Sonic Modulus Research Articles

Young’s modulus measurements of magnesia–spinel composites using load–deflection curves, sonic modulus, strain gauges and Rayleigh waves

Abstract The extent of interlinking of the microcracking and a decrease in strength and modulus values were determined to be a function of both spinel particle size and volume fraction to allow calculation of thermal shock parameter, R‴. Measurements of Young’s modulus were carried out both at room temperature and after thermal shock testing by using the load–deflection curves (defined as “mechanical” modulus) and by the sonic modulus technique. The values obtained from these methods were significantly different for quenched/unquenched samples. To understand the basis for these differences, strain gauge and Rayleigh wave methods were also used to determine Young’s modulus of the composites. Modulus values obtained from these methods confirmed the differences measured, and provided a guide to the values to be used in calculating thermal shock parameters. The mechanical modulus technique was considered the most meaningful indicator of Young’s modulus for a situation in which large mechanical strains were to be applied to the materials during thermal shock.

Determination of intrinsic physical constants of poly(trimethylene terephthalate) from drawn filament

AbstractThe intrinsic lateral sonic moduli of the crystalline and amorphous regions of poly(trimethylene terephthalate) (3GT) (about 4.1504 ± 0.8396 GPa and 1.6096 ± 0.0368 GPa, respectively) were obtained from sonic moduli and crystallinities of unoriented 3GT filaments annealed under different conditions. Using the obtained intrinsic lateral sonic moduli of the crystalline and amorphous regions, the degree of orientation of the amorphous region of uniaxially drawn 3GT filaments could also be obtained from the crystallinity, sonic modulus, and the degree of crystalline orientation estimated from X‐ray azimuthal scan data. Thus, the intrinsic birefringences of the perfectly oriented crystalline and amorphous regions of the 3GT fibre (about 0.2057 ± 0.0160 and 0.2175 ± 0.0923, respectively) could be obtained from the appropriate combinations of birefringence, crystallinity, and the degree of orientation of the crystalline and amorphous regions.© 2003 Society of Chemical Industry

Structure development during dry–jet–wet spinning of acrylonitrile/vinyl acids and acrylonitrile/methyl acrylate copolymers

AbstractDry–jet–wet spinning of three copolymers, poly(acrylonitrile/methyl acrylate), poly(acrylonitrile/methacrylic acid), and poly(acrylonitrile/itaconic acid), was performed with a dimethylformamide/water (60:40 v/v) coagulation bath at different temperatures (10–40°C). The fibers were stretched to different levels (1.1–6×) in boiling water, collapsed, and annealed over a heater plate at 130°C. The effects of the polymer composition, coagulation bath temperature, and draw ratio on the cross‐sectional morphology, structure, and tensile properties are reported. The cross‐sectional shape of the gel fibers underwent a transition from a kidney shape to an oval shape, and macrovoids began to appear at higher temperatures. However, F(AN/IA) gel fibers changed from a kidney shape to an irregular shoe type with a gel network of interconnected polymer fibrils. For F(AN/MAA) gel fibers, the diameter increased from 45 to 67 μm when the coagulation bath temperature was increased from 10 to 40°C, and the denier value decreased from 17.5 to 14.3 den/filament. The strength, modulus, and elongation at break decreased with an increase in the coagulation bath temperature. For F(AN/MAA) fibers coagulated at 10°C in a spin bath, the strength increased from 0.43 to 2.213 g/den, the modulus increased from 27 to 76 g/den, and the density increased from 1.177 to 1.196 g cm−3 when the gel fibers were drawn to 6×. However, 6× drawn F(AN/MA) fibers had a higher strength (3.1 g/den) and elongation (14.6%) in a 40°C coagulation bath. F(AN/IA) fibers could be drawn only to a draw ratio of 4× instead of the 6× draw ratio for F(AN/MAA) and F(AN/MA) fibers. Therefore, the final F(AN/IA) fibers exhibited poor mechanical properties (tenacity = 0.81 g/den, modulus = 22 g/den, and elongation at break = 8%). The crystallinity did not change significantly (χc = 61–63%) with the draw ratio, but the crystal size increased from 22.9 to 43.4 Å and orientation factor from 0.41 to 0.78. The dichroic ratio, measured with Fourier transform infrared, decreased with an increase in the draw ratio, but the sonic modulus and crystalline orientation values increased with an increase in the draw ratio. Thermomechanical data show a maximum physical shrinkage of 51.7% for 6× drawn F(AN/MA) and a minimum physical shrinkage of 30.5% for 4× drawn F(AN/IA) fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 773–787, 2002

The structure and properties of cellulose fibres spun from an anisotropic phosphoric acid solution

The structure and the mechanical properties of a newly developed highmodulus/high strength cellulose fibre spun from an anisotropic solution in phosphoric acid are discussed and compared with those of existing regenerated cellulose fibres. The crystal structure of the fibre is of the cellulose II modification, and the highly oriented and crystalline fibres have an initial filament modulus of 44 GPa, a sonic modulus of 58 GPa, and a strength of 1.7 GPa. It is shown that the mechanical properties of this fibre are well described by the continuous chain model. Lateral birefringence measurements and an electron diffraction study have established the orientation of the optical axes n α and n β relative to the a and b axes in the crystal structure. Moreover, the most likely crack directions in the cellulose II structure have been identified.

Composites based on poly(ethylene terephthalate) fibers with polyaniline. I. Effect of the aniline monomer in the morphology of the PET substrate

Heat-treated PET fibers of different draw ratios (0X, 2.6X) were submitted to different conditions (time and temperature) of chemical treatments in the presence of aniline and aniline plus benzoic acid in order to verify the influence of these chemicals on their structure. Both crystalline structures of these fibers behaved similarly in some aspects to these applied chemical treatments, but differently in others. The major differences would be related to their original structures (control ones) due to the existence or not of previous orientation. The drawn fiber presented a more stable and more complex structure than that of the undrawn one. The crystalline structure of the drawn fibers changed from a two-form and more heterogeneous crystalline structure to a more homogeneous one, which is constituted of smaller and/or less perfect crystallites. The use of benzoic acid in combination with aniline seems to be more effective to plasticize both fibers, especially at higher temperatures and longer times of treatment. At these conditions, the fibers presented swelling and a more effective reduction of their glass transition temperatures (T g ). The swelling and the increase in the chain flexibility might be responsible for the formation of the more homogeneous crystalline structure of the drawn fibers. The swelling promoted not only disorientation of the amorphous regions, but disorientation of their crystalline regions as well. This phenomenon seems to be responsible for the observed decrease in the intensity of the X-ray diffractograms within a given treatment for both fibers. Sonic modulus analysis performed for the drawn fibers confirmed such data.

Nondestructive testing of polyaramide cables by longitudinal wave propagation: Study of the dynamic modulus

It has been observed that cables at different states of fatigue had their own speed of longitudinal propagation of acoustic waves (1). This speed can be measured with piezoelectric captors and is proportional to the square root of the sonic modulus. Our experiments, which have been carried out on Technora cables of diameter 2 mm, show that the modulus obtained from the wave speed has the same behavior in fatigue as the modulus obtained from tensile tests. Furthermore, our experiments also show that the residual strength in the cable is proportional to the modulus. A nondestructive control of cables can hence be made from these sonic modulus measurements.

The stress and sonic modulus versus strain curve of polymer fibres with yield

The stress vs. strain curve with yield and the sonic modulus vs. strain curve of fibres of linear polymers below the glass transition temperature are modelled by the continuous chain model in combination with a simple yield model. It is supposed that yield of polymer fibres is due to shear deformation of the domains. The yield model is based on a critical shear yield strain. A good agreement between the experimental tensile and sonic modulus vs. strain curves and the theoretical curves has been obtained for a selection of poly( p-phenylene terephthalamide) and poly(ethylene terephthalate) fibres.

Effect of Crystalline and Amorphous Structures on Biodegradability of Poly(Tetramethylene Succinate)

The effect of orientation in the amorphous and crystalline regions on the biodegradability of PTMS [poly(tetramethylene succinate)] was studied using the amorphous orientation function, birefringence, and crystallinity. The crystalline and amorphous intrinsic lateral sonic moduli, E t,c 0 and E t,am 0 , were 2.61 × 103 and 0.41 × 103 MPa, respectively. Using the data on birefringence, crystalline and amorphous orientation function (f ∈ and f am), crystallinity, and sonic modulus of the oriented PTMS fibers, the intrinsic birefringence of the crystalline (Δ c 0 ) and amorphous (Δ am 0 ) regions were evaluated to be 0.0561 and 0.0634, respectively. The biodegradabilities of oriented PTMS films were reduced as the elongation increased, i.e., the amorphous orientation increased. At low elongation (100 and 150%), however, biodegradabilities remained unchanged when the degradation test was performed in activated sludge, which was attributed to the amorphous orientation occurring even at 100% elongation, though the amorphous orientation direction was perpendicular to the fiber axis.

Mechanical and viscoelastic properties of extruded sheets from blends containing liquid crystalline copolyesters and polycarbonate

Sheets from blends containing liquid crystalline polymer (LCP) and bisphenol-A polycarbonate (PC) were prepared using a twin screw extruder at various take-up speeds. Thermal behavior, mechanical properties, and viscoelastic properties of sheets with various compositions were investigated using differential scanning calorimetry (DSC), dynamic mechanical analysis measurement (DMTA), and sonic velocity measurement. DMTA studies showed the blends to have two glass transition temperatures (Tg) corresponding to those of the PC-rich and LCP-rich phases. Blends of PC and LCP were immiscible, although their Tgs varied slightly with composition. The dynamic and sonic moduli increased with increasing LCP content owing to the high modulus of LCP. The modulus remained unchanged with increasing LCP content at low LCP wt% (<20 wt% LCP).

A six-phase model of anisotropy of polycrystalline polymers

In this paper a simple model for study of molecular orientation in polycrystalline polymers is introduced. The idea of the six-phase model resides in virtual division of the two phases (crystalline and noncrystalline) into three parts oriented in orthogonal directions. Some important parameters of the anisotropy such as the orientation function, normalized optical anisotropy parameter, birefringence and sonic modulus are discussed. It is shown that all relations usually used for description of anisotropy of polycrystalline polymers can be easily derived from the six-phase model.

Effect of γ-irradiation on the ultrasonic and structural properties of polyoxymethylene

The effect of γ-irradiation on some properties of polyoxymethylene (POM) has been investigated. A wide range of irradiation dose was covered, starting from 20 krad up to 50 Mrad. The ultrasonic pulse–echo technique, pycnometry and thermal analysis were used for the characterization of POM. The very low irradiation dose was of a potential effect on the properties of POM. A minimum in the sonic velocity, density and sonic modulus was observed at 10 Mrad. The major damage during the early stages of irradiation (<10 Mrad) occurs in the crystalline phase, and results in its degradation and fragmentation. Above 10 Mrad, the major changes are due to the restructuring of the amorphous phase, forming a less perfect crystalline structure with a relatively lower crystallite size. The melting temperature of POM was reduced as the irradiation dose increased from 0 to 50 Mrad, while the mass fraction crystallinity increased. POM undergoes the highest extent of irradiation damage at 10 Mrad.

Influence of Waste Polymer Inclusion on the Performance of Oriented Polypropylene Geotextile Tapes

Part I of this series demonstrated the effects of recycled polymer inclusion on the tensile properties of oriented polypropylene tapes. Part II describes the effects of re cycled waste on structure and morphology. Under constant conditions of tape extrusion and drawing, the IR crystallinity of orientated tape shows a U-shaped relationship with waste concentration. There is a sudden drop of crystallinity at low waste concentration, which passes through a minimum with increasing waste content, and then gradually rises to the lower crystallinity value of the tape containing 100% waste. Sonic modulus and birefringence values decrease with increasing waste concentration. These changes in tape crystallinity and orientation, along with decreasing molecular weight, explain the loss of tape tenacity owing to the introduction of waste polymer during extrusion. Improved molecular orientation is evident in the presence of additional antioxidant stabilizer, because polymer chain degradation during processing is reduced.

Weather ageing characterization of the mechanical properties of the low density polyethylene

Tensile samples of low density polyethylene (LDPE) films with different thickness and disc samples for ultrasonic measurements were outdoor exposed to weather for different ageing times before being tested. The strength parameters of the material (yield strength and sonic modulus) decrease with increasing ageing time up to 7 days, then they start to recover, whereas ductility decreases continuously with ageing time. The results are discussed in terms of oxidation and cross-linking. Below 7 days of ageing the oxidation process dominates the degradation whereas above this period the cross-linking overrides the former one.

Measurement of amorphous orientation in poly(ethylene terephthalate) fibers by X-ray diffraction and its significance

The orientation of the noncrystalline (amorphous) phase in poly(ethylene terephthalate) fibers is analyzed by separating the amorphous scattering in the wide-angle x-ray diffraction patterns into isotropic and anisotropic components. Two parameters are used to characterize the amorphous orientation—the fraction of the anisotropic component and its degree of orientation. The x-ray amorphous orientation parameters are compared with the sonic modulus and the birefringence values. Our results illustrate that the intrinsic birefringence of the amorphous phase is not “intrinsic” but depends on its density. The role of the oriented amorphous phase in determining the strength (tenacity) and the dimensional stability (shrinkage) of the fibers is discussed. We conclude that although amorphous orientation determines the shrinkage, other factors such as the connectivity between the amorphous phase and the crystalline regions play an important role in determining the tenacity of the fibers. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1363–1371, 1997

Thermal behavior, morphology, and mechanical properties of blend strands consisting of poly(ethylene telephthalate) and semiaromatic liquid crystalline polymer

Polymer blends of poly(ethylene terephthalate) (PET) and a liquid crystalline polymer (LCP) [random copolymers of the poly(ethylene telephthalate) and poly(hydroxybenzoic acid)] were prepared by using a twin-screw extruder. Strands were extruded from a capillary die. Extruded strands were stretched in an oven at 80°C. DSC and SEM were employed to investigate the structural properties of the strands. Mechanical properties of the strands were evaluated by a sonic propagation method. DSC investigation suggested that LCP phases may act as a nucleating agent of PET and the orientation-induced crystallization of PET was accelerated by the presence of LCP. An SEM micrograph shows that the LCP phases formed finely spherical domains with a diameter of 0.1-1.0 μm in the PET matrix and large parts of LCP spherical droplets were deformed to fibrils. In the case of unstretched strands, sonic moduli increased linearly with increasing LCP content, because PET was reinforced by LCP fibrils as in the case of glass fiber-reinforced PET. The degree of crystallization of PET also increased with increasing LCP contents. In the case of stretched strands, sonic moduli increased with an increasing stretching ratio due to the orientation-induced crystallization of PET. A larger increasing of the sonic modulus was shown in LCP-containing strands in the regions of a low stretching ratio (1-5), since the orientation-induced crystallization of PET was accelerated by the presence of LCP phases.

The Nature of Coupling between the Crystalline and Amorphous Phases and its Effect on the Properties of Heat-set Poly(ethylene terephthalate) Fibres

Poly(ethylenc terephthalate) (PET) fibres having a wide range of structures and morphologies were prepared by heat-setting commercial PET yarn at fixed temperatures between 100 and 255°C under two conditions, i.e. while the yarn was free to relax and when it was held taut at constant length. The structural and morphological characteristics of the crystalline and amorphous phases of the fibre were obtained by using standard methods. The sonic modulus, boiling-water shrinkage, recovery during an axial load–elongation test, and uptake of disperse dye by the fibre were determined experimentally. The dependence of these physical properties on structure is critically examined in this paper. It is shown that, in addition to the well-known structural characteristics such as the content and orientation of the amorphous phase, size and size distribution of crystallites, birefringence, etc., the nature of coupling between the crystalline and amorphous phases in the fibre, which differs significantly in the two sets ...

Molecular orientation and microstructure of roller‐drawn sheets of poly(ether ether ketone)

AbstractThe rolling and roller‐drawing of poly(ether ether ketone) (PEEK) sheets were carried out in the roller temperature range of 165‐262°C. The crystal orientation functions of the PEEK sheets were determined from the azimuthal intensity distribution of wide‐angle x‐ray diffraction, and the orientation behavior in the amorphous region was characterized by the measurements of sonic modulus and polarized fluorescence. The orientation functions increase monotonically with increasing draw ratio. The orientation function in the amorphous region is close to that of crystal orientation function of the same sample. The long period evaluated by small‐angle x‐ray scattering is almost constant over the draw ratio range studied, whereas the crystallite size along the 001 plane, D001 tends to increase with increasing draw ratio. The value of the crystallite size exceeds the product of the crystallinity and the long period. The result suggests the formation of the crystalline linkages that penetrate the periodic layers. © 1994 John Wiley &amp; Sons, Inc.

Sonic modulus in fiber-axis direction of carbon fibers 1

The sonic modulus in the fiber-axis direction was measured on tows and on carbon fiber-epoxy resin composite strands for a series of polyacrylonitrile (PAN)-based carbon fibers. It was found out that the sonic modulus of composite strands Es,c can be represented by the rule of mixture Es,c = Es,fυf + Es,m(1 - υf), where Es,f and Es,m are the sonic moduli of the fiber and the matrix, respectively, and vf is the fiber volume fraction. It follows from this result that the measurement of sonic modulus of composite strands can be used as a convenient method for determining the volume fractions of fibers in composite strands if the sonic moduli of the fiber and the matrix are known in advance. The variation of sonic moduli of carbon fibers with applied stress σ at small stress ranges can be represented as Ef = [1 - (25111/S11)σ]/S11 where S11 is the initial compliance. The factor, 2S111/S11, was found to be almost constant for a variety of PAN-based carbon fibers. The relations between the parameters representi...

Ultrasonic and thermal properties of γ‐irradiated low‐density polyethylene

AbstractThe ultrasonic pulse‐echo technique and differential thermal analysis were utilized to characterize and to monitor the effect of γ‐irradiation on the sonic modulus and the heat effect of low‐density polyethylene. The sonic wave velocity, sonic modulus, and specific gravity exhibit a minimum for samples irradiated at 10 Mrad. A minimum in the heat capacity was observed at 1 Mrad. The estimated relative change of the activation energy of ordering exhibits a minimum at 100 Mrad. Below 10 Mrad, the perturbation and the loss of the crystalline phase override the effect of radiation cross‐linking. From 10 to 100 Mrad, the effect of cross‐linking as well as that of crystallinity are prevailing. Oxidative degradation is dominating above 100 Mrad. © 1993 John Wiley &amp; Sons, Inc.

Structure and molecular orientation of high strength poly(vinyl alcohol) fibers prepared by cross-linking/wet spinning.

The structure and orientation of high strength poly (vinyl alcohol) fibers, prepared by the crosslinking/wet spinning technique (B-type fibers), were studied by wide angle X-ray diffraction, small angle X-ray scattering, sonic modulus, and shrinkage measurements and were compared with those of conventional fibers prepared by the non-crosslinking/wet spinning technique (N-type fibers). No siginificant difference was detected in the crystallite sizes and the crystal orientations between the two types of fibers. However, the amorphous orientation of the B-type fiber was higher than that of N-type fiber. The superior mechanical properties of the B-type fibers were explained with the high drawability of the preheat-treated fibers and high amorphous orientation after heat treatment.