摘要:

AbstractAn investigation was conducted to evaluate the validity of various test methods in the dtermination of in‐plane shear moduli of semicrystalline, poly(phenylene sulfide) (PPS) thermoplastic composites. Materials studied included composites based on an orginal, non‐optimized composite grade of PPS reinforced with carbon and glass fibers, and another based on the new improved, high‐ductility, rapid crystallizing, composite grade of PPS along with optimally sized glass fiber reinforcement. Specimens were prepared in a matched die mold, either as‐molded or annealed. It was found that shear test methods, such as ±45° in plane, Iosipescu, and 45° pff‐axis tension, are validfor shear modulus measurements of PPS composites if the material has no internal stress cracks. For example, there was no significant difference for in‐plane shear moduli determined from these three shear testsw for the improved, thoughened PPS composites. This was attributed to the thoughness and fast crystallization of the PPS composites. This was attributed to the thoughness and fast crystallization of the PPS matrix resin, and the strong fiber/maxtrix interface, however, the ±45° in‐place shear test should be used with caution for certain thermoplastic composites,. Becuase of the ±45° lay‐up, the annealed[±45]2soriginal PPS composite la, omates siffered jogj resodia; stresses and were observed to have stress‐related cracks. Consequently, the measured shear moduli are lower than the true values. Since we have demostrated that some shear tests amy not be appropriate for modulus measurements of certain composites, it is important to choose the proper test method for the shear characterization of

ISSN:0272-8397    

DOI:10.1002/pc.750150102

出版商:Society of Plastics Engineers, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractIn the case of total hip joint replacement, it has been shown that matching of femur and implant stiffness would positively decrease the chances of resorption of bone and clinical failure of the procedure. Short fiber composites (SFC) which are biocompatible can offer high strength with stiffness comparable to that of natural bone and hence are an excellent candidate to replace metal alloys used in orthopedic implants. In this work a computational process simulation is presented to investigate the possibility of making an artifical hip implant which is most biocompatible. This simulation computes three dimensional flow induced fiber orientation in manufacturing of an SFC hip implant, estimates its mechanical properties, and predicts its “in vivo” response. This is done using a model 3‐D geometry representing implanted femur. The potential use of such an approach is demostrated by comparing principal stresses at the interface of the bone and the implant for metallic and SFC implant which is manufactured using a variety of by proper selection of material and process variables one can potentially create implants which are most biocompa

ISSN:0272-8397    

DOI:10.1002/pc.750150103

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY

摘要:

AbstractCross‐ply tapered/stepped laminates with taper angles of 1 and 2° between the top and bottom surfaces were fabricated using T300/943 graphite/epoxy by compression molding. Ply terminations were done internally within the laminate and externally on the surface of the laminate at various cross‐sections in order to obtain the taper. Equivalent cross‐ply specimens with internal and external ply terminations, respectively, were tested in three point bending. The bending stiffness of the equivalent corss‐ply are nearly equal, while the failure modes are significantly different. The tapered laminates with internal ply terminations failed due to a series of delaminations originating at the step corners of the 0° plies. Macroscopically, the specimens with internal ply term nations failed by tensile fracture of the outer plies at relatively hig

ISSN:0272-8397    

DOI:10.1002/pc.750150104

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY

摘要:

AbstractThe influence of different process variables on the void content in resin transfer modling (RTM) has been investigated experimentally. The moldings were made in a flat mold filled by a parallel flow from one edge of the laminate to the other. The viods were found concentrated in a narrow region close to the ventilation side of the laminate. The void volume fraction in this region was almost constant and dropped over a short distance to basically no voids in the rest of the laminate. Micrographs from cross sections in different directions revealed that the voids were of two different types, long cylinderical bubbles inside the fiber bundles. An efficient way of reducing the void content was to use vacuum assistance during mold filling. This technique was benefical both for the magnitude of the void content and for the extent of the void region. The void content with the highest level of vacuum assistance (≈︁ 1 kPa absolute pressure), was practically negligible. Strong indications for void generation by mechanical entrapment at the flow front was found. The lowering of the void content with vacuum assistance can be interpreted as aresult of compression of voids when the vacuum is released and a higher mobility of voids created at a lower press

ISSN:0272-8397    

DOI:10.1002/pc.750150105

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY

摘要:

AbstractProcessing parameters for composites are predicted by new models which are based on the microstructure of the composite. Three types of termoplastic prepregs are considered, ICI tape, BASE commingled two, and CCMI powder coated tow. The permeability of the composites depends on their fiber distribution. The elastic behavior of the fiber network compression depends on the fiber oreientation. These two are integrated to predict the processing parameters.

