COMPOSITES SCIENCE AND ENGINEERING

EFFECT OF TPU NONWOVEN FABRIC ON PERMEABILITY FOR GLASS FIBER PREFORM AND TOUGHNESS PROPERTIES OF GF/EP COMPOSITES

ZHANG Na, LV Guang-chao, LIU Chun-tai, TAN Kun-lun

2019, 0(3): 5-10.

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In this study, the thermoplastic polyurethane nonwoven fabric (TNF) was chosen as structural toughening layer to improve the composite toughening, and the composites were fabricated by vacuum-assisted resin transfer molding (VARTM) technique. The toughening properties of the composites were investigated as well as permeability. Toughening of GF/EP composites was achieved by interleaving TNF. It provided the best all-round performance with fracture toughness improvements of 78% and 115% for mode-Ⅰ and mode-Ⅱ, respectively. At the same time, the permeability of TNF/GF/EP composites was decreased by 56.5%.

EXPERIMENTAL RESEARCH ON FATIGUE CHARACTERISTICS AND STRESS RELAXATION OF ADHESIVE ANCHORAGE SYSTEM FOR CFRP TENDON

ZHU Yuan-lin, LIU Li-hua, ZHOU Jia-qi, HUANG Sheng-bin

2019, 0(3): 11-15.

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The tensile fatigue and bending fatigue behaviour of CFRP tendon adhesive anchorage system were tested under three kinds of stress levels and stress amplitudes. The tensile strength of CFRP tendon anchorage system was tested after two million fatigue cycles. And the stress relaxation of CFRP tendon anchorage system was studied. Test results show that the CFRP tendon anchorage system developed is stable and reliable. The anchorage system is free of any damage after two million tensile fatigue or bending fatigue cycles. The tensile strength of CFRP tendon after fatigue test is almost unchanged, and the modulus increase by 4.3% in average. The model for predicting stress relaxation of CFRP tendon anchorage system was proposed and agreed with the measured values. The error in predicting the stress relaxation rate of the anchorage system for 1000 hours is 4.64%. The testing program for stress relaxation of CFRP tendon was proposed, and the stress relaxation rate of the CFRP tendon for 1000 hours is 0.67%, which could effectively avoid the effect of anchor adhesive deformation.

THE RESEARCH ON DAMAGE AND FAILURE MODES OF COMPOSITE L-JOINT

SHI Hao-nan, WANG Ji-hui, ZHANG Gui-ming

2019, 0(3): 16-20.

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The progressive damage model was established to simulate failure of a carbon fiber reinforced polymer matrix composite L-joint. A modified form of Hashin Damage and Apalak stiffness degradation were adopted to damage evolution of composite laminates, and cohesive element was adopted to simulate interlaminar damage initiation and the final failure were predicted. The results show that the progressive failure model can accurately simulate the tensile failure process of the L-joint, and the failure type mainly includes the crack of glue layer, the tensile failure of the matrix at the bottom of filler area and the delamination failure of the laminates.

STUDY ON THE PREPARATION AND INTERFACE PERFORMANCE OF O₃-OXIZED CARBON FIBER/POLYIMIDE COMPOSITES

ZHANG Rong, PEI Xue-liang, XI Xian-feng, OUYANG-Qin

2019, 0(3): 21-25.

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Carbon fiber, the surface of which was modified through ozone oxidation, was used as the reinforcement for thermoplastic polyimide resin. Effect of ozone treatment time on monofilament tensile strength and surface functional groups had been studied using monofilament tensile test and X-ray photoelectron spectroscopy (XPS), respectively. The results indicated that the mechanical properties of carbon fiber was destructed, and the oxygen-containing functional groups on the surface increased with the process of the ozone treatment. The composites were made by thermoplastic polyimide and carbon fiber oxidized with the high retention rate of monofilament tensile strength and high oxygen-containing functional groups, and the interlaminar shear strength was evaluated. The results show that compared with unoxidized specimen, the interlaminar shear strength of the composites made by thermoplastic polyimide and carbon fiber oxidized for 5 minutes increased by 43%, showing that ozone treatment can effectively enhance fiber-matrix interfacial bonding.

STUDY ON MECHANICAL BEHAVIOR OF COMPOSITE LAMINATE WITH CONTINUOUS LARGE CUTOUTS UNDER TENSION

WANG Li-li, FU Jian-wei, XUE Jun-chuan, LI Xin-xiang

2019, 0(3): 26-31.

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Large cutout was usually needed to meet the equipment installation, inspection and maintenance requirements when composite laminates were used as the main bearing components in aircraft structure. However, when the fibers were cut off, the local stress and deformation of the structure were discontinuous, which lead to stress concentration and cause complex mechanical behavior. Experiments and finite-element-method (FEA) had been conducted to investigate the deformation, load transmission and stress concentration behavior of a stiffened composite laminate with two large elliptical cutouts under tension. Damage mode and fracture load of the structure were predicted. The results indicate that strain distribution nearby the large cutouts of composite laminate is complicated. The damage will easily occur around the cutout area due to stress concentration and damage mode are diversified. Although the ultimate strength of the laminate is determined by fiber tensile damage and failure but the premature fiber extrusion damage caused by Poisson effect in cutout area cannot be ignored.

THE PREPARATION AND PERFORMANCE STUDY OF WOOD FLOUR REINFORCED POLYPROPYLENE COMPOSITE

ZHU Xiu-fang, ZHANG Jun, YANG Xu-yu, ZHANG Yi

2019, 0(3): 32-37.

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In this paper, the wood flours were treated with the silane coupling agent, and then mixed with the waste plastics, in which the majorority is polypropylene (PP). The wood meal reinforced PP composite was prepared in this way. The measurment on mechanical property and thermal property were performed by varing the grain size and content of wood meal in the composite, the recrystallization property of 20% (mass content) wood meal reinfored plastic was measured by the ultraviolet fluorescence test, and the results show that the mechanical property increased first and then decreased with the grain size and content of wood meal. The thermal property decreased with the content of wood meal. The crystallinity of PP matrix increased with the time exposing to the ultraviolet fluorescence.

LAYER SEQUENCE OPTIMIZATION FOR BUCKLING STRENGTH OF COMPOSITE LAMINATES

HUANG Li-hua, LIU Bo, SHI Ting-wei

2019, 0(3): 38-42.

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The optimal design of composite laminates is crucial for improving the bearing capacity of aircraft structures. In this paper, based on the genetic algorithm and the random normal distribution optimization algorithm, taking the buckling load of the axial compression composite laminates as the objective function, the optimal design of the layer sequence is carried out. Two optimization algorithms are programmed in MATLAB language to optimize the layer sequence of symmetrical balanced laminates with different layers and boundary conditions. The results show that the genetic algorithm with integer coding and penalty function can be used to optimize the sequence of laminated plate. For the 24-layer plates with pinned and fixed constraints, the failure loads of the optimal layers are increased by 27% and 15% than those of the worst layers, which demonstrates the obvious optimal effect. The results from the random normal distribution optimization algorithm are consistent with those from the genetic algorithm. Since the random normal distribution optimization algorithm is concise and easy to converge, it is more suitable for the optimal design of composite laminates in practice.

PREPARATION AND CERAMIZATION OF ZIRCONIUM AND SILICON CONTAINING ORGANIC PRECURSORS

YANG Ming-ze, ZHOU Quan, PENG Zheng-qiang, SONG Ning

2019, 0(3): 43-48.

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Zirconium-containing polymer (ZMP) with a main chain of-Zr-O-CH₂-CH- and an unsaturated group in the side was prepared by using zirconium n-propoxide, acetylacetone and 1,2-propanediol as raw materials of zirconium source. A silicon alkyne resin (PTSA) with a main chain of -SiH, -C≡C- was used as a silicon source. The two were reconstituted at a mass ratio of 2∶5 to obtain a ceramic precursor (PMS). The ZMP structure was characterized by FT-IR and NMR. The elemental composition of ZMP was analyzed by EDS. The curing behavior of PMS was investigated by DSC and in-situ infrared, and the heat resistance of PMS was studied by TGA. The TGA test shows that the precursor has good heat and thermal stability, and the mass retention rates at 1000 ℃ under nitrogen and air atmosphere are 90.24% and 88.53%, respectively. The ceramization evolution of PMS was studied by XRD, SEM, TEM and Raman. The ceramization evolution results show that the ceramic conversion rate of PMS at 1600 ℃ is as high as 57.4%, and the ceramic products contain high crystallinity ZrC and SiC crystals.

INFLUENCES OF FIBER WAVINESS ON MECHANICAL PROPERTIES OF INTERLAMINAR TOUGHENING CARBON FIBER/EPOXY COMPOSITE UNIDIRECTIONAL LAMINATE

XU Peng, GU Yi-zhuo, WU Chen-jun, GAO Long-fei

2019, 0(3): 49-54.

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In this study, interlaminar toughening carbon fiber /epoxy prepreg, i.e. X850, was adopted. Based on autoclave curing process, two kinds of unidirectional carbon fiber laminates with in-plane and out-of-plane waviness were fabricated by rolling prefabricated out-of-plane waviness and inserting prepreg strip into prepreg stack, respectively. The two kinds of fiber waviness defects in composites were characterized. In addition, tensile and compressive properties were measured and analyzed. The experimental results show that composite specimens containing different fiber waviness ratio (WR) were obtained with almost the same fiber content without other defects. For the range of prefabricated WR, the effect of out-of-plane wrinkling on tensile property can be neglected and compressive property decrease slightly. However, tensile and compressive properties are very sensitive to in-plane buckling. Their modulus, strength and failure mode change significantly, as WR increases. It is indicated that the type of fiber waviness is very important for evaluating this kind of defect.

