摘要:

AbstractCrystallization from the melt of nylon 66 in the presence of carbon fiber, aramid fiber, or nucleating agent was studied using differential scanning calorimetry (DSC) and hot stage microscopy. The use of the nucleating agent resulted in an increase in crystallization rate and a decrease of induction time under both isothermal and nonisothermal conditions. The fibers were found to behave like a giant nucleating site producing a uniform transcrystalline layer having morphology and crystallization kinetics different from those of the bulk matrix. The influence of the cooling rate on the process of nonisothermal crystallization was analyzed, and the values of activation energy, calculated from the cooling rate—crystallization temperature relationship, appeared to be higher for the nucleated and for the reinforced nylon compared with that of the neat nylon 66. This implied that the presence of fibers or nucleating agent led to the development of a more ordered structure, which required a larger amount of energy for crystallizatio

ISSN:0272-8397    

DOI:10.1002/pc.750160302

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractUnsteady two‐dimensional thermal analysis has been performed on PEEK/AS‐4 fiber thermoplastic composites. To calculate the crystallinity of the composite, a spherulite growth model was applied. A numerical analysis was carried out with variations in mold cooling rate, the prepreg lay‐up, and the composite geometry. The effect of geometry and the cooling rate is significant in the temperature profiles. The degree of crystallinity varies with the cooling rate, but the gradient of crystallinity is small, with the exception of complex geometries at fast cooling rates. The results of numerical calculations are in excellent agreement with the experiments and offer validation of the numerical formul

ISSN:0272-8397    

DOI:10.1002/pc.750160303

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractIn attempts to identify potential applications for refined commingled postconsumer plastics, a feedstock containing about 80% polyethylene (PE) and lesser amounts of poly(ethylene terephthalate) (PET), polystyrene (PS), polypropylene (PP), and poly(vinyl chloride) (PVC) was modified through functionalization with maleic anhydride in a co‐rotating intermeshing twin‐screw extruder. The modified and unmodified blends were compounded with various fillers and reinforcements such as glass fibers, mica flakes, talc, and calcium carbonate. Injection molded composites based on the modified matrix had, in general, superior mechanical and thermal properties. These findings are discussed in view of the improved adhesion resulting from reactions and/or enhanced polar interactions at phase boundaries. Several compounds prepared in this work had overall property data comparable to, or approaching those, of equivalent commercial HDPE molding compounds that are commonly used in “durable” appli

ISSN:0272-8397    

DOI:10.1002/pc.750160304

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractFatigue behavior of carbon fiber reinforced poly(etheretherketone)(PEEK) laminates was investigated. The static tensile measurement, tension‐tension fatigue loading tests, and residual tensile strength measurement of the [0/45/90/‐45]2sAS‐4/PEEK laminates were performed at various levels of stress amplitudes. The influences of stress amplitude on the fatigue life and the residual tensile strength were investigated. The experimental results for fatigue life and residual tensile strength under different stress amplitudes are analyzed by the median rank method. TheS‐Ncurves at various survival probabilities are also presented by the pooled Weibull distribution function. Furthermore, a residual strength degradation model is used to predict the residual strength for the composites subjected to a number of fatigue cycles and to simulate the effects of the stress amplitude on the fatigue life. The agreement between experiment and theory

ISSN:0272-8397    

DOI:10.1002/pc.750160305

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe Properties of three kinds of carbon fibers, which were pre‐carbonized at 500, 550, and 600°C during two‐stage continuous carbonization, were measured after being air oxidized for periods of 1 to 6 min at 550°C. The effects of precarbonization temperatures on mechanical properties, density, morphology, elemental compositions, and microstructure of the carbon fibers are discussed. The pre‐carbonization process affected strongly the surface properties and mechanical properties of the final carbon fibers, as measured after air oxidation. Carbon fibers measured one to six min after air oxidation showed a different oxidation behavior in the surface morphology for each pre‐carbonization temperature. Optimum conditions not only improved the tensile strength and modulus by over 50%, but also increased the density and oxyge