ISSN:0272-8397    

DOI:10.1002/pc.750150106

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY

摘要:

AbstractThe permeability of termoplastic composites and the elastic behavior of their fiber networks were measured during compression molding. As these processing parameters depend on the microstructure of the composite, experiments were performed to determine them for tape prepreg, commingled two repreg, and powder‐coated tow prepreg. The experimental results agree closely when compared to the theoretical prediction

ISSN:0272-8397    

DOI:10.1002/pc.750150107

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY

摘要:

AbstractQuantitative digital image processing has been used to analyze unidirectional thermoplastic composites. The fiber volume fraction is determined by the template matching method and compared with the conventional thresholding method. A combination of skeleton and edge cutting is used to obtain the centers of the fibred in the image. The Voronoi distances are calculated from the result. The Hough transform is applied to the fiber orientation in conjunction with thresholding by the line length in the image. To describe the fiber orientation, characteristic function are defined in the width and thickness directions, which allow a much more accurate and effective description of the fiber distribution and orientation than other methods. Advantages of the template method are that similar results to the threshold method can be obtained as thresholding with a lower magnifications, resulting in an improved statistical sample with a reduced number of photomicro‐graph

ISSN:0272-8397    

DOI:10.1002/pc.750150108

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY

摘要:

AbstractThe on‐line consolidation process, using a single roller, in thermoplastic filament winding (tape laying) has been investigated. A one‐dimensional, semi‐empirical, on‐line consolidation process model is proposed that describes the deformation and flow phenomena. The model is used to predict the applied load necessary to achieve a desired fiber volume content of filament wound thermoplastic composite rings consolidated at various process conditions. Composite rings are fabricated from 50 layers of 12K carbon fiber tow APC‐2 tape (6 mm wide) on a 178 mm diameter mandrel. It was found that the winding speed had statistically significant effects on the void content, the fiber volume fraction, and the final thickness; whereas the applied load had a statistically significant effect on the final thickness. These results show the effect of shear thinning on the viscoelastic response of the material, facilitating faster processing speeds. The results of the experiments compared well to the consolidation model's pr

ISSN:0272-8397    

DOI:10.1002/pc.750150109

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY

摘要:

AbstractInjection molded short Kevlar (DuPont) fiber/nylon‐6,6 composites have been studied. Fiber length and length distribution were measured as a function of processing variables. Critical fiber length was measured by an embedded single‐fiber method. Tensile modulus of the molded composites was predicted by an adapted classical lamination analogy. Fiber and matrix orientation factors, derived from X‐ray diffraction, were introduced to modify Kelly Tyson equation to estimate the composite tensile strength. It has been found that fiber length is dramatically shortened by the injection molding process, and is affected by processing conditions. Predictions gave reasonable agreement with data for tensile modulus and str

ISSN:0272-8397    

DOI:10.1002/pc.750150110

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY

摘要:

AbstractFour types of random‐in‐plane short fiber reinforced polymer composites were manufactured by the prepreg route using carbon or glass fiber tissue and 913 or 924 epoxy resin. The in‐plane Young's modules and in‐plane shear modulus of the composites were measured over the temperature range − 100 to + 200°C by dynamic mechanical analysis using three point bend and rectangular torsion testing geometries. Theoretical predictions of the elastic properties of the composites were determined over the same temperature range and compared with the experiment. Of particular interest was the use of the “S mixing rule” of McGee and McCullough to determine a single theoretical estimate for the composite elastic properties. Excellent agreement between experiment and theory was found for the four composites over the majority of the measured tem

ISSN:0272-8397    

DOI:10.1002/pc.750150111

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY