摘要:

AbstractComparative single fiber fragmentation test measurements are used to charcterize cynate and epoxy resin interface load transfer with high modulus (HMS4) and high strength (AS4) carbon fibers. The HMS4 fiber forms a weak interface with a fiber controlled failure mode, and the AS4 fiber forms a strong interface with the resin properties, apparently determining the level of load transfer. The resin properties examined are critical surface energy for wetting, cure shrinkage, thermal shrinkage, and mechanical modulus and strength. The cynate and epoxy resins display no significant difference in critical surface energy. Cure shrinkage has a negligible effect on load transfer. The compressive force from thermal shrinkage is significant, but the largerTgto testing temperature range of the cyanate resin is offset by the larger thermal expansion coefficient of the epoxy, resulting in a near equal compressive force for the two resins. There is little difference in modulus between the two resins but a significant difference in shear strength. This difference is reflected in the larger load transfer measurement for the cyanate resin. A comparison of simple one‐dimensional elastic and plastic models for the fiber fragmentation experiment resulted in better conformity with the plastic model. This would indicate that interfacial failure occurs by plastic deformation of the resin for the systems of this stud

ISSN:0272-8397    

DOI:10.1002/pc.750150602

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effect of die design on the flow characteristics of compression molded three‐layer long glass fiber reinforced polypropylene composite, known as “stampable sheet,” was investigated. The flow behavior of each layer was observed by optical and soft X‐ray photographs. The fiber flow length into the rib part was measured by an image processing system. The results showed that during compression resin exudation occurred and that this depended on the die's rib width. Thus, the larger the rib width, the lower the amount of resin exuded. Resin exudation was found to occur earlier in a die with zero fillet radius. The fiber flow length into the rib part was enhanced by using a die with a large fillet radius. The results were confirmed by a short‐shot molding process. In this process, the stamping operation was stopped short of making a complete part.A finite element method was used to study the flow process. The results agree with the experimental results confirmed by short‐s

ISSN:0272-8397    

DOI:10.1002/pc.750150603

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY

摘要:

AbstractA continuous stabilization and two‐stage carbonization process was used to prepare polyacrylonitrile (PAN)‐based carbon fibers, The effect of pre‐carbonization (300 to 550°C) on the final properties and microstructure of carbon fibers was measured. Experimental results using an X‐ray diffractometer indicated the presence of a less ordered structure at 2