共查询到20条相似文献,搜索用时 15 毫秒
1.
Shirley Zhiqi Shen Stuart BatemanPatrick McMahon Mel Dell’OlioJanuar Gotama Tri NguyenQiang Yuan 《Composites Science and Technology》2010
The effects of small amount of organically modified Clay (Clay) in polyamide 6 (PA6) on fire performance and thermal mechanical properties of Clay/PA6/woven glass fibres (GF) laminates are investigated by cone calorimeter test, dynamic mechanical thermal analysis (DMTA), and heat distort temperature (HDT) measurement. The mechanical properties, such as tensile and flexural properties of Clay/PA6 composites and Clay/PA6/GF laminates were also measured. Up to 3 wt.% Clay in a Clay/PA6/GF laminate with fibre volume fraction of 30 vol.% delayed the ignition time and peak heat release rate (PHRR) time by 55% and 118%, respectively, even though the value of the PHRR or the HDT was not significantly affected. 2 wt.% Clay increased flexural modulus and strength of the Clay/PA6/GF laminate by 10% and 16%, respectively, but more Clay did not increase the mechanical properties accordingly. Small amount of Clay does not affect glass fibre dominated properties, such as HDT, but do affect matrix dominated properties, and significantly affect the fire performance in terms of delaying ignition time and PHRR time. Optimization of laminate making process could benefit from additions of more Clay, therefore further improve fire performance and enhance mechanical properties. 相似文献
2.
I. Dlouhy Z. Chlup D. N. Boccaccini S. Atiq A. R. Boccaccini 《Composites Part A》2003,34(12):1177-1185
The thermal aging of a glass matrix composite reinforced by short carbon fibres as well as by ZrO2 particles (hybrid composite) was investigated at temperatures in the range 500–700 °C for exposure durations of 24 h in air. The mechanical properties of as-received and aged samples were evaluated at room temperature by using the three-point flexure chevron notch technique. The fracture toughness values of as-received specimens were in the range 2.6–6.4 MPa m1/2. Fracture toughness was affected by the thermal aging conditions. For thermal aging at temperatures <700 °C, degradation of fibre–matrix interfaces occurred and therefore the apparent fracture toughness and flaw tolerant resistance decreased. For the most severe ageing conditions tested (700 °C/24 h), fracture toughness values dropped to 0.4 MPa m1/2. Significant degradation of the material was detected for this aging condition, mainly characterised by porosity formation in the matrix as a result of softening of the glass and oxidation of the carbon fibres. 相似文献
3.
Zhenyang YuNaiqin Zhao Enzuo LiuChunsheng Shi Xiwen DuJian Wang 《Composites Part A》2012,43(4):631-634
Aluminum matrix composite reinforced by in situ generated single crystalline MgAl2O4 whiskers was fabricated by chemical synthesis method in an Al-Mg-H3BO3 system. A large number of MgAl2O4 whiskers were generated during the sintering process and distributed homogeneously in the Al matrix. The whiskers penetrate into the matrix grains to form the framework of the materials, leading to an incredible increase in mechanical properties of the composites. The generation mechanism of the MgAl2O4 whiskers was also discussed. 相似文献
4.
Effect of carbon nanofibers (CNFs) content on thermal and mechanical properties of CNFs/SiC nanocomposites 总被引:1,自引:0,他引:1
Carbon nanofibers dispersed β-SiC (CNFs/SiC) nanocomposites were prepared by hot-pressing via a transient eutectic phase route at 1900 °C for 1 h under 20 MPa in Ar. The effects of additional CNFs content between 1 and 10 wt.% were investigated, based on densification, microstructure, thermal and mechanical properties. The CNFs/SiC nanocomposites by the CNFs contents below 5 wt.% exhibited excellent relative densities over 98% with well dispersed CNFs. However, the CNFs/SiC nanocomposites containing the CNFs of 10 wt.% possessed a relative density of 92%, accompanying CNFs agglomerates and many pores located inside the agglomerates. The three point bending strength gradually decreased with the increase of CNFs content, but the indentation fracture toughness increased to 5.7 MPa m1/2 by the CNFs content of 5 wt.%. The thermal conductivity was enchanced with the increase of CNFs content and represented a maximum value of 80 W/mK at the CNFs content of 5 wt.%. 相似文献
5.
Zhiqi Shen Stuart BatemanDong Yang Wu Patrick McMahonMel Dell’Olio Januar Gotama 《Composites Science and Technology》2009
This paper presents a preliminary investigation on the effects of incorporating carbon nanotubes (CNT) into polyamide-6 (PA6) on mechanical, thermal properties and fire performance of woven glass reinforced CNT/PA6 nanocomposite laminates. The samples were characterized by tensile and flexural tests, thermal gravimetric analysis (TGA), heat distortion temperature (HDT) measurements, thermal conductivity and cone calorimeter tests. Incorporation of up to 2 wt% CNT in CNT/PA6/GF laminates improved the flexural stress of the laminates up to 36%, the thermal conductivity by approximately 42% and the ignition time and peak HRR time was delayed by approximately 31% and 118%, respectively. 相似文献
6.
I. Montealegre Melendez E. NeubauerP. Angerer H. DanningerJ.M. Torralba 《Composites Science and Technology》2011,71(8):1154-1162
The goal of this work is the evaluation of nanoscaled reinforcements; in particular nanodiamonds (NDs) and carbon nanotubes (CNTs) on properties of titanium matrix composites (TiMMCs). By using nano sized materials as reinforcement in TiMMCs, superior mechanical and physical properties can be expected. Additionally, titanium powder metallurgy (P/M) offers the possibility of changing the reinforcement content in the matrix within a very wide range. In this work, TiMMCs have been produced from titanium powder (Grade 4). The manufacturing of the composites was done by hot pressing, followed by the characterisation of the TiMMCs. The Archimedes density, hardness and oxygen content of the specimens in addition to the mechanical properties were compared and reported in this work. Moreover, XRD analysis and SEM observations revealed in situ formed titanium carbide (TiC) phase after hot pressing in TiMMCs reinforced with NDs and CNTs, at 900 °C and 1100 °C respectively. The strengthening effect of NDs was more significant since its distribution was more homogeneous in the matrix. 相似文献
7.
Polypropylene composites were prepared from three different PP matrices, a homopolymer, a random and a heterophase copolymer, and corn cob to study the effect of matrix characteristics on deformation and failure. The components were homogenized in an internal mixer and compression molded to 1 mm thick plates. Mechanical properties were characterized by tensile testing, while micromechanical deformations by acoustic emission measurements and fractography. The results proved that the dominating micromechanical deformation process may change with matrix properties. Yield stress determined from the stress vs. strain traces may cover widely differing processes. Debonding is the dominating process when the adhesion of the components is poor, while matrix yielding and/or filler fracture dominate when adhesion is improved by the introduction of a functionalized polymer. The dominating deformation mechanism is determined by component properties and adhesion. Interfacial adhesion, matrix yield stress and the inherent strength of the reinforcement can be limiting factors in the improvement of composite strength. The properties of polymer composites reinforced with lignocellulosic fillers are determined by micromechanical deformation processes, but they are independent of the mechanism of these processes. 相似文献
8.
A alumina borate whisker with Bi(OH)3 coating was prepared by a chemical method. The coated whiskers were sintered at various temperatures. The coated whisker-reinforced pure aluminum matrix composite was fabricated by squeeze casting method. The microstructures of the coated whiskers and coated composites with the different sintering temperature of whisker preform were studied, and the tensile properties of the coated composites at room temperature were also investigated. It can be found that the microstructures of coatings on the whisker surfaces and at the interface in the coated composites are strongly dependent on the sintering temperature of whisker preform. The ultimate tensile strength and elongation to fracture of the coated composites increased with the increasing of sintering temperature of the whisker preform. 相似文献
9.
The microstructure, hardness, fracture toughness and thermal shock resistance were investigated for 15 vol.% TiC0.3N0.7 whisker reinforced β-sialon (Si6−zAlzO2N8−z with z=0.6) composites with additions of three different volume fractions 2, 5 and 20 vol.%, of an yttrium-containing glass oxynitride phase. The composites were prepared by hot pressing at 1750°C for 90 min under a uniaxial pressure of 30 MPa in nitrogen atmosphere. The TiC0.3N0.7 whiskers were found to survive without deteriorating in morphology or reacting with the β-sialon matrix and/or the glass phase. The TiC0.3N0.7 whiskers had no obvious influence on the matrix microstructure, but their presence improved both the hardness and the fracture toughness of the composites. The highest hardness was obtained for the whisker composite with 2 vol.% glass phase (Hv=18.6 GPa). The fracture toughness and thermal shock resistance improved with increasing glass content. The whisker reinforced composite containing 20 vol.% glass showed the highest fracture toughness (K1C=6.8 MPa m1/2). No unstable crack extension occurred during the thermal shock test of the obtained composites in the temperature interval 90-700°C, but above 700°C severe oxidation of the whiskers precludes further evaluation of thermal shock properties by the indentation-quench method applied. 相似文献
10.