STUDY ON THE EFFECT OF ACID TREATMENT ON THE PERFORMANCE OF BASALT FIBER ASPHALT

LIU Chun-bo, LIU Sheng

2019, 0(3): 55-60.

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In order to enhance the reinforcement and strengthening effect of basalt fiber (BF) in asphalt, surface treatment of BF by 1.0 mol/L and 2.5 mol/L HCL solution was performed. The surface morphology of BF was observed by environmental scanning electron microscopy (ESEM) and infrared spectroscopy. The results show that the surface of original BF was smooth, but the BF showed overall erosion after HCL solution treated. And the BF surface forms a silica gel layer, and the -OH content has increased. Conventional performance and tensile fracture morphology of the basalt fiber asphalt were characterized by softening point, 5 ℃ force-ductility and ESEM test. With the increase of HCL solution concentration and treatment time, the performance of BFA is firstly improved and then decreased. It can be clearly seen from tensile fracture morphology of BFA that the surface of BF treated with acid solution is coated with a thin asphalt film. And the best treatment time and concentration of HCL solution for BF erosion were 20 min, 2.5 mol/L.

DESIGN AND VERIFICATION OF AN AUTOMATIC FIBER HOLDING MECHANISM FOR FILAMENT WINDING MACHINE

TIAN Hui-fang, KANG Wei, ZHANG Yang, WU Ying-feng

2019, 0(3): 61-64.

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In view of the artificial hanging shear yarn phenomenon in the current filament winding process, an automatic yarn hanging mechanism applied to the filament winding machine is designed, and the key parts of the automatic clamping mechanism are tested. Glass fiber and carbon fiber prepreg belt used in industrial production were used as experimental materials. The effect of mechanism on yarn clamping was tested under dry yarn and soaking state respectively. The relationship between yarn sliding tensile force under different clamping forces was analyzed, and the clamping effect of the mechanism under dry yarn and soaking condition was compared. The experimental test results basically meet the demand of the fiber clamping force in the mechanism, which proves the feasibility of the mechanism scheme, and provides a reference for the improvement of the yarn hanging mechanism.

STUDY ON THE MOLDING TECHNOLOGY OF RTM FOR NORMAL REINFORCED PREFORM/PHENOLIC EXPANSION SECTION

ZHAO Wen-bin, TIAN Mou-feng, YAO Ya-lin, WANG Jing

2019, 0(3): 65-69.

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RTM technology can realize the near-net size forming of expansion section, and volume content of fiber can reach 53.1% to 59.9%. In this paper, the resin matrix, normal reinforced preform, inject equipment and mold involved in the preparation of normal reinforced preform/phenolic RTM expansion section were discussed. Phenolic resin as matrix, 2.5 D braided preform or needle punched preform as reinforcement to prepare composites through RTM process, and the related performance were analyzed. The results show that the interlaminar shear strength of expansion section is as high as 59.2 MPa, and the ablative erosion performance is improved significantly.

THE DESIGN AND MANUFACTURE TECHNIQUES OF BUS COMPOSITE-BODY MOULD

HUANG Shang-hong, LI Yi-quan, LI Rui-ying, WU Jian-dan

2019, 0(3): 70-75.

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This paper makes a detailed exposition on composite bus-body mould design and manufacture technology by referencing the former experience on engineering. Then the performance testing of mould products was introduced. A variety of structure and function design are used in the process of making the mould, such as stiffness reinforced structure, demolding device consist of lifting mechanism and insert blocks, temperature field stability control system, double vacuum suction system, and sliding surface adjustment system etc. The key points were introduced during manufacturing process, and the testing result of the performance reveal that this mould can meet every technical requirement. Finally, the final service properties can fulfill the requirements of customers well, which verified the feasibility of the design and manufacture technology.

EVOLUTION OF CARBONIZATION PERFORMANCE OF HIGH CARBON PHENOLIC RESIN AND ITS COMPOSITES

SHU Chang-peng, YANG Peng-ao, SHI Zheng-tang, ZHOU Quan

2019, 0(3): 76-81.

