Reinforcement and quantitative description of inorganic particulate-filled polymer composites

Understanding the reinforcing mechanisms should be meaningful for preparation of new polymer composites. The reinforcing mechanisms of the inorganic particulate-filled polymer composites were analyzed and discussed in the present paper, and concluded several reinforcing theories on the basis of the previous studies, such as interfacial adhesion reinforcing theory, filler inducing crystallization reinforcing theory, filler frame reinforcing theory, and synergistic reinforcing effect theory. The reinforcing effects should be related closely to the filler shape and size, in addition to the filler concentration and dispersion in the matrix. Consequently, to describe accurately the reinforcing mechanisms of the composites, two or more reinforcing theories should be used for the actual composite system, and one of among them should be usually as the major reinforcing mechanism. Finally, the quantitative characterization of the reinforcement was described.     

A predictive model for particulate-filled composite materials

A predictive model for particulate-filled composite materials has been developed. The model uses a combination of finite element analysis and spatial statistical techniques; this combination allows the results from finite element analysis to be applied to real materials. The model is applied to epoxy resin filled with glass spheres. Predicted values of stiffness are compared with experimental measurements, and excellent agreement is found. The model is used to investigate stress distributions and the results are compared with experimental observations of fracture under varying conditions; the fracture behaviour of these materials is significantly elucidated.     

A constitutive model for self-reinforced ductile polymer composites

Self-reinforced polymer composites are gaining increasing interest due to their higher ductility compared to traditional glass and carbon fibre composites. Here we consider a class of PET composites comprising woven PET fibres in a PET matrix. While there is a significant literature on the development of these materials and their mechanical properties, little progress has been reported on constitutive models for these composites. Here we report the development of an anisotropic visco-plastic constitutive model for PET composites that captures the measured anisotropy, tension/compression asymmetry and ductility. This model is implemented in a commercial finite element package and shown to capture the measured response of PET composite plates and beams in different orientations to a high degree of accuracy.     

聚合物复合材料的新进展

论述了聚合物复合材料应用概况及品种发展,如玻璃钢领域聚合物复合材料消费结构,航空航天用高性能复合材料,汽车用PP纳米复合材料,生物可降解PU复合材料,树脂基超杂复合材料,聚合物-纳米粘土复合塑料,木塑复合材料等.并介绍了可降低复合材料制造成本的真空辅助成型技术.     

非层状纳米无机粒子/热塑性聚合物复合材料制备方法研究进展

纳米粒子由于十分容易聚集和团聚, 加之表面亲水性的纳米颗粒和表面憎水性的聚合物基体的相容性较差, 往往以较大的团聚体形式分散于聚合物基体树脂中, 导致复合材料的性能不佳。基于常规共混法的纳米颗粒/聚合物复合材料制备技术仍是重要的制备途径之一, 关键在于如何解决复合体系中纳米粒子的有效分散和利用问题。为此, 本文中针对非层状纳米无机粒子/热塑性聚合物复合材料的制备, 介绍了纳米无机粒子表面改性和纳米颗粒在热塑性聚合物中的分散技术方面的研究进展。      

Laser ablation protection of polymer matrix composites by adhesive inorganic coatings

Further utilization of polymer matrix composites (PMCs) in the aerospace industry is threatened by the development of laser weapons, resulting from weak oxidation resistance, low operation temperature and poor anti-laser ablation performance of the PMCs. Preparing an adhesive inorganic coating on the surface of components is an effective method to improve the laser irradiation resistance. Anti-laser ablation coatings composed of ZrO₂ as pigment and sodium silicate as binder with different curing agents (including SiO₂ and Na₂SiF₆) are fabricated on the PMCs substrate with brush painting. Influence of the different curing agents on anti-laser ablation of the coatings at the laser wavelength of 1064 nm is investigated. The rear surface temperature of substrate with coatings, containing SiO₂ and Na₂SiF₆, decreases from 240 to 60 and 70 °C, respectively, when testing at 1000 W for 5 s. After irradiation test at 1000 W for 10 s, the coating with SiO₂ as curing agent shows slight molten state on the surface, while the coating with Na₂SiF₆ is broke down, because coating containing SiO₂ possesses more compact microstructure and fewer cracks than that with Na₂SiF₆.     

A thermodynamic heat transfer model for intumescent systems

A mathematical model has been developed which describes the various physical processes of an intumescent system by considering mass and energy control volumes. Expansion is explicitly accounted for by assuming it to be a function of mass loss. Thermodynamic data from thermogravimetric analysis and differential scanning calorimeter characterizes the chemical constituents of the coating. A computer program has been written to solve the system of equations, with appropriate boundary conditions, as a function of time. Model predictions are compared against experimental data.     

Electrical and mechanical properties of aluminosilicate inorganic polymer composites with carbon nanotubes

The DC electrical conductance of potassium aluminosilicate inorganic polymers (geopolymers) containing up to 6 wt% single-wall carbon nanotubes has been determined as a function of temperature up to 340 °C. After removal of the processing water during the first heating cycle, the conductance in subsequent heating cycles increases as a function of carbon nanotube content and temperature from 9.75 × 10⁻⁴ to 1.87 × 10⁻³ S m⁻¹ in the composites containing 0 and 0.2 wt% carbon nanotubes, respectively, at 290 °C. By comparison, the electrical conductance of potassium inorganic polymer composites containing graphite was generally lower. The conductance activation energies of the carbon nanotube and graphite composites were similar, and decreased from about 55 to 5 kJ mole⁻¹ with increasing carbon content. The tensile strengths of carbon nanotube and graphite-containing potassium geopolymer composites, determined by the Brazil method on 10–12 replicates, were about 2 MPa, and showed little change with increasing carbon nanotube content up to 0.3 wt%. By contrast, the tensile strengths of an analogous set of sodium composites were up to four times greater, possibly reflecting the necessity for less processing water in the synthesis of the sodium samples.     

Preparation and characterization of polymer/inorganic nanoparticle composites through electron irradiation

In this paper, we report a new method to prepare the polymer/inorganic nanoparticle composites using electron irradiation-induced polymerization. The mixture of nanoparticles and MMA solution were co-irradiated by 1.6 MeV electron beam to a dose of 10, 20 and 30 kGy at a dose-rate of 60 kGy/h in air at room temperature. The products after irradiation were extracted using a soxhlet extractor with boiling xylene and investigated by X-ray diffraction (XRD), Fourier transmission infrared (FTIR), X-ray photoelectron spectroscopy (XPS), optical absorption spectra (OAP) and photoluminescence (PL). The FTIR and XPS results show that there exist some unextractable PMMA in the nanocomposites after extraction, indicating a strong interaction between the PMMA and nanoparticles. PL results show that new luminescence peaks appear at 415 and 420 nm for the nanocomposites of anatase and γ-Al₂O₃.     

A new model for flow boiling heat transfer coefficient inside horizontal tubes with twisted-tape inserts

This paper presents a new method to predict the heat transfer coefficient during flow boiling inside horizontal tubes containing twisted tape inserts. The method was developed based on the database presented by Kanizawa et al. This database comprises flow boiling results for horizontal tubes with internal diameters of 12.7 and 15.9 mm, twisted-tape ratios of 3, 4, 9 and 14, mass velocities ranging from 75 to 200 kg m⁻² s⁻¹, heat fluxes of 5 and 10 kW m⁻² and saturation temperatures of 5 and 15 °C. The method is flow-pattern based and considers flow boiling, dryout and mist flow regions. The predictive method also takes into account the physical picture of the swirl flow phenomenon by considering swirl flow effects promoted by the twisted tape insert. The proposed method provides satisfactory predictions and captures the main heat transfer trends of the data of Kanizawa et al. and also of independent data from literature.     

