Constitutive modeling for large deformation behavior of thermoplastic olefin

A constitutive model has been developed to capture the rate-dependent large deformation behavior of the polypropylene (PP)/elastomer/inorganic filler ternary phase thermoplastic olefin (TPO). As the TPO exhibits elastic behavior of each constituent phase during elastic deformation and shear yielding of PP matrix after linear elastic loading. The elastic modulus of the composite is predicted using micromechanics theory. The viscoplastic behavior of TPO is described by a model which includes rate and temperature dependent yield, strain softening, and strain hardening. The material properties of the model are obtained from the uniaxial tensile test and then the model is examined for its ability to predict the response in deformation. It is proved that the large deformation features of the TPO composites are well described by the constitutive model.     

On the recyclability of a cyclic thermoplastic composite material

The recyclability of a novel cyclic thermoplastic composite material has been investigated. The virgin composite was prepared by liquid molding the cyclic thermoplastic resin and a knitted glass fabric. The resultant high fiber content composite (58.7% fiber weight fraction) was recycled by grinding/compounding/injection molding process. A variety of physical and mechanical tests were then conducted on the blended cyclic composite and a baseline, commercially available short fiber reinforced thermoplastic composite. In general, the recycled cyclic composite demonstrated comparable properties to the baseline material. The only exception being the ultimate tensile elongation of the recyclate, which was almost 25% lower than that of the baseline.     

Strain stability in a material

A parameter is proposed for describing the state of a material, which is the derivative of the strains with respect to the stresses with unaltered loading conditions and changes only in the material's compliance. It is shown that this parameter is related to the rigidity of the loading system and also to the shape and size of the loaded element. The scope is considered for using this parameter to estimate the strain stability. It is found that the strain loses stability if is numerically equal to or less than the compliance of the material.Translated from Problemy Prochnosti, No. 3, pp. 74–81, March, 1994.     

Squeeze flow testing of glass mat thermoplastic material

The anisotropic flow behaviour of glass fibre/polypropylene glass mat thermoplastic (GMT) has been investigated using axisymmetric squeeze flow testing between parallel circular plates. The material has a continuous swirled fibre mat construction and is manufactured by the melt-impregnation technique. Constant plate velocity squeeze flow tests have been carried out under isothermal conditions to cover a range of strain rates. Modelling of squeeze flow behaviour has been based on two simple expressions: one assumes pure shear flow during testing, while the other assumes pure biaxial extension (plug flow). The modelling results suggest that biaxial extension dominates the isothermal squeeze flow process, with apparently negligible shear flow effects.     

Investigations on hygrothermal aging of thermoplastic polyurethane material

In this investigation, the absorption and diffusion of water in thermoplastic polyurethane (TPU) was studied. Water-sorption experiments, physical and mechanical property tests were performed after immersion in water at a set temperature of 70 °C for up to 6 months. Emphasis was given to the effect of immersion aging on thermal, mechanical and tribological properties. Fickian diffusion behaviour was found during the initial immersion time followed by saturation stage as time progressed. The use of differential scanning calorimetry (DSC) analysis showed that the glass transition temperature (Tg) was sensitive to the effect of hygrothermal aging and it decreased with increasing water uptake.More significantly, the mechanical properties in bulk material, obtained from tensile test, were affected by aging. Elastic modulus and stress at 200% of strain of the studied TPU were decreased after sufficient exposure to moisture. On the other hand, the mechanical properties of the material surface were equally investigated with the help of an abrasive wear test. A decrease in wear resistance of the aged TPU was discerned. The reversibility of mechanical and physical properties after moisture exposure was also assessed in this study. The polymer degradation was found as irreversible phenomenon.Finally, the evolution of the mechanical properties seems to be well correlated to structural modifications obtained from Fourier transform infrared spectroscopy (FTIR) characterization.     

热塑性弹性体材料的研究进展与市场前景

本文综述了热塑性弹性体 (TPE)材料的发展 ,共混型TPE的动态硫化技术及制备TPE的技术条件 ,评述并展望了其发展态势与方向     

Assessment of rheological and mechanical properties of nanostructured materials based on thermoplastic olefin blend and organoclay

This work aims to assess rheological and mechanical properties of thermoplastic olefin (TPO) nanocomposites reinforced by organo-modified montmorillonite (OMMT). In this regard, TPO/OMMT nanocomposites were produced via melt compounding and characterized in terms of OMMT content and processing parameters. The main objective of the work is to determine the optimum OMMT content and processing parameters. Both dynamic oscillatory and steady shear measurements revealed that a very good degree of OMMT dispersion occurs in the case of nanocomposite containing 3 wt.% OMMT which was also verified by X-ray diffractometry and transmission electron microscopy. Mechanical properties were studied through tensile and impact tests. It was found that as the OMMT content increases, tensile modulus and tensile strength are increased but impact strength is reduced. The optimum properties were observed at 3 wt.% OMMT which is in conformity with the rheological analysis results. As the main processing variables in melt compounding, the effect of mixing time and rotor speed on mechanical properties of TPO nanocomposites were studied and correlated to their rheological properties. It was concluded that using an intermediate mixing time and rotor speed would be more appropriate to achieve desirable mechanical properties.     

Investigation of a novel poly (lactic acid) porous material toughened by thermoplastic polyurethane

Journal of Materials Science - Poly (lactic acid)/thermoplastic polyurethane (PLA/TPU) ductile fibrous porous material was obtained by electrospinning, which has better mechanical properties than...     

Possibility of closed loop material recycling for fiber reinforced thermoplastic composites

It becomes significantly important to preserve ecological balance of the earth and protect the environment from getting worse. One of the urgent issues to be tackled will be to develop and establish recycling technology for polymeric composite materials. The expression of recycling technology in this case is that after the life of industrial products of fiber reinforced thermoplastic (FRTP) is completed, instead of being thrown away as wastes, they are reused as a raw material for new applications. An additional goal is that of saving valuable resources and not consuming further energy. This paper deals with a possibility of closed-loop recycling technologies for FRTP. The key factor is the fiber length which is expected to reduce in each recycling step. Materials tested here are continuous FRTPs, long FRTPs, short FRTPs, and powder reinforced plastics. The effect of fiber length on the reinforcing mechanism is first examined. The correlation between outdoor exposure test and accelerated weathering test is the second subject to covered. The third subject is to make clear the influence of crushing and heat history which are inevitable during each recycling stage. Throughout the above investigation, the concept of closed-loop recycling technologies has been established, although it is still in a preliminary stage.Abbreviations FRTP fiber reinforced thermoplastic - C-, L-, S-, P-FRTP continuous-, long-, short-FRTP, powder-RTP - FRP fiber reinforced thermosetting plastic - UD unidirectional - PP polypropylene - CF carbon fiber - GF glass fiber - V _f volume fraction of fiber     

Green thermoplastic elastomer based on polycaprolactone/epoxidized natural rubber blend as a heat shrinkable material

Green thermoplastic elastomer based on polycaprolactone and epoxidized natural rubber blend was prepared by melt mixing process. Effect of crosslinking by dicumyl peroxide and rubber content on heat shrinkable behavior of the blends was studied. It was found that the crosslinking enhances the heat shrinkability of the blend, and in the case of uncrosslinked blends, the blend containing higher amount of rubber showed greater heat shrinkability.     

Strain characterization of anisotropic material by thick ring pressure test

A pressure test of a thick ring of anisotropic material such as unidirectional carbon fibre-reinforced epoxy composite can give accurate values for both the axial and transverse Young's moduli, and adequate values for both of the Poisson's ratios. The test is easily and quickly performed, and requires only the measurement of pressure, deflection of the outside circumference, and deflection of the radial wall thickness. The test and its theory are described. Sample results are given with estimates of their accuracy.     

High Performance Flexible Strain Sensors Based On Silver Nanowires/thermoplastic Polyurethane Composites for Wearable Devices

Applied Composite Materials - Flexible strain sensors have attracted numerous attentions due to their application in wearable devices. However, it is still a significant challenge to fabricate...     

Fabrication characteristics of a carbon fibre-reinforced thermoplastic resin

Investigations are described which were designed to identify the origin of the phenomenon of kinking in carbon fibre-reinforced polyetheretherketone (PEEK). Preliminary observations upon the production and subsequent behaviour of specimens of the pure matrix resin led to the recognition of the inducement and subsequent relaxation of preferred molecular orientations, which could result from changes of temperature and pressure. These observations were followed by a series of experiments upon commercial prepreg, from which some of the critical parameters in kink formation were identified.     

Tribophysical and tribochemical effects of a thermoplastic polyimide

The sliding friction and wear characteristics of a thermoplastic polyimide (PI) were investigated under different PV conditions using a pin-on-disc wear tester. The tribological characteristics of the PI were divided into three wear regions on the basis of the wear degree (slight wear, medium wear and severe wear). The friction coefficient of the PI in slight wear was stable. In the medium wear and severe regions, the friction coefficients of the Pl varied over a wide range, and was unstable. The reason for the variations of friction and wear in the different wear regions was attributed to the rising of PI surface temperature, which led to the variations of the physical state of PI friction surface layer. XPS analysis indicated that carbonation occurred on the friction surface during sliding. It was proved that the reaction product may reduce the friction coefficient.     

Creep crack growth in joints of a thermoplastic

An investigation of creep crack growth in butt heat fusion joints in a high density polyethylene (HDPE) is performed to quantify their life expectancy. Three point bend specimens containing a centrally located notched joint are used in creep crack growth tests at ambient and elevated temperatures. A quasi-nonlinear viscoelastic fracture mechanics model is used to deduce the crack growth histories from the measured load-point displacement histories. The initiation time for crack growth and the rate of crack growth are correlated with the stress intensity factor for combinations of initial crack lengths, applied loads and test temperatures. The elevated temperature data are shifted bidirectionally, utilizing shift functions derived from stress relaxation tests, to develop master curves for the initiation time and rate of crack growth. These master curves are used to predict the life of a girth joint containing an initial circumferential surface crack extending through 10 percent of the thickness of a pressurized pipe.     

Fabrication of a submicrometer crystalline structure by thermoplastic holography

We report what we believe to be a novel method for fabrication of permanent submicrometer periodic structures by interference laser fields. The new method is holographic lithography combined with laser-induced thermoplastification. The crystalline structures that result from this new method not only can be maintained permanently after the optical field is evacuated but also can be rewritten by exposure of an inteference laser field for the second time. The process of fabrication is rapid, convenient, and effective.     

热塑性树脂基复合材料焊接研究

综述了国内外正在广泛研究的4种焊接方法:电阻焊植入焊,超声焊,感应焊和线性振动焊,介绍了这4种方法的基本原理,并分析了焊接过程中应注意的关键问题,对比了这些方法的优、缺点,并展望了当前的研究动向.