Morphing leading edge has great potential for noise abatement and aerodynamic efficiency improvement.The drooping effect is realized by bending of the flexible skin which encloses to form the leading edge.Since the fl...Morphing leading edge has great potential for noise abatement and aerodynamic efficiency improvement.The drooping effect is realized by bending of the flexible skin which encloses to form the leading edge.Since the flexible skin is often made of composite laminates of Glass Fiber Reinforced Plastics(GFRP),the lay-up sequences have become the determinant,which affects not only the morphing quality but also the manufacturing complexity.Two optimizing methods of layup sequences are comparatively studied.In the first method,the laminal quantities in 0,±45and 90vary independently,while in the second one,the concept of isotropic laminate unit[0/45/45/90]s is employed and the unit quantity is the unique variable.Final evaluation demonstrates that for both methods there is insignificant impact to the overall morphing quality;however,specific concern is equally necessary for these two methods to the tip of the leading edge where the skin is at its minimum thickness and bears the most severe bending deformation.In terms of computational efficiency and post-processing labor,the second method has better performance.展开更多
As carbon fiber reinforced polymer （CFRP） material has been developed and demonstrated as an effective material in lightweight telescope reflector manufacturing recently, the authors of this article have extended to...As carbon fiber reinforced polymer （CFRP） material has been developed and demonstrated as an effective material in lightweight telescope reflector manufacturing recently, the authors of this article have extended to apply this material on the lightweight space camera mirror design and fabrication. By CFRP composite laminate design and optimization using finite element method （FEM） analysis, a spherical mirror with φ316 mm diameter whose core cell reinforcement is an isogrid configuration is fabricated. Compared with traditional ways of applying ultra-low-expansion glass （ULE） on the CFRP mirror surface, the method of nickel electroplating on the surface effectively reduces the processing cost and difficulty of the CFRP mirror. Through the FEM analysis, the first order resonance frequency of the CFRP mirror components reaches up to 652.3Hz. Under gravity affection coupling with ＋5℃ temperature rising, the mirror surface shape root-mean-square values （RMS） at the optical axis horizontal state is 5.74 nm, which meets mechanical and optical requirements of the mirror components on space camera.展开更多
From 1980’s decade,the introduction of carbon composite materials in structural applications has been consistently increased in the successive generations of civil aircraft from Single Aisle to Middle-long Range to a...From 1980’s decade,the introduction of carbon composite materials in structural applications has been consistently increased in the successive generations of civil aircraft from Single Aisle to Middle-long Range to achieve a culminant point with more than 50%in structure weight in recent commercial civil aircraft.This evolution,done through successive iterations,has been possible by combining in the same time the improvement of intrinsic composite material performances and its transformation into prepreg production technologies together with the development of new manufacturing process for material lay-up automation at composite shop-floor manufacturer of aircraft composite parts.New challenges are still coming to continuously develop materials and technologies in order to pursue the production more cost-effective composite parts.Associated to higher aircraft production rate for single aisle,new challenges may force material and aircraft designers and producers to furthermore drive new products and processes introduction and new ways of transformation within in next decade of composite aircraft designs.We propose to illustrate these trends using past and recent developments and our return of experience from Hexcel on Civil Aircraft programs.展开更多
To overcome warping in thin bamboo bundle veneer laminated composites(TBLC),their hydrothermal deformation characteristics were systematically investigated in this study.It was found that TBLCs accelerated the release...To overcome warping in thin bamboo bundle veneer laminated composites(TBLC),their hydrothermal deformation characteristics were systematically investigated in this study.It was found that TBLCs accelerated the release of internal stress in the thickness direction in a hydrothermal environment,which increased their warpage.TBLCs showed increased warpage in the width and diagonal directions upon increasing the temperature.The warpage of Type E increased by 155.88%and 66.67%in the width and diagonal directions,respectively,when the temperature increased from 25C to 100C.The symmetrical TBLC with cross-lay-up and odd layers displayed better hydrothermal stability.We revealed that the deformation of the TBLCs could be regulated under the synergistic effect of water and temperature.These results provide a scientific basis for improving the uniformity of bamboo bundle composite materials and for developing thin bamboo bundle fiber composite materials with designable structures and controllable performance.展开更多
This work addresses the tensile properties of glass fiber reinforced polymers (GFRP) and investigates the different ways of estimating them without the cost associated with experimentation. This attempt is achieved th...This work addresses the tensile properties of glass fiber reinforced polymers (GFRP) and investigates the different ways of estimating them without the cost associated with experimentation. This attempt is achieved through comparison between experimental results, derived in accordance with the ASTM standards, and results obtained using the mechanics of composite materials. The experimental results are also compared to results derived from work by other researchers in order to corroborate the findings regarding the correlation of tensile properties of the GFRP material and the fiber volume fraction.展开更多
Glass Fiber Reinforced Polymeric (GFRP)</span><span style="font-family:""> </span><span style="font-family:Verdana;">Composites are most commonly used as bumpers for ve...Glass Fiber Reinforced Polymeric (GFRP)</span><span style="font-family:""> </span><span style="font-family:Verdana;">Composites are most commonly used as bumpers for vehicles, electrical equipment panels, and medical devices enclosures. These materials are also widely used for structural applications in aerospace, automotive, and in providing alternatives to traditional metallic materials. The paper fabricated epoxy and polyester resin composites by using silicon carbide in various proportions along with GFRP. The hand lay-up technique was used to fabricate the laminates. To determine the properties of fabricated composites, </span><span style="font-family:Verdana;">the </span><span style="font-family:""><span style="font-family:Verdana;">tensile, impact, and flexural tests were conducted. This method of fabrication was very simple and cost-effective. Their mechan</span><span style="font-family:Verdana;">ical properties like yield strength, yield strain, Young’s modulus, flexural</span><span style="font-family:Verdana;"> mod</span><span style="font-family:Verdana;">ulus, and impact energy </span></span><span style="font-family:Verdana;">were</span><span style="font-family:Verdana;"> investigated. The mechanical properties of the</span><span style="font-family:""><span style="font-family:Verdana;"> GFRP composites were also compared with the fiber volume fraction. The fiber volume fraction plays a major role in the mechanical properties of GFRP composites. Young’s modulus and tensile strength of fabricated composites </span><span style="font-family:Verdana;">were modelled and compared with measured values. The results show that</span><span style="font-family:Verdana;"> composites </span><span style="font-family:Verdana;">with epoxy resin demonstrate higher strength and modulus compared to</span><span style="font-family:Verdana;"> composites with polyester resin.展开更多
The mechanical properties of raffia palm fibre and groundnut shell particulate/epoxy (RPF/GSP/E) hybrid composites have been studied. Raffia palm fibres were treated with 10% NaOH solution at room temperature, and gro...The mechanical properties of raffia palm fibre and groundnut shell particulate/epoxy (RPF/GSP/E) hybrid composites have been studied. Raffia palm fibres were treated with 10% NaOH solution at room temperature, and groundnut shell particulate of different sizes;75 μ, 150 μ and 300 μ were also chemically treated with 10% NaOH solution at room temperature. The hybrid composite was produced by hand lay-up technique with (10%, 20%, 30%, 40%, and 50%) reinforcements of raffia palm fibre and ground nut shell particulate in the ratio of 1:1. The treated fibres were taken with required weight fractions laid into the mould of size 200 × 150 × 5 mm3. Groundnut shell particulates were also taken with the required weight fraction, mixed with epoxy resin and the mixture was stirred thoroughly before pouring into the mould. Care was taken to avoid formation of air bubbles during pouring and the produced composite was cured under a load of 25 kg for 24 hours before it was removed from the mould. Effects of loading on the tensile, flexural and impact properties of the composite were evaluated. The significant findings of the results were that: tensile strength varied from 1.88 MPa to 9.56 MPa;Modulus of rupture (MOR) varied from 1.92 MPa to 41.6 MPa. While the modulus of elasticity, (MOE) values were in the range of 131.1 MPa to 4720 MPa and impact strength varied from 0.3 kJ/m2 to 1.6 kJ/m2. From the results obtained, the optimum mechanical properties were obtained at 40% loading of RPF/300 μ GSP/E composite. Considering these results, the composite material can be considered as an alternative material for use in automotive interior panels such as boot liner, side and door panels, rear storage shelf and roof cover.展开更多