离子聚合物金属复合材料电致动模型研究

离子聚合物金属复合材料（ionic polymer-metal composites,IPMC）是一种新型电致形变高分子材料,具有广阔应用前景。为了有效描述IPMC的形变规律,基于IPMC致动原理提出了一种电致动模型。建立了阶梯电压下IPMC膜内水合阳离子的力平衡方程,由水合阳离子的浓度分布及水分子的扩散计算得出水分子的浓度以及含水量分布,结合实验所确定的含水量和应变的关系从而确定IPMC沿厚度方向的应变分布。该计算方法适用于不同形状的IPMC致动器。以悬臂梁IPMC致动器为例,通过应变分布计算得到IPMC致动器在阶跃电压下的输出弯矩和相应的位移响应,模拟结果与实验结果的瞬时响应规律高度一致,证明该模型正确。该模型的建立为IPMC结构驱动一体化设计奠定了坚实的基础。     

A new data reduction scheme for the fragmentation testing of polymer composites

A new reduction scheme of fragmentation data for the derivation of interfacial mechanical properties in polymer composites is proposed. The scheme is based on a theoretical model that accounts for elastic load transfer and friction at the interface, as well as for the statistical nature of fibre strength. Interface mechanical behaviour is characterized by two independent parameters, namely the interface bond strength and interface frictional resistance. Derived values of the two interface properties are computed, such that they yield the best possible agreement between experimental and theoretical results for the evolution of fibre fragment aspect ratio and debonding ratio as a function of applied strain. Results are reported for carbon fibres embedded in an epoxy matrix, with different levels of fibre surface treatment.     

A mathematical model of heat transfer for forced-convective film boiling

A mathematical model of film boiling with forced convection of the liquid is discussed. A solution is obtained on a computer and is represented in the form of nomographs and approximation relations. The computed results are compared with experimental data.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 33, No. 5, pp. 822–827, November, 1977.     

Theoretical-experimental study of complex heat transfer in highly porous composites

A probabilistic approach is proposed for modeling the physical characteristics of high-porosity randomly nonuniform media. The results of mathematical modeling of complex heat transfer are compared with experimental data.Translated from Inzhenerno-fizicheskii Zhurnal, Vol. 59, No. 4, pp. 554–561, October, 1990.     

Micromechanical modeling of particulate-filled composites using micro-CT to create representative volume elements

International Journal of Mechanics and Materials in Design - A method based on X-ray micro-CT was introduced to create realistic representative volume elements (RVE) for particulate-filled...     

Recycling of shredded composites from wind turbine blades in new thermoset polymer composites

As the energy produced from wind increases every year, a concern has raised on the recycling of wind turbine blades made of glass fibre composites. In this context, the present study aims to characterize and understand the mechanical properties of polyester resin composites reinforced with shredded composites (SC), and to assess the potential of such recycling solution. A special manufacturing setup was developed to produce composites with a controlled content of SC. Results show that the SC in the composites was well distributed and impregnated. The composite stiffness was well predicted using an analytical model, and fibre orientation parameters for strength modelling were established. The stress-strain curves revealed composite failure at unusual low strain values, and micrographs of the fracture surface indicated poor adhesion between SC and matrix. To tackle this problem, chemical treatment of SC or use of an alternative resin, to improve bonding should be investigated.     

Continuous resistance welding of thermoplastic composites: Modelling of heat generation and heat transfer

A process model composed of electrical and heat transfer models was developed to simulate continuous resistance welding of thermoplastic composites. Glass fabric reinforced polyphenylenesulfide welded in a lap-shear configuration with a stainless steel mesh as the heating element was considered for modelling and experimental validation of the numerical results. The welding temperatures predicted by the model showed good agreement with the experimental results. Welding input power and welding speed were found to be the two most important parameters influencing the welding temperature. The contact quality between the electrical connectors and the heating element was found to influence the distribution of the welding temperature transverse to the welding direction. Moreover, the size of the electrical connectors was found to influence the achievable welding speed and required power input for a certain welding temperature.     

A new method of reducing contact heat transfer in vacuum-screen insulation

A heat treatment method is proposed for vacuum-screen insulation that substantially reduces the contact heat transfer and halves the heat flux. The performance is illustrated on cryogenic pipelines with various forms of insulation.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 54, No. 3, pp. 446–450, March, 1988.