Thermo-Stamping Process of Glass and Carbon-Fibre Reinforced Polymer Composites

In this work, manufacturing tools for thermoplastic (TP) composites have been developed. The chosen process involves the stacking alternately of oriented dry fabrics and TP films and does not use semi-products in order to reduce material costs. This study was specifically directed towards optimizing the impregnation of continuous glass and carbon fibres reinforcing two TP amorphous matrices, the polyphenylsulfone (PPSU) and polyetherimide (PEI), to obtain semi-finished products employed for aeronautical structures. The impregnation quality of inter and intra-yarns is analyzed and validated by optical and scanning micrographic observations conducted with an optical and a Scanning Electron Microscopies (SEM), respectively. The study showed that besides the process parameters and porosity distribution in the core of warp yarns, the impregnation quality depends on the surface properties of constituents. Desizing treatment has been carried out to improve the wettability of fibres by the TP matrices.

Quasi-plane-hypothesis of strain coordination for RC beams seismically strengthened with externally-bonded or near-surface mounted fiber reinforced plastic

The application of fiber reinforced plastic（FRP）,including carbon FRP and glass FRP,for structural repair and strengthening has grown due to their numerous advantages over conventional materials such as externally bonded reinforcement（EBR） and near-surface mounted（NSM） strengthening techniques.This paper summarizes the results from 21 reinforced concrete beams strengthened with different methods,including externally-bonded and near-surface mounted FRP,to study the strain coordination of the FRP and steel rebar of the RC beam.Since there is relative slipping between the RC beam and the FRP,the strain of the FRP and steel rebar of the RC beam satisfy the quasi-plane-hypothesis;that is,the strain of the longitudinal fiber that parallels the neutral axis of the plated beam within the scope of the effective height（h 0） of the cross section is in direct proportion to the distance from the fiber to the neutral axis.The strain of the FRP and steel rebar satisfies the equation：ε FRP =βε steel,and the value of β is equal to 1.1-1.3 according to the test results.

Strain coordination of quasi-plane-hypothesis for reinforced concrete beam strengthened by epoxy-bonded glass fiber reinforced plastic plate

The testing of thirteen reinforeed concrete （RC） beams strengthened by epoxy-bonded glass fiber reinforced plastic plate （GFRP） shows that the RC beam and the GFRP plate with epoxy bonding on it can work fairly well in coordination to eaeh other. But there is relative slipping between RC beam and GFRP plate. And the strain of GFRP and steel rebar of RC beam satisfies the quasi-plane-hypothesis, that is, the strain of longitudinal fiher that parallels to the neutral axis of plated beam within the scope of effective height （ h0 ） of the cross section is in direct proportion to the distance from the fiber to the neutral axis. The strain of GFRP and steel rebar satisfies the equation： εGFRP=Kεsteel.

Development and Properties of Glass Fiber Reinforced Plastics Geogrid

Glass fiber reinforced plastics geogrid has a wide application in the field of soil reinforcement because of its high strength, good toughness, and resistance to environmental stress, creep resistance and strong stability. In order to get high-powered glass fiber reinforced plastics geogrid and its mechanical characteristics, the properties and physical mechanical index of geogrid have been got through the study of its raw material, production process and important quality index. The analysis and study have been made to the geogrid＇s mechanical properties with loading speed, three-axial compression, temperature tensile test and FLAC3D numerical simulation, thus obtain the mechanical parameters of its displacement time curve, breaking strength and elongation at break. Some conclusions can be drawn as follows： （a） Using glass fiber materials, knurling and coated projection process, the f^acture strength and corrosion resistance of geogrid are greatly improved and the interlocking bite capability of soil is enhanced. （b） The fracture strength of geogrid is related to temperature and loading rate. When the surrounding rock pressure is fixed, the strength and anti-deformation ability of reinforced soil are significantly enhanced with increasing reinforced layers. （c） The pullout test shows the positive correlation between geogrid displacement and action time. （d） As a new reinforced material, the glass fiber reinforced plastics geogrid is not mature enough in theoretical research and practical experience, so it has become an urgent problem both in theoretical study and practical innovation.

Entrance and Exit Defects During Coarse Pitch Orbital Drilling of Carbon Fiber Reinforced Plastic Plates

Formation of entrance and exit defects in coarse pitch orbital drilling(CPOD)of carbon fiber reinforced plastic(CFRP)plates was investigated.Deep observation on entrance and exit morphology shows tear and burr are typical defects.Meanwhile,tear is more obvious than burr,and more entrance tears emerge than exit tears.As one of the major causes of entrance and exit defects in CPOD,cutting forces were substaintially studied by contrast experiments.Then,the effect of cutting parameters on entrance and exit tear was qualitatively analyzed through a single factor test.Experiment results indicate that the variation of rotation speed has little influence on entrance and exit tear.Increasing tangential feed per tooth can enlarge entrance tear,but bring little effect on exit tear.By increasing axial feed pitch,the hole entrance and exit show severe tear.When revolution radius grows bigger and bigger,entrance and exit tear firstly decreases,and then increases.Finally,the models of tear and delamination during CPOD of CFRP were established,the formation mechanisms of entrance and exit defects were revealed,and the control strategies were accordingly put forward.

Double linear strain distribution assumption of RC beam strengthened with external-bonded or near-surface mounted fiber reinforced plastic

Rehabilitation of existing structures with fiber reinforced plastic(FRP)has been growing in popularity because they offer superior performance in terms of resistance to corrosion and high specific stiffness.The strain coordination results of 34 reinforced concrete beams(four groups)strengthened with different methods were presented including external-bonded or near-surface mounted glass or carbon FRP or helical rib bar in order to study the strain coordination of the strengthening materials and steel rebar of RC beam.Because there is relative slipping between concrete and strengthening materials(SM),the strain of SM and steel rebar of RC beam satisfies the double linear strain distribution assumption,that is,the strain of longitudinal fiber parallel to the neutral axis of plated beam within the scope of effective height(h0)of the cross section is in direct proportion to the distance from the fiber to the neutral axis.The strain of SM and steel rebar satisfies the equation εGCH=βεsteel,where the value of β is equal to 1.1-1.3 according to the test results.

Characterization of carbon fibers recovered through mechanochemical-enhanced recycling of waste carbon fiber reinforced plastics

In this study,we present the characterization of the carbon fibers recovered from the mechanochemical-enhanced recycling of carbon fiber reinforced fibers.The objectives of the study were to investigate the effect of our modified recycling method on the interfacial properties of recovered fibers.The reinforced plastics were recycled;the recycling efficiency was determined and the recovered fibers were sized using 1 wt%and 3 wt%concentration of(3-aminopropyl)triethoxysilane.We characterized the morphologies utilizing the electron spectroscopy for chemical analysis(ESCA),atomic force microscopy(AFM),FTIR-attenuated total reflection(ATR)spectroscopy and scanning electron microscopy(SEM).Although the surface of the fibers had no cracks,there was evidence of contaminations which affected the interfacial properties and the quality of the fibers.Results showed that the trends in the recovered and virgin fibers were similar with an increase in sizing concentration.The results highlighted the perspectives of increasing the quality of recovered fibers after the recycling process.

Experimental study on ductility improvement of reinforced concrete rectangular Columns retrofitted with a new fiber reinforced plastics method

Reinforced concrete （RC） columns lacking adequately detailed transverse reinforcement do not possess the necessary ductility to dissipate seismic energy during a major earthquake without severe strength degradation. In this paper, a new retrofit method, which utilized fiber-reinforced plastics （FRP） confinement mechanism and anchorage of embedded bars, was developed aiming to retrofit non-ductile large RC rectangular columns to prevent the damage of the plastic hinges. Carbon FRP （CFRP） sheets and glass FRP （GFRP） bars were used in this test, and five scaled RC columns were tested to examine the function of this new method for improving the ductility of columns. Responses of columns were examined before and after being retrofitted. Test results indicate that this new composite method can be very effective to improve the anti-seismic behavior of non-ductile RC columns compared with normal CFRP sheets retrofitted column.

Critical Thrust Force Forecasting for Drilling Exit Delamination of Carbon Fibre Reinforced Plastics

Exit delamination is excessive drilling thrust force.Therefore,it is necessary to investigate the critical thrust force which cause exit delamination when carbon fibre reinforced plastics(CRFP)is drilled.According to the linear elastic fracture mechanics,the mechanics of composite material and the classical thin plate bending theory,a common theoretical model of the critical drilling thrust force for CFRP plates is established.Compared with the experimental data of previous studies,the results show that the theoretical values agree well with the experimental values.This model can be used to forecast the critical thrust force for the drilling-induced delamination of CFRP.

Finite Element Analysis of the Steel Reinforced Plastic Pipe

The steel reinforced plastic pipe is a kind of green environmental protection pipelines with double-sides corrosionresisting and better withstanding to medium working pressure. The structure and technical process of this pipe are described briefly in this paper, and the finite element analysis has been done for the sake of understanding the distributions of stress and displacement inside this pipe under hydrostatic pressure. The analysis results are very important for safety application of the steel reinforced plastic pipe.

Feasibility study of wave-motion milling of carbon fiber reinforced plastic holes

Carbon fiber reinforced plastic(CFRP)has been applied in aeronautics,aerospace,automotive and medical industries due to its superior mechanical properties.However,due to its difficult-to-cut characteristic,various damages in twist drilling and chip removal clog in core drilling could happen,inevitably reducing hole quality and hole-manufacturing efficiency.This paper proposes the wave-motion milling(WMM)method for CFRP hole-manufacturing to improve hole quality.This paper presents a motion path model based on the kinematics of the WMM method.The wave-motion cutting mode in WMM was analyzed first.Then,comparison experiments on WMM and conventional helical milling(CHM)of CFRP were carried out under dry conditions.The results showed that the hole surface quality of the CFRP significantly improved with a decrease of 18.1%–36%of Ra value in WMM compared to CHM.WMM exerted a significantly weaker thrust force than that of CHM with a reduction of 12.0%–24.9%and 3%–7.7%for different axial feed per tooth and tangential feed per tooth,respectively.Meanwhile,the hole exit damages significantly decreased in WMM.The average tear length at the hole exit in WMM was reduced by 3.5%–29.5%and 35.5%–44.7%at different axial feed per tooth and tangential feed per tooth,respectively.Moreover,WMM significantly alleviated tool wear.The experimental results suggest that WMM is an effective and promising strategy for CFRP hole-manufacturing.

Microstructure of Carbon Fiber and Carbon Reinforced Plastic

This study is the investigation of the microstructure of different types of carbon fiber. They were compared with the carbonized and graphitized fibers. Results of structural researches have been presented. It was found that the damage varies from different pollution and the damage of the monofibers. The effect of the pollution of the monofiber was determined.

Square concrete columns strengthened with carbon fiber reinforced plastics sheets at low temperatures

Twenty-one square concrete columns were constructed and tested. The testing results indicate that bonded carbon fiber reinforced plastics(CFRP) sheets can be used to increase the strength and improve the serviceability of damaged concrete columns at low temperatures. The failure of the specimens,in most cases,takes place within the middle half of the columns. And the failure of strengthened columns is sudden and explosive. The CFRP sheets increase both the axial load capacity and the ultimate concrete compressive strain of the columns. The ultimate loads of strengthened columns at-10,0 and 10 ℃ increase averagely by 9.09%,6.63% and 17.83%,respectively,as compared with those of the control specimens. The axial compressive strength of strengthened columns is related to the curing temperatures. The improvement of axial compressive strength decreases with reducing temperature,and when the temperature drops to a certain value,the improvement increases with falling temperature.

EXTRUSION DIE CAE OF THE STEEL REINFORCED PLASTIC PIPE

The steel reinforced plastic pipe is a new kind of pressure pipe. It is made up with steelwires and plastic. Because reinforced skeleton of the steel wire increase the complexityof plastic flow during the extrusion phase, the traditional design criteria of extrusiondie is not suitable. The study on extrusion die of the kind of pipe is very importantstep in produce development. Using finite element (FE) method in this paper, theflow rule of molten plastic inside the die has been predicted and a groap of optimalstructural parameters was obtained. These results are helpful for reducing the designcycle and improve the quality of the final product.

Effect of Fibre Packing on Random Variability of Compressive Strength of Unidirectional Carbon Fibre Reinforced Plastic

Compression tests on twenty unidirectional(UD) carbon fibre reinforced plastic(CFRP) specimens are conducted, the statistics on the measured compressive strength is calculated, and the fracture surface is characterized. Two types of different fracture surface are experimentally observed, and they are corresponding to very different values on the compressive strength. A finite element(FE) analysis is conducted to investigate the influence of random fibre packing on the compressive strength. And a riks method(provided in ABAQUS software) is applied in FE model to analyze fibre buckling behaviour in the vicinity of compressive failure. The FE analysis agrees well with the experimental observation on the two types of buckling modes and also the partition of compressive strength. It is clearly shown that the random fibre packing lays a significant influence on the random variability of compressive strength of CFRP.

Behaviour of Multiscale Progressive Damage for Different Matrix Glass Fiber Reinforced Plastics Bars

The damage formation and evolution of glass fiber reinforced plastics( GFRP) bar on mechanical properties were mainly evaluated by theoretical analysis and numerical calculations which lack of test basis of damage process. The two different matrices of unsaturated polyester and vinylester GFRP bars were selected to carry out a series of macro-mesoscopic physical and mechanical tests to analyze the tensile progressive damage process on a multiscale. The formation of apparent crack,the bonding of internal components as well as the strain change were all reflected damage evolution of GFRP bar,and a certain correlation existed between them. Wherein the matrix has an obvious impact on the damage of bar,the component stress transfer effect of vinylester bar is better than unsaturated polyester from crack propagation observation and scanning electron microscopy( SEM). The cyclic loading tests quantitatively reflect the difference of damage accumulation between different matrix bars,and the failure load of bars decreases nearly 10%.

Tribological Behavior of Diamond Coatings against Carbon Fiber Reinforced Plastics under Dry Conditions

The frictional resistance and machining quality when cutting carbon fiber reinforced plastics (CFRP) laminates are associated with tribological behavior of tool materials. In the present study, the tribological properties of three types of monolayer microcrystalline diamond (MCD) coatings, nanocrystalline diamond (NCD) coatings and dual-layer MCD/NCD coatings sliding against CFRP are investigated under dry lubricated conditions using the rotational friction tester. The coefficients of friction (COF), wear rate and worn surfaces of the contacted surfaces are analyzed for the MCD-CFRP, NCD-CFRP and MCD/NCD-CFRP contacting pairs. The results show that compared with the monolayer MCD and NCD, the bilayer of MCD/NCD coating displays the lowest COF with the value of ~0.13, it is 42% and 55% of the values for MCD and NCD coatings. Due to the rough surfaces of MCD, the wear debris of CFRP on MCD samples exhibits the plowing effect. While for the NCD and MCD/NCD samples, the wear fragments display the planar shapes. The wear rate of CFRP against MCD is more than twice that of CFRP against NCD, due to the excellent loading capacity. While the wear rate of CFRP against MCD/NCD is about twice than that of CFRP-NCD pairs. The bilayer of MCD/NCD combines the excellent advantages of high hardness of MCD and the smooth surface of NCD. It shows the broad application potential for the bilayer coatings.

Dynamic Characteristics Analysis of Multilayer Fiber Reinforced Plastic Shaft

In order to study the dynamic characteristics of multilayer fiber reinforced plastic(MFRP)shaft,the coupling model of three-dimensional equivalent bending stiffness theory and transfer matrix method is established,and the influence of thickness-radius ratio,length-radius ratio,layer angles,layer proportion,and stacked approaches on MFRP shaft dynamic characteristics is investigated.The result shows that the proposed coupling model has high accuracy in MFRP shaft dynamic performance prediction.The proportion of small-angle layers is the decisive factor of MFRP shaft natural frequency.With the increase of thickness-radius ratio and length-radius ratio,the natural frequency of MFRP shaft decreases.The natural frequency of MFRP shaft with the angle layers combination of±45°and±90°is smaller compared with the metal shaft no matter in simple/free boundary condition or simple/simple supported boundary condition.

Advanced Welding Technology for Highly Stressable Multi-Material Designs with Fiber-Reinforced Plastics and Metals

Organic sheets made out of fiber-reinforced thermoplastics are able to make a crucial contribution to increase the lightweight potential of a design. They show high specific strength- and stiffness properties, good damping characteristics and recycling capabilities, while being able to show a higher energy absorption capacity than comparable metal constructions. Nowadays, multi-material designs are an established way in the automotive industry to combine the benefits of metal and fiber-reinforced plastics. Currently used technologies for the joining of organic sheets and metals in large-scale production are mechanical joining technologies and adhesive technologies. Both techniques require large overlapping areas that are not required in the design of the part. Additionally, mechanical joining is usually combined with “fiber-destroying” pre-drilling and punching processes. This will disturb the force flux at the joining location by causing unwanted fiber- and inter-fiber failure and inducing critical notch stresses. Therefore, the multi-material design with fiber-reinforced thermoplastics and metals needs optimized joining techniques that don’t interrupt the force flux, so that higher loads can be induced and the full benefit of the FRP material can be used. This article focuses on the characterization of a new joining technology, based on the Cold Metal Transfer (CMT) welding process that allows joining of organic sheets and metals in a load path optimized way, with short cycle times. This is achieved by redirecting the fibers around the joining area by the insertion of a thin metal pin. The path of the fibers will be similar to paths of fibers inside structures found in nature, e.g. a knothole inside of a tree. As a result of the bionic fiber design of the joint, high joining strengths can be achieved. The increase of the joint strength compared to blind riveting was performed and proven with stainless steel and orthotropic reinforced composites in shear-tests based on the DIN EN ISO 14273. Every specimen joined with the new CMT Pin joining technology showed a higher strength than specimens joined with one blind rivet. Specimens joined with two or three pin rows show a higher strength than specimens joined with two blind rivets.

Frequency Dependence of the <i>b</i>-Value Used for Acoustic Emission Analysis of Glass Fiber Reinforced Plastics

Acoustic Emission Testing (AT) is one of the major non-destructive testing methods used for severity evaluation of structures. Amplitude distributions of AE signals are characterized by b-value and the value is mainly used for the severity evaluation of concrete structures until now. The value is assumed to be independent with propagation distance between acoustic emission sources to AE sensors. We evaluate the influence of the wide frequency band encountered in the fracture behavior of glass fiber reinforced plastic (GFRP) on the b-value analysis. In tensile tests, the b-value was determined from an acoustic emission (AE) source generated near a centered hole in a specimen of GFRP. At 15 mm from the hole, the b-value analysis indicated a decreasing trend with increasing tensile stress. At a propagation length of 45 mm, farthest from the hole, a?small number of AE signals were received. The attenuation is more rapid for high-frequency AE signals. Thus, the amplitude distribution bandwidth is wide and the b-value changes. This change in b-value for GFRPs is investigated by analyzing the spectral components of the AE signals. For a single-frequency AE source, the b-value is unchanged with propagation length. In contrast, multiple-frequency AE sources produce changes in b-value proportional to the fraction of each spectral component in the received signal. This is due to the frequency dependence of the attenuation with propagation length.?From these results, the b-value analysis cannot be applied to considering frequency dependence of AE attenuation.