. CFRCs are suitable for light weight applications and have a high resistance to fracture. These characteristics make them suitable for structural applications in automobiles, satellites and in the aerospace industry. CFRCs have a reputation for good fatigue behaviour and because of this, fatigue phenomenon is often ignored in composite material design, yet it is still an important problem from an engineering design perspective. This document presents an investigation on the performance of CFRCs exposed to cyclic loading. A thorough literature review on fatigue of CFRCs is presented. The different factors that affect fatigue of composite materials are discussed, including the damage mechanics, life prediction and a review of testing standards. Biaxial CFRC with a stacking sequence of [±45°]7 was used to make a composite of 30% fibre volume fraction in an Ampreg 21 epoxy resin. The composite specimens were manufactured using a hand layup moulding technique which was found to be the optimum process. A CNC cutting process was used for machining static and fatigue specimens. Static tests were conducted on the epoxy resin and CFRC to get the mechanical properties and to also determine the load levels to be used in the fatigue testing. Specimens were tested under a flexural fatigue load at three load levels which were selected as 25%, 50% and 75% of the proportionality limit. Damage development was monitored by the use of Electrical Strain Gages (ESGs). A post-test analysis was conducted by the use of an optical microscope, to clearly visualise the damage developed. The obtained results show that insignificant damage is observed at 25% load level with matrix cracking as the only damage mode, whilst mixed damage is observed at 50% and 75% load levels. , M.Ing. (Mechanical Engineering)
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Experimental and numerical analysis of load transfer over a steel composite bonded joint
- Hluyo, Munyaradzi, Madyira, Daniel M., Janse van Rensburg, Nickey, Hurter, Warren
- Authors: Hluyo, Munyaradzi , Madyira, Daniel M. , Janse van Rensburg, Nickey , Hurter, Warren
- Date: 2016
- Subjects: Carbon fibre composites , Adhesive bonded joint , Load transfer
- Language: English
- Type: Conference proceeding
- Identifier: http://hdl.handle.net/10210/92090 , uj:20185 , Citation: Hluyo, M. et al. 2016. Experimental and numerical analysis of load transfer over a steel composite bonded joint.
- Description: Abstract: The current quest for low weight structures has led to a significant increase in the use of adhesive bonded joints more so for applications involving fibre reinforced composite materials. Adhesive bonded joints have major advantages over conventional joining methods such as riveting and bolting; and the nature of composite materials precludes use of other conventional methods such as welding, brazing and soldering. These advantages include lower structural weight due to lower density of the adhesive compared to traditional structural joining materials, lower fabrication costs, resistance to environmental degradation, better aesthetic appeal, lower stress concentrations, noise and vibration isolation capabilities and relative ease of use. Incorporating adhesive bonded joints into mechanical component design requires a higher level of understanding of adhesive joint behaviour. In particular it is important to understand the load transfer and joint failure mechanisms operative in the adhesive bonded joints. A lot of design information is available on conventional joining methods while information on design of bonded joints remains restricted to specialised applications such as automotive and aerospace . The aim of this paper is to investigate the effect of bond thickness on the load transfer between a steel insert and tubular glass fibre reinforced composite component under axial loading. A finite element analysis model is developed to analyse the behaviour of the joint . The model is validated using experimentally measured tensile response data for a selected insert length and adhesive layer thickness . The obtained results show the close relationship between the load transfer distances with adhesive elastic modulus. Furthermore the stress distribution along the adhesive bond layer was found to be independent of adhesive layer thickness. Adhesive layer thickness also has insignificant contribution to stress levels and load transfer distance.
- Full Text: false
- Authors: Hluyo, Munyaradzi , Madyira, Daniel M. , Janse van Rensburg, Nickey , Hurter, Warren
- Date: 2016
- Subjects: Carbon fibre composites , Adhesive bonded joint , Load transfer
- Language: English
- Type: Conference proceeding
- Identifier: http://hdl.handle.net/10210/92090 , uj:20185 , Citation: Hluyo, M. et al. 2016. Experimental and numerical analysis of load transfer over a steel composite bonded joint.
- Description: Abstract: The current quest for low weight structures has led to a significant increase in the use of adhesive bonded joints more so for applications involving fibre reinforced composite materials. Adhesive bonded joints have major advantages over conventional joining methods such as riveting and bolting; and the nature of composite materials precludes use of other conventional methods such as welding, brazing and soldering. These advantages include lower structural weight due to lower density of the adhesive compared to traditional structural joining materials, lower fabrication costs, resistance to environmental degradation, better aesthetic appeal, lower stress concentrations, noise and vibration isolation capabilities and relative ease of use. Incorporating adhesive bonded joints into mechanical component design requires a higher level of understanding of adhesive joint behaviour. In particular it is important to understand the load transfer and joint failure mechanisms operative in the adhesive bonded joints. A lot of design information is available on conventional joining methods while information on design of bonded joints remains restricted to specialised applications such as automotive and aerospace . The aim of this paper is to investigate the effect of bond thickness on the load transfer between a steel insert and tubular glass fibre reinforced composite component under axial loading. A finite element analysis model is developed to analyse the behaviour of the joint . The model is validated using experimentally measured tensile response data for a selected insert length and adhesive layer thickness . The obtained results show the close relationship between the load transfer distances with adhesive elastic modulus. Furthermore the stress distribution along the adhesive bond layer was found to be independent of adhesive layer thickness. Adhesive layer thickness also has insignificant contribution to stress levels and load transfer distance.
- Full Text: false
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