The Study Of Properties On Modified Epoxy And CFRP By MW-CNTs/CTBN

Carbon Fiber Reinforced Plastic(CFRP)are composites materials,which offer remarkable in-plane mechanical properties combined with low density.This unique property,make them being widely used for structural components especially in the aerospace industry.It offer strong structural integrity while maintaining its lightweightiness.Unlike metals,composites has anisotropic properties,meaning the behavior of FRP on different direction offer different result depending on the fiber reinforcement.Generally FRP are strong on x and y plane.The absence of z plane reinforcement,contribute to the lack z direction loading resistance like impact.This make FRP composites highly susceptible to impact damage in the form of matrix cracking and delamination.Delamination can occur inside the lamina,which severely reduce the performance of these composites,especially compressive strength.FRP composites is also exceptionally brittle due to the properties of thermoset materials(i.e.epoxy resin)used for matrix.The brittle nature of matrix does not allow the FRP to dissipate impact energy.It is believed,improving the toughness of the matrix able to improve the ability of the FRP to absorb impact energy from low-energy impact.Modifying the matrix to improve the toughness is believed to be the solution.Adding rubber to modify epoxy is one way to improve the toughness,the fundamental of this rubber modified epoxy has been well established.Incorporating small amount of rubber would in turn improve the toughness of epoxy considerably;however,it is followed by the decreased on other mechanical properties.Modifying epoxy with Carbon Nanotubes(CNTs)has been focus research for many scientist in recent years,CNTs offer high specific strength and stiffness,and is believed to be able to improve the toughness without decreasing the overall property of the epoxy.However,manufacturing well dispersed CNTs nanocomposite is a challenge.In this thesis,several different modified epoxy were studied.Carboxyl Terminated Butadiene Acrylonitrile(CTBN)rubber were used for rubber modified epoxy and Multi-walled Carbon Nanotubes(MW-CNTs)were used for CNTs modified epoxy.Several different content of CTBN and MW-CNTs were studied to determine the optimum combination to achieve binary modified epoxy.The present work investigates the effect of individual reinforcement on the property of epoxy;as well investigate the effect of binary reinforcement on the property of epoxy.After an introduction on available literature concerning the characteristics of each reinforcement,the procedure of sample preparation is presented.Samples were manufactured differently depending on the type of reinforcement,both modified epoxy were produced with compression molding.Three different content of CTBN were studied 5%;10%;and 15 wt.%,three different content of MW-CNTs were studied 0.3 wt.%;0.5 wt.%;and 1 wt.%.An effort was made to select the optimized parameters for binary modified epoxy.Several different characterization were performed in order to understand the behavior of modified epoxy,tensile testing,three-point bending,and Scanning Electron Microscope(SEM).In the evaluation of mechanical properties,tensile strength,toughness,strain to failure,flexural modulus,and flexural strength were obtained from tensile and three-point bending test.The fractured surface of modified epoxy were investigated by SEM surface imaging.On the evaluation of CTBN modified epoxy,the effect of different CTBN content on the property of epoxy is investigated.Modified epoxy with 5%;10%;15 wt.% of CTBN has been produced successfully.Incorporation of CTBN on epoxy resin proved to be able to increase the toughness of epoxy resin,however toughening phenomena can only be observed on modified epoxy with low CTBN content.The toughness of modified epoxy is observed to increases quite significant with 133% increases.Higher content of CTBN exhibit a decrease on the toughness.SEM observation on the fractured surface indicate that the main mechanism of toughening comes from second phase rubber formed on the epoxy matrix.Larger second rubber phase is observable on the epoxy with higher CTBN content(10% and 15 wt.%).This larger second rubber phase is observed to be ineffective on absorbing the energy,hence lower toughness is observed.A slight increase on tensile strength is observable on 5 wt.% CTBN,while flexural modulus and strength has decreases.Strain to failure has increases on CTBN modified epoxy,indicating a more ductile material is obtained.The observation of MW-CNTs modified epoxy,the effect of different MW-CNTs content on the property of epoxy is investigated.Modified epoxy with 0.3%;0.5%;1 wt.% of MW-CNTs has been produced successfully.The improvement on tensile strength is observed on 0.3 wt.% of MW-CNTs,increasing the MW-CNTs content are followed by declining tensile strength.SEM observation on the fractured surface of modified epoxy reveals the presence of MW-CNTs agglomerate on the epoxy matrix.Because of its small diameter while having long diameter,CNTs tend to bundle together forming agglomerate.This agglomeration is believed to act as stress concentrators,in which it can lower the performance of epoxy.Increasing the MW-CNTs content resulted on larger agglomerates formed.This contribute to the lower mechanical performance on those modified epoxy with higher MW-CNTs content.Toughness of MW-CNTs modified epoxy is observed to be improving as well;the most significant improvement is achieved by 0.3 wt.% of MWCNTs with 88%.Binary modified epoxy has been produced with specific CTBN and MW-CNTs.5 wt.% of CTBN and 0.3 wt.% of MW-CNTs are the obtained parameters from last observation on this study.The toughness of binary epoxy is observed has increased compared to neat epoxy,however is lower compared to those CTBN modified epoxy and MW-CNTs modified epoxy.Binary modified epoxy does not show significant improvement on the overall mechanical performance.SEM observation indicate that the agglomeration of MW-CNTs are the main reason for this result.Agglomerates on binary modified epoxy are larger compared to those of MW-CNTs modified epoxy,indicate that the dispersion of MW-CNTs are worse.It is believed that,incorporating both MW-CNTs and CTBN together would increase the viscosity of the mixture,which in turn would worsen the dispersion.To achieve a good dispersion of MW-CNTs on the binary modified epoxy,1 wt.% of solvent was added;moreover,ultra-sonication time was increased to 2 hours.Observation on the well-dispersed binary modified epoxy reveals that dispersion of MWCNTs has significant effect on the overall mechanical performance of binary modified epoxy.Toughness has increases considerably with 290% increase compared to neat epoxy.The other mechanical property is observed to improve as well.The use of binary modified epoxy to produce Carbon Fiber reinforced Plastic(CFRP)has been studied.Woven T300 carbon fiber fabric was used,the compression-molding combine with hand lay-up were used to manufacture the CFRP.Tensile and three-point bending were used to evaluate the mechanical performance of CFRP with modified epoxy.It is observed that CFRP with modified epoxy exhibit lower performance compared to those of CFRP without modified epoxy.Observation using SEM micrograph shows that the adhesion between carbon fiber and the matrix are weak,hence weak load transfer between fiber and the matrix,which resulted,on lower mechanical performance.Higher viscosity on modified epoxy mixture contribute to weak adhesion between carbon fiber and matrix.To observe the ability of modified epoxy to absorb impact energy,low-energy impact test was performed.The test was performed on three different energy level(5J;7.5J;10J).The extent of damage,type of damage is investigated by optical microscopy.The extent of damage can be observe with the indentation depth.It was reveal that CFRP with modified epoxy performed better on 5J and 7.5J impact energy with shallower damage observed compared to those of neat ones.Cracking,delamination,fiber breakage can be observed on both CFRP at high impact energy(10J).Compression after impact behavior reveal that CFRP with modified epoxy performed better by 15-19% at specific energy level.