Mechanical properties of ukam, banana, sisal, coconut, hemp and e-glass fibre reinforced laminates were evaluated to assess the possibility of using it as new material in engineering applications. Samples were fabrica...Mechanical properties of ukam, banana, sisal, coconut, hemp and e-glass fibre reinforced laminates were evaluated to assess the possibility of using it as new material in engineering applications. Samples were fabricated by the hand lay-up process (30:70 fibre and matrix ratio by weight) and the properties evaluated using the INSTRON material testing system. The mechanical properties were tested and showed that glass laminate has the maximum tensile strength of 63 MPa, bending strength of 0.5 MPa, compressive strength of 37.75 MPa and the impact strength of 17.82 J/m2. The ukam plant fibre laminate has the maximum tensile strength of 16.25 MPa and the impact strength of 9.8J/m among the natural fibres;the sisal laminate has the maximum compressive strength of 42 MPa and maximum bending strength of 0.0036 MPa among the natural fibres. Results indicated that natural fibres are of interest for low-cost engineering applications and can compete with artificial glass fibres (E-glass fibre) when a high stiffness per unit weight is desirable. Results also indicated that future research towards significant improvements in tensile and impact strength of these types of composites should focus on the optimisation of fibre strength rather than interfacial bond strength.展开更多
Effects of the processing methods on the mechanical properties of treated bagasse fibre reinforced epoxy composite were evaluated. The composite materials were processed by employing hand lay-up and compression mouldi...Effects of the processing methods on the mechanical properties of treated bagasse fibre reinforced epoxy composite were evaluated. The composite materials were processed by employing hand lay-up and compression moulding methods and fibres were treated with NaOH solution. The composite samples were subjected to tensile, flexural and impact tests. Based on the findings, compression moulding method produced better mechanical properties compared to the composites manufactured by hand lay-up method. The results showed that the tensile strength and Young’s modulus of the samples produced by compression moulding method increased by 77 percent and 47 percent respectively (at optimal fibre loading) compared to those produced by the hand lay-up method. The results also showed noticeable improvements in the impact strength of the material produced by compression moulding method, with impact strength of 11.5 kJ/m2 against the samples produced by hand lay-up method, with impact strength of 7 kJ/m2.展开更多
Effects of layer quantities and stacking sequences on L-shape composite manufacturing qualities in using OOA(out-of-autoclave)prepregs were studied.The mechanisms of air evacuated in 5 kinds of lay-ups were revealed b...Effects of layer quantities and stacking sequences on L-shape composite manufacturing qualities in using OOA(out-of-autoclave)prepregs were studied.The mechanisms of air evacuated in 5 kinds of lay-ups were revealed by image analysis of cut surfaces and thickness measurements.Results show that air in OOA prepregs is evacuated in two ways.Most of the air is forced out of layers directly by vacuum before air accesses in prepregs closed.Very little entrapped air moves perpendicularly to outer layers under hydrostatic resin pressure.When a laminate contains less than 16 layers,voids can hardly be found in layers.When a laminate contains more than 16 layers,voids cannot be expelled completely during the window of vertical movement.As for stacking sequences,the synergetic effect of slip function and nest function determines the thickness and voids content of laminates.Results show that the average of single layer thickness of unidirectional layers is the lowest,and the average of single layer thickness of quasi-isotropic layers is the highest.The voids content of quasi isotropic is the highest,which is consistent with the theoretical analysis.展开更多
文摘Morphing leading edge has great potential for noise abatement and aerodynamic efficiency improvement.The drooping effect is realized by bending of the flexible skin which encloses to form the leading edge.Since the flexible skin is often made of composite laminates of Glass Fiber Reinforced Plastics(GFRP),the lay-up sequences have become the determinant,which affects not only the morphing quality but also the manufacturing complexity.Two optimizing methods of layup sequences are comparatively studied.In the first method,the laminal quantities in 0,±45and 90vary independently,while in the second one,the concept of isotropic laminate unit[0/45/45/90]s is employed and the unit quantity is the unique variable.Final evaluation demonstrates that for both methods there is insignificant impact to the overall morphing quality;however,specific concern is equally necessary for these two methods to the tip of the leading edge where the skin is at its minimum thickness and bears the most severe bending deformation.In terms of computational efficiency and post-processing labor,the second method has better performance.
基金Acknowledgement This work was supported by the National Natural Science Foundation of China （NSFC） （No. 41501383）.
文摘As carbon fiber reinforced polymer （CFRP） material has been developed and demonstrated as an effective material in lightweight telescope reflector manufacturing recently, the authors of this article have extended to apply this material on the lightweight space camera mirror design and fabrication. By CFRP composite laminate design and optimization using finite element method （FEM） analysis, a spherical mirror with φ316 mm diameter whose core cell reinforcement is an isogrid configuration is fabricated. Compared with traditional ways of applying ultra-low-expansion glass （ULE） on the CFRP mirror surface, the method of nickel electroplating on the surface effectively reduces the processing cost and difficulty of the CFRP mirror. Through the FEM analysis, the first order resonance frequency of the CFRP mirror components reaches up to 652.3Hz. Under gravity affection coupling with ＋5℃ temperature rising, the mirror surface shape root-mean-square values （RMS） at the optical axis horizontal state is 5.74 nm, which meets mechanical and optical requirements of the mirror components on space camera.
文摘From 1980’s decade,the introduction of carbon composite materials in structural applications has been consistently increased in the successive generations of civil aircraft from Single Aisle to Middle-long Range to achieve a culminant point with more than 50%in structure weight in recent commercial civil aircraft.This evolution,done through successive iterations,has been possible by combining in the same time the improvement of intrinsic composite material performances and its transformation into prepreg production technologies together with the development of new manufacturing process for material lay-up automation at composite shop-floor manufacturer of aircraft composite parts.New challenges are still coming to continuously develop materials and technologies in order to pursue the production more cost-effective composite parts.Associated to higher aircraft production rate for single aisle,new challenges may force material and aircraft designers and producers to furthermore drive new products and processes introduction and new ways of transformation within in next decade of composite aircraft designs.We propose to illustrate these trends using past and recent developments and our return of experience from Hexcel on Civil Aircraft programs.
基金supported by the Youth Top-notch Talent Program of Science and Technology Innovation for Forestry and Grassland(2019132606).
文摘To overcome warping in thin bamboo bundle veneer laminated composites(TBLC),their hydrothermal deformation characteristics were systematically investigated in this study.It was found that TBLCs accelerated the release of internal stress in the thickness direction in a hydrothermal environment,which increased their warpage.TBLCs showed increased warpage in the width and diagonal directions upon increasing the temperature.The warpage of Type E increased by 155.88%and 66.67%in the width and diagonal directions,respectively,when the temperature increased from 25C to 100C.The symmetrical TBLC with cross-lay-up and odd layers displayed better hydrothermal stability.We revealed that the deformation of the TBLCs could be regulated under the synergistic effect of water and temperature.These results provide a scientific basis for improving the uniformity of bamboo bundle composite materials and for developing thin bamboo bundle fiber composite materials with designable structures and controllable performance.
文摘This work addresses the tensile properties of glass fiber reinforced polymers (GFRP) and investigates the different ways of estimating them without the cost associated with experimentation. This attempt is achieved through comparison between experimental results, derived in accordance with the ASTM standards, and results obtained using the mechanics of composite materials. The experimental results are also compared to results derived from work by other researchers in order to corroborate the findings regarding the correlation of tensile properties of the GFRP material and the fiber volume fraction.
文摘Glass Fiber Reinforced Polymeric (GFRP)</span><span style="font-family:""> </span><span style="font-family:Verdana;">Composites are most commonly used as bumpers for vehicles, electrical equipment panels, and medical devices enclosures. These materials are also widely used for structural applications in aerospace, automotive, and in providing alternatives to traditional metallic materials. The paper fabricated epoxy and polyester resin composites by using silicon carbide in various proportions along with GFRP. The hand lay-up technique was used to fabricate the laminates. To determine the properties of fabricated composites, </span><span style="font-family:Verdana;">the </span><span style="font-family:""><span style="font-family:Verdana;">tensile, impact, and flexural tests were conducted. This method of fabrication was very simple and cost-effective. Their mechan</span><span style="font-family:Verdana;">ical properties like yield strength, yield strain, Young’s modulus, flexural</span><span style="font-family:Verdana;"> mod</span><span style="font-family:Verdana;">ulus, and impact energy </span></span><span style="font-family:Verdana;">were</span><span style="font-family:Verdana;"> investigated. The mechanical properties of the</span><span style="font-family:""><span style="font-family:Verdana;"> GFRP composites were also compared with the fiber volume fraction. The fiber volume fraction plays a major role in the mechanical properties of GFRP composites. Young’s modulus and tensile strength of fabricated composites </span><span style="font-family:Verdana;">were modelled and compared with measured values. The results show that</span><span style="font-family:Verdana;"> composites </span><span style="font-family:Verdana;">with epoxy resin demonstrate higher strength and modulus compared to</span><span style="font-family:Verdana;"> composites with polyester resin.
文摘The mechanical properties of raffia palm fibre and groundnut shell particulate/epoxy (RPF/GSP/E) hybrid composites have been studied. Raffia palm fibres were treated with 10% NaOH solution at room temperature, and groundnut shell particulate of different sizes;75 μ, 150 μ and 300 μ were also chemically treated with 10% NaOH solution at room temperature. The hybrid composite was produced by hand lay-up technique with (10%, 20%, 30%, 40%, and 50%) reinforcements of raffia palm fibre and ground nut shell particulate in the ratio of 1:1. The treated fibres were taken with required weight fractions laid into the mould of size 200 × 150 × 5 mm3. Groundnut shell particulates were also taken with the required weight fraction, mixed with epoxy resin and the mixture was stirred thoroughly before pouring into the mould. Care was taken to avoid formation of air bubbles during pouring and the produced composite was cured under a load of 25 kg for 24 hours before it was removed from the mould. Effects of loading on the tensile, flexural and impact properties of the composite were evaluated. The significant findings of the results were that: tensile strength varied from 1.88 MPa to 9.56 MPa;Modulus of rupture (MOR) varied from 1.92 MPa to 41.6 MPa. While the modulus of elasticity, (MOE) values were in the range of 131.1 MPa to 4720 MPa and impact strength varied from 0.3 kJ/m2 to 1.6 kJ/m2. From the results obtained, the optimum mechanical properties were obtained at 40% loading of RPF/300 μ GSP/E composite. Considering these results, the composite material can be considered as an alternative material for use in automotive interior panels such as boot liner, side and door panels, rear storage shelf and roof cover.
文摘Mechanical properties of ukam, banana, sisal, coconut, hemp and e-glass fibre reinforced laminates were evaluated to assess the possibility of using it as new material in engineering applications. Samples were fabricated by the hand lay-up process (30:70 fibre and matrix ratio by weight) and the properties evaluated using the INSTRON material testing system. The mechanical properties were tested and showed that glass laminate has the maximum tensile strength of 63 MPa, bending strength of 0.5 MPa, compressive strength of 37.75 MPa and the impact strength of 17.82 J/m2. The ukam plant fibre laminate has the maximum tensile strength of 16.25 MPa and the impact strength of 9.8J/m among the natural fibres;the sisal laminate has the maximum compressive strength of 42 MPa and maximum bending strength of 0.0036 MPa among the natural fibres. Results indicated that natural fibres are of interest for low-cost engineering applications and can compete with artificial glass fibres (E-glass fibre) when a high stiffness per unit weight is desirable. Results also indicated that future research towards significant improvements in tensile and impact strength of these types of composites should focus on the optimisation of fibre strength rather than interfacial bond strength.
文摘Effects of the processing methods on the mechanical properties of treated bagasse fibre reinforced epoxy composite were evaluated. The composite materials were processed by employing hand lay-up and compression moulding methods and fibres were treated with NaOH solution. The composite samples were subjected to tensile, flexural and impact tests. Based on the findings, compression moulding method produced better mechanical properties compared to the composites manufactured by hand lay-up method. The results showed that the tensile strength and Young’s modulus of the samples produced by compression moulding method increased by 77 percent and 47 percent respectively (at optimal fibre loading) compared to those produced by the hand lay-up method. The results also showed noticeable improvements in the impact strength of the material produced by compression moulding method, with impact strength of 11.5 kJ/m2 against the samples produced by hand lay-up method, with impact strength of 7 kJ/m2.
文摘Effects of layer quantities and stacking sequences on L-shape composite manufacturing qualities in using OOA(out-of-autoclave)prepregs were studied.The mechanisms of air evacuated in 5 kinds of lay-ups were revealed by image analysis of cut surfaces and thickness measurements.Results show that air in OOA prepregs is evacuated in two ways.Most of the air is forced out of layers directly by vacuum before air accesses in prepregs closed.Very little entrapped air moves perpendicularly to outer layers under hydrostatic resin pressure.When a laminate contains less than 16 layers,voids can hardly be found in layers.When a laminate contains more than 16 layers,voids cannot be expelled completely during the window of vertical movement.As for stacking sequences,the synergetic effect of slip function and nest function determines the thickness and voids content of laminates.Results show that the average of single layer thickness of unidirectional layers is the lowest,and the average of single layer thickness of quasi-isotropic layers is the highest.The voids content of quasi isotropic is the highest,which is consistent with the theoretical analysis.