J.M.L. Reis D.C. MoreiraL.C.S. Nunes L.A. Sphaier 《Materials Science and Engineering: A》2011,528(18):6083-6085
The present paper examines the mechanical properties of polymer mortar (PM), with different weight fraction of nano-Al2O3 and nano-Fe2O3. The results showed that flexural and compressive strength measured of PM filled with nanoparticles were lower than plain polymer mortar but a considerably stiffness increase was observed for all formulations tested. 相似文献
11.
Charles D. Wood Marc J. Palmeri Karl W. Putz Gregory Ho Rick Barto L. Catherine Brinson 《Composites Science and Technology》2012
Carbon nanotubes (CNTs) were grown from the surface of glass fibers by chemical vapor deposition, and these hybrid fibers were individually dispersed in an epoxy matrix to investigate the local composite structure and properties near the fiber surface. High-resolution transmission electron microscopy revealed the influence of infiltration and curing of a liquid epoxy precursor on the morphology of the CNT “forest” region, or region of high CNT density near the fiber surface. Subsequent image analysis highlighted the importance of spatially dependent volume fractions of CNTs in the matrix as a function of distance from the fiber surface, and nanoindentation was used to probe local mechanical properties in the CNT forest region, showing strong correlations between local stiffness and volume fraction. This work represents the first in situ measurements of local mechanical properties of the nano-structured matrix region in hybrid fiber-reinforced composites, providing a means of quantifying the reinforcement provided by the grafted nanofillers. 相似文献
12.
Heitor Luiz Ornaghi Jr. Sandro Campos Amico 《Materials Science and Engineering: A》2011,528(24):7285-7289
This study aims to evaluate the performance of curaua/glass hybrid composites focusing on mechanical and dynamic mechanical analysis (DMA). Composites with distinct glass/curaua fiber loading ratios were studied. Flexural strength and modulus, impact strength and Barcol hardness increased for higher glass fiber content. The same was found for storage and loss modulus. The activation energy of the relaxation process in the glass transition region showed a maximum for the all-glass composite, corroborating with the results of concentration of elastic chains (υe). Cole-Cole plots were obtained and found to follow the same trend regardless of the glass content, whereas peak height and peak width at half-height were maximum for the all-glass composite. 相似文献
13.
A micromechanics model of the thermomechanical constitutive behavior and micro-structural inhomogeneity of carbon nanotubes (CNTs)/shape memory polymer (SMP) composites is presented. It is assumed that the CNTs are elastic and the SMP obeys a thermomechanical constitutive law. The effective properties of CNT/SMP composites are examined using a micro-mechanics method. The effect of CNT aggregation in the composite, frequently encountered in real engineering situations, is studied. The degree of aggregation is described by an aggregation coefficient, and the effective properties of SMP composites with aggregated CNTs are calculated using a stepping scheme. It is shown that the degree of CNT aggregation dramatically influences the effective properties of the CNT/SMP composites. A homogeneous microstructure leads to maximum levels of effective composite properties. 相似文献
14.
A flame retardant efficiency of flame retardants; ammonium polyphosphate (APP), magnesium hydroxide (Mg(OH)2), zinc borate (Zb), and combination of APP with Mg(OH)2 and Zb in sisal fiber/polypropylene (PP) composites was investigated using a horizontal burning test and a vertical burning test. In addition, maleic anhydride grafted polypropylene (MAPP) was used as a compatibilizer to enhance the compatibility in the system; i.e. PP-fiber and PP-flame retardants. Thermal, mechanical, and morphological properties of the PP composites were also studied. Adding the flame retardants resulted in improved flame retardancy and thermal stability of the PP composites without deterioration of their mechanical properties. APP and combination of APP with Zb effectively enhanced flame retardancy of the PP composites. No synergistic effect was observed when APP was used in combination with Mg(OH)2. SEM micrographs of PP composites revealed good distribution of flame retardants in PP matrix and good adhesion between sisal fiber and PP matrix. 相似文献
15.
The present paper developed a three-dimensional (3D) “tension–shear chain” theoretical model to predict the mechanical properties of unidirectional short fiber reinforced composites, and especially to investigate the distribution effect of short fibers. The accuracy of its predictions on effective modulus, strength, failure strain and energy storage capacity of composites with different distributions of fibers are validated by simulations of finite element method (FEM). It is found that besides the volume fraction, shape, and orientation of the reinforcements, the distribution of fibers also plays a significant role in the mechanical properties of unidirectional composites. Two stiffness distribution factors and two strength distribution factors are identified to completely characterize this influence. It is also noted that stairwise staggering (including regular staggering), which is adopted by the nature, could achieve overall excellent performance. The proposed 3D tension–shear chain model may provide guidance to the design of short fiber reinforced composites. 相似文献
16.
In recent years, many tidal turbine projects have been developed using composites blades. Tidal turbine blades are subject to ocean forces and sea water aggressions, and the reliability of these components is crucial to the profitability of ocean energy recovery systems. The majority of tidal turbine developers have preferred carbon/epoxy blades, so there is a need to understand how prolonged immersion in the ocean affects these composites. In this study the long term behaviour of different carbon/epoxy composites has been studied using accelerated ageing tests. A significant reduction of composite strengths has been observed after saturation of water in the material. For longer immersions only small further changes in these properties occur. No significant changes have been observed for moduli nor for composite toughness. The effect of sea water ageing on damage thresholds and kinetics has been studied and modelled. After saturation, the damage threshold is modified while kinetics of damage development remain the same. 相似文献
17.
Cobalt-coated Al2O3 and TiC powders were prepared using an electroless method to improve resistance to thermal shock. The mixture of cobalt-coated Al2O3 and TiC powders (about 70 wt.% Al2O3-Co + 30 wt.% TiC-Co) was hot-pressed into an Al2O3-TiC-Co composite. The thermal shock properties of the composite were evaluated by indentation technique and compared with the traditional Al2O3-TiC composite. The composites containing 3.96 vol.% cobalt exhibited better resistance to crack propagation, cyclic thermal shock and higher critical temperature difference (ΔTc). The calculation of thermal shock resistance parameters (R parameters) shows that the incorporation of cobalt improves the resistance to thermal shock fracture and thermal shock damage. The thermal physic parameters are changed very little but the flexure strength and fracture toughness of the composites are improved greatly by introducing cobalt into Al2O3-TiC (AT) composites. The better thermal shock resistance of the composites should be attributed to the higher flexure strength and fracture toughness. 相似文献
18.
M. RagoubiB. George S. MolinaD. Bienaimé A. MerlinJ.-M. Hiver A. Dahoun 《Composites Part A》2012,43(4):675-685
In this study, we investigated the mechanical and thermal properties of composites based on miscanthus fibres and poly lactic acid or polypropylene matrices. The treatment of fibres by corona discharge which results in a surface oxidation and an etching effect as shown by X-ray photoelectron spectroscopy and scanning electron microscopy, leads to an improvement of the interfacial compatibility between matrix and fillers. Hence the homogeneity of materials (checked by X-ray tomography and fractographic evaluation) is better, the mechanical properties measured by classical tensile tests are improved (Young moduli increase around 10-20%). Dynamic mechanical analysis performed on samples leads to similar conclusions (higher modules and slight increase of glass transition temperature hence restricted molecular movement). The thermal stability of composites was investigated by thermogravimetric analysis. While the incorporation of raw fibres leads to a slight decrease of decomposition temperature, it is systematically increased as soon as fillers have been treated. 相似文献
19.
Microcapsules containing phase change materials (microPCMs) can be filled in polymeric matrix forming smart temperature-controlling composites. The aim of this study was to investigate the effect of interface debonding on the thermal conductivity of microPCMs containing paraffin/epoxy composites. The shell thickness and average size of microPCMs were controlled by regulating the core/shell ratios and emulsion stirring rates. Test results indicated that the thermal conductivity (Ke) of all composites decreased after a thermal shock treatment. SEM and thermography measurements were applied to observe the interface behaviors of composites after a violent thermal treatment process. It was proved that the interface debonding was generated because of the mismatch of expansion coefficient between shell and epoxy. A modeling analysis of the relative thermal conductivity (Kr) indicated that the effective approach to decrease the debonding is to enhance the molecule tangling degree between shell and matrix. 相似文献
20.
In this paper several bidirectional flax fibers, usually used to made curtains, were employed as reinforcement of an epoxy matrix. Four different laminates were made by a vacuum bagging process, with varying both the areal weight and the treatment of the fabric. 相似文献