|Title:||Development of an ultraviolet-protective glass fibre reinforced epoxy composite|
|Advisors:||Lau, Kin-tak Alan (ME)|
Tam, Wai-yin (ME)
Hong Kong Polytechnic University -- Dissertations
|Department:||Department of Mechanical Engineering|
|Pages:||xxxiii, 247 pages : color illustrations|
|Abstract:||With the increasing utilization of fibre reinforced polymer-based composites (FRPs) in aircraft, civil construction and automobile engineering industries, longterm durability is critical to FRPs. In another word, it is essential to maintain the structural strength of FRPs under various environmental effects (such as UVR, temperature and moisture) with the change of time. FRPs are inevitably in contact with UVR from sunlight during service. Nowadays, at least 50% fuselage materials of commercial aircraft A350 and B787 are implemented with FRPs. The roofs and facades on buildings and deck panels on bridges made by FRPs are found everywhere. Ultraviolet radiation (UVR), an inherent stimulus to human body and polymer-based materials, poses negative effects to the health of exposed organisms and strength of exposed materials. To protect polymer-based materials from UVR degradation, inorganic zinc oxide (ZnO) particle is proposed to alleviate the chemical UVR absorption of polymers and simultaneously enhance the physical UVR absorption. ZnO is able to physically absorb UVR and gives full UVR spectrum absorption. Besides, it is relatively inexpensive and easy for processing. Moreover, nanoparticle dissolution out of polymers could happen when contacting with UVR and ionic solutions. Hollow glass fibre (HGF) is introduced to protect the nanoparticles from dissolution and simultaneously reinforce the polymer surface from wearing problem as hollow glass fibre generally has high wearability. As a result, ZnO/HGF is engineered to be the top lamina of glass fibre reinforced epoxy composite for the protection purpose.|
100nm ZnO particle is found in present research performing with optimized results in UVR absorption with good particle dispersion in epoxy, unsaturated polyester, epoxy-based and styrene-based shape memory polymers (EP-and S-SMPs). 4 wt.% 100nm ZnO particle mixed with epoxy is filled into HGF by using vacuum infiltration technique and exhibits uniform particle dispersion and good rheology properties. 4 wt.% 100nm ZnO/HGF lamina achieves high UVR absorption among the tested samples including epoxy, 2 wt.% and 7 wt.% 100nm ZnO/HGF laminas. Particle agglomeration occurs when the particle content is increased to 7 wt.% which its lamina results in having the lowest UVR absorption. 4 wt.% 100nm ZnO also exhibits good particle dispersion, UVR absorption and therefore is able to maintain the surface hardness and shape memory effects in EP-and S-SMPs after UVA exposure. The surface morphology and tensile properties of glass fibre unsaturated polyester composite with 6 wt.% 100nm ZnO implemented in the first three layers of glass fabric underwent accelerated continuous and cyclic UVA exposure are compared. Their surface morphology has no significant difference but their tensile properties are found otherwise. The rate of change of the Young's modulus of the composite underwent continuous UVA exposure is 2 times higher than that with cyclic UVA exposure. Similar result is found in the tensile strength which is 1.16 times higher. Mechanical properties should be the determinant for the degradation rate of composites and estimation on their service life. Theoretical model is developed for the parameter optimization in designing the configuration of ZnO/HGF lamina based on stress transfer ability. Together with the results obtained from experimental analysis, 4 wt.% 100nm ZnO/HGF lamina with longer length of HGF has good stress transfer ability, load carrying capability, particle dispersion and UVR resistibility. Up to the moment in present research, it has been revealed that there are plenty of potential in the investigation of the UVR degradation and resistance in polymer-based composites. More details will be addressed in the last chapter of this thesis, Chapter Nine Concluding Remarks and Suggestions for Future Development.
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