ISSN:0272-8397    

DOI:10.1002/pc.750160306

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractDielectric studies in epoxy and epoxy composites, containing different volume fractions of three different dielectric fillers, have been performed using the impedance bridge method for the high frequency region, 102to 105Hz, and the d.c. transient current method for the low frequency region, 10−4to 10−1Hz. It has been observed that, in the high frequency region, the dielectric constants of the epoxy composites increased with the addition of the dielectric filler and with the increase of the dielectric constant of the filler. The intensity of the β‐relaxation was reduced for the composites compared to an equal volume of epoxy, owing to the decrease in the concentration of the diester segments in the composites. From the low frequency data, the epoxy and epoxy composites behaved more debye‐like with increasing temperature. Also, the dielectric loss factor increased, but the thermal activation energy value to relaxation decreased two to four times in going from the unfilled to filled materials, which was thought to be attributed to Maxwell‐Wagner buildup of interfacial charges at the epoxy/fillers

ISSN:0272-8397    

DOI:10.1002/pc.750160307

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThis study deals with the degradation of mechanically‐fastened GFRP joints immersed in hot water (80°C). The material used was randomly oriented E‐glass fiber continuous strand mat with a crosslinked polyester. Three kinds of joint geometries were adopted; thickness was 3 mm, hole diameter was 6 mm, the distance from hole center to top‐edge was 18 mm (3e), and specimen widths were 18 (3w), 30 (5w), and 42 mm (7w). Failure modes of original dry specimens were a function of joint geometry, The dominant failure mode of 3w3ejoints was net‐tension, whereas 5w3eand 7w3ejoints displayed bearing failure. As degradation progressed, the dominant failure mode gradually shifted from net‐tension to bearing failure. Strength reduction was marked in 5w3eand 7w3ejoints, in which the dominant failure mode was bearing. Joint strength and failure mode were predicted from the combination of a macroscopic failure criterion and characteristic curves obtained from tensile testing of rectangular specimens with holes, bearing tests, and finite element analysis. Predictions agreed with

ISSN:0272-8397    

DOI:10.1002/pc.750160308

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractAdvanced fiber reinforced polymer composites have been increasingly used in various structural components. One of the important processes to fabricate high performance laminated composites is an autoclave assisted prepreg lay‐up. Since the quality of laminated composites is largely affected by the cure cycle, selection of the cure cycle for each application is important and must be optimized. Thus, some fundamental model of the consolidation and cure processes is necessary to properly select the suitable parameters for each application. This study applied the theory of consolidation and flow in a porous medium to provide a general model for the three‐dimensional consolidation process of the laminates with fibers reinforced in multi‐directions. Based on the model analysis, one can predict the pressure, velocity, and laminate thickness during consolidation process, which, as coupled with the curing analysis, can be used to properly select the cure cycle for applications of laminated compo

ISSN:0272-8397    

DOI:10.1002/pc.750160309

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe mechanism of fiber length degradation during twin screw extrusion compounding and methods to reduce it through process and machine design are extremely important in discontinuous fiber reinforced composites. Fiber damage along the screw and the extruder die are determined for three screw designs with different mixing sections. The pellet quality, wet‐out, and fiber dispersion in the extruded strands are compared. The fiber orientation distributions in the screw are determined to identify regions of higher fiber interaction. The fiber damage during subsequent injection molding has also been determined. The tensile, flexural, and impact properties of the tensile bars are compared. It is found that the residence time, fill‐up, and the intesity of mixing during extrusion compounding have a predominant effect on fiber length degradation. The screw designs were seen to have a greater effect on the fiber damage in the 40 wt% glass‐filled polymer than the 30 wt% glass‐filled polymer. However, the mechanical properties of the 30 wt% glass‐filled polymer showed an increasing trend compared to the 40 wt% glass filled polymer. A screw design that provides a balance of the fiber length, wet‐out, and fiber dispersion was noted to give consistent mechanical

ISSN:0272-8397    

DOI:10.1002/pc.750160310

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

ISSN:0272-8397    

DOI:10.1002/pc.750160301

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY