Abstract:In this work, Epocast 50-A1/946 epoxy have been modified with different weight percentages (0.25, 0.5, 0.75, 0.1, 1.25, and 1.5 wt%) of multiwalled carbon nanotubes (MWCNTs). Because of Epocast epoxy was primarily developed for joining and repairing of composite aircraft structural components, the optimum weight percentage of MWCNTs must be determined based on trade-offs between the optimum tensile, inplane shear and toughness properties of the developed MWCNTs-composites, which is the objective of this study.… Show more
“…A sudden drop to zero-force was observed at the maximum contact force, demonstrating a brittle failure (fracture) of SAJs and provides a measurement of the displacement at maximum force. This behavior was attributed to the elastic-brittle behavior of either the bulk adhesive 3,40 or SAJs, [5][6][7] as shown in the tensile tests at RT. Moreover, the load-displacement curves of the CFRE laminates, in low-velocity impact tests, showed an elastic-brittle behavior at RT and 50 C. 33 Khashaba and Othman 33 have reported that the increasing of the test temperature from RT to 50 C has insignificant effects on the damage resistance of CFRE laminates under low-velocity impact loads.…”
Section: Load-displacement Curves Of Drop-weight Impact Testsmentioning
Scarf adhesive joints have attracted an increasing attention in joining/repairing of carbon fiber reinforced epoxy composite structures due to their zero eccentricity, which provides lower stress distribution across the adhesive layer and better aerodynamic surfaces compared to other bonded joints. The main objective of this study is to evaluate the performance of the scarf adhesive joints in carbon fiber reinforced epoxy composites under thermomechanical impact loads, which is very important for the aerospace and automotive industries. The adhesive was modified with optimum percentage of multiwalled carbon nanotubes. The impact tests were performed at 25 ℃, 50 ℃, and 75 ℃. The residual flexural properties of the unfailed impacted joints were measured using three-point bending test. Results from impact tests at 25 ℃, 50 ℃, and 75 ℃ showed improvement in the impact bending stiffness of the modified scarf adhesive joints by 8.3%, 7.4%, and 11.8% and maximum contact force by 15.6%, 21.3%, and 18.9%, respectively. The energy at failure of the modified scarf adhesive joints with multiwalled carbon nanotubes was improved by 15.2% and 16.4% respectively at 25 ℃ and 50 ℃. At test temperature of 75 ℃, the scarf adhesive joints have hysteresis load–displacement behavior and energy–time curve with rebound energy of 35% and absorbed (damage) energy of 65%. The residual flexural strength of the modified and unmodified scarf adhesive joints is 98.2% and 86.1% respectively, while their residual moduli have remarkable decrease to 71.7% and 81.3%.
“…A sudden drop to zero-force was observed at the maximum contact force, demonstrating a brittle failure (fracture) of SAJs and provides a measurement of the displacement at maximum force. This behavior was attributed to the elastic-brittle behavior of either the bulk adhesive 3,40 or SAJs, [5][6][7] as shown in the tensile tests at RT. Moreover, the load-displacement curves of the CFRE laminates, in low-velocity impact tests, showed an elastic-brittle behavior at RT and 50 C. 33 Khashaba and Othman 33 have reported that the increasing of the test temperature from RT to 50 C has insignificant effects on the damage resistance of CFRE laminates under low-velocity impact loads.…”
Section: Load-displacement Curves Of Drop-weight Impact Testsmentioning
Scarf adhesive joints have attracted an increasing attention in joining/repairing of carbon fiber reinforced epoxy composite structures due to their zero eccentricity, which provides lower stress distribution across the adhesive layer and better aerodynamic surfaces compared to other bonded joints. The main objective of this study is to evaluate the performance of the scarf adhesive joints in carbon fiber reinforced epoxy composites under thermomechanical impact loads, which is very important for the aerospace and automotive industries. The adhesive was modified with optimum percentage of multiwalled carbon nanotubes. The impact tests were performed at 25 ℃, 50 ℃, and 75 ℃. The residual flexural properties of the unfailed impacted joints were measured using three-point bending test. Results from impact tests at 25 ℃, 50 ℃, and 75 ℃ showed improvement in the impact bending stiffness of the modified scarf adhesive joints by 8.3%, 7.4%, and 11.8% and maximum contact force by 15.6%, 21.3%, and 18.9%, respectively. The energy at failure of the modified scarf adhesive joints with multiwalled carbon nanotubes was improved by 15.2% and 16.4% respectively at 25 ℃ and 50 ℃. At test temperature of 75 ℃, the scarf adhesive joints have hysteresis load–displacement behavior and energy–time curve with rebound energy of 35% and absorbed (damage) energy of 65%. The residual flexural strength of the modified and unmodified scarf adhesive joints is 98.2% and 86.1% respectively, while their residual moduli have remarkable decrease to 71.7% and 81.3%.
“…Hence, the specimen gauge region is under a state of constant shear force and pure shear stress (zero bending moment), which can be demonstrated by the shear-force and bending-moment diagrams of Iosipescu shear test specimen as illustrated elsewhere by Khashaba. 3,28 Figure 1.Experimental setup of the in-plane Iosipescu shear test.Figure 2.(a) Dimensions of the double V-notches specimen, ASTM D5379, and (b) the instrumented specimens.…”
The present work aims to improve the mechanical properties of Epocast 50-A1/946 epoxy via incorporation of alumina nanoparticles using an ultrasonic agitation method. The optimum weight percentage of alumina nanoparticles was determined based on the improvement in the shear and impact properties of the nanocomposites at room temperature and 50 ℃. Accordingly, neat epoxy panels and nanocomposite panels with 0.5, 1.0, 1.5, and 2.0 wt% alumina nanoparticles were fabricated. The shear and thermo-mechanical impact properties of the panels were measured using an instrumented drop-weight impact machine and an Iosipescu shear test fixture, respectively, according to ASTMs D5379 and D7136. The maximum improvement in shear strength and modulus was 10.9% and 8.1%, respectively, for the nanocomposites containing 1.0 and 1.5 wt% alumina nanoparticles. The predicted shear moduli of the nanocomposites agreed well with the measured values with a maximum error of 6.52%. The optimal performance of impact properties was achieved by incorporating 1.0 wt% of alumina nanoparticles. Namely, the maximum impact-bending stiffness, contact force, and absorbed energy were increased by 12.9%, 13.0%, and 23.4%, respectively. The test temperature of 50 ℃ was found to have a negative effect on the impact-bending stiffness and the maximum contact force. On the other hand, the absorbed energy was increased up to 12.1%.
“…Because MWCNTs have large aspect ratio (length/ diameter), they tend to aggregate and form bundles or ropes, usually with highly entangled network structure, which significantly limits their dispersion in the epoxy resin. Agglomerations of MWCNTs reduce the interfacial area in the nanocomposites, and hence reduce the opportunity to take the advantage of the unique properties of the MWCNTs [19] . Based on the extensive literature survey, a 0.5wt% MWCNTs was selected, which showed improvements in the mechanical properties for different epoxy systems by many researchers [2][3][4][5][6][7][8][9][10][11] .…”
Section: Determination the Mass Of Mwcnts And Epoxymentioning
In the present work, tensile, shear and impact properties of epoxy modified with multi-walled carbon nanotubes (MWCNTs) are measured experimentally in accordance with ASTM standards. The MWCNTs were dispersed into the epoxy resin using ultrasonic processor. To avoid damaging the nanotubes, the sonication process was performed at low-amplitude (225W) in a short duration of 30 min. The mixture was evacuated to remove air bubbles before further mixing with hardener. Results from the experimental study showed that incorporation of the MWCNTs into the epoxy resin improves the tensile strength and modulus of the MWCNT-nanocomposite by 11% and 68.7%, respectively, compared with those of the neat epoxy. The shear strength and inplane shear modulus of the MWCNT-nanocomposite were improved by 22.2% and 29%, respectively. The drop weight impact performance of the MWCNT-nanocomposite showed an improvement in the maximum contact force and the absorbed energy of the MWCNT-nanocomposite by 9.5% and 11.4%, respectively.
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