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As one of the precursors for the preparation of C/C composites, carbon fiber reinforced phenolic resin matrix composites have been widely used in almost every aspect of modern industry nowadays. Studying the carbonization performance of a novel high-carbon phenolic resin and its composites can effectively promote the production and application C/C composites. We investigated the carbonization properties of high carbon phenolic resin and its composites under different temperatures. It shows that high carbon phenolic resin has the same structure as normal phenolic resin. At 199 ℃, the solidification of high carbon phenolic resin can reach the fastest rate. TGA test result shows that this resin has higher carbon residue rate at 1000 ℃ in N₂. The carbonization properties of this resin and its carbon fiber reinforced composites were also studied. The results show that high carbon phenolic resin has a higher residual carbon ratio than the ordinary phenolic resin. Only when the temperature exceeds 1000 ℃, the carbonization process of this resin can be fully carried out. However, when the carbonization temperature is too high, the decomposed same carbon particles will deposit into larger one. Of course, these particles contains only a very small amount of graphite grains, and most of them are amorphous and irregular. Similarly, when it comes to its composites, the large particles produced at higher temperatures will influence the contents of apparent and closed porosities in composites. When the composites are carbonized under 1000 ℃, they can obtain the best apparent porosities. This is benefit for their subsequent processes.

ICE-SHEDDING INDUCED VIBRATION OF A COMPOSITE CROSS ARM TOWER-LINE SYSTEM

QIU Yong, YU Jie, ZHAO Hua-yun

2019, 0(3): 82-85.

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This paper is proposed to analyze the dynamic response of the tower-line system subject to ice shedding. The existing steel cross arms and the improved composite ones are to be analyzed. The before and after improvement of finite element models for a four-span transmission line system are built by ANSYS. The overhead conductor with ice-coating and ice-shedding are simulated by using the modifying density method. The results show that composite cross arm tower can effectively increase electrical safety distance when the conductor jumps with ice shedding and prevent flashover accident. Furthermore, by selecting appropriate length of electrical fittings, the adverse impact of ice shedding on the composite cross arm can be effectively reduced.

INFLUENCE OF X-RAY CT IMAGING DETECTION METHOD ON TESTING RESULTS OF DELAMINATION DEFECTS IN COMPOSITE MATERIAL

DONG Fang-xu, WANG Cong-ke, FAN Li-mei, ZHAO Fu-bao

2019, 0(3): 86-91.

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Three kinds of X-ray CT imaging detection methods including X-ray tomography CT imaging detection method, X-ray spiral CT imaging detection method and X-ray cone beam CT imaging detection method were used to detect carbon fiber matrix composites with prefabricated mechanical processing simulated delamination defects. These X-ray CT imaging detection methods are compared from three aspects, i.e., detection speed, image quality and defect resolution. The results show that the detection method of X-ray cone beam CT imaging has the highest detection efficiency, the best image quality and the smallest defect size measurement error in the detection of delamination defects in composite materials. It provides a reference for the selection of other defects in composite materials.

RESEARCH PROGRESS OF ALIGNED GRAPHENE REINFORCED POLYMER COMPOSITES

YANG Shi-xuan, JIAO Wei-cheng, CHU Zhen-ming, ZHANG Chen-wei

2019, 0(3): 92-100.

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The introduction of carbon nanomaterials, such as graphene, in the resin matrix can significantly improve the mechanical properties, thermal conductivity and versatility of the composites, consequently introducing innovation into the traditional composites. The orientation of nanomaterial in composites will directly affect the properties of the composites. According to the data in literatures, compared to randomly oriented nanocomposites, the strength of graphene/polymer composites reinforced with aligned graphene is 50% higher, and the thermal conductivity of those is approximately 100% higher. What is more, the aligned graphene reinforced polymer composites can see an increase in toughness by approximately 1.2 times compared to randomly aligned graphene reinforced polymer composites. In this regard, this paper summarizes the preparation methods of aligned-graphene/polymer composites, including layer-by-layer self-assembly method, flow-shear induced orientation method, vacuum-assisted self-assembly method, external field induced orientation method, etc., and briefly describes the advantages and disadvantages of each preparation method. The enhancement in the mechanical property, thermal conductivity and electrical conductivity of the composites caused by aligned graphene is analyzed. On this basis, the development and prospects of the development of aligned-graphene/polymer nanocomposites are discussed.

PROGRESS IN NUMERICAL SIMULATION OF CFRP MACHINING PROCESS

FANG Chun-ping, ZHAO Jin-ze, LI Zhan-shu, LING Li

2019, 0(3): 101-104.

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Carbon Fiber Reinforced Polymer (CFRP) has been widely used in aircraft and aerospcace industries due to its execlllent comprehensive performance. Recently, numerical simulation technonlogy has played an important role in the investigation of machining process, pramateres optimization and material removal mechanism of CFRP. This paper reviews the progress of numerical simulation in maching process of CFRP by analyzing and discussing the research and application in the aspects of cutting force, surface integrity and damage mechanism at home and abroad. A preliminary forecast on the future development direction of the numerical simulation about CFRP was made.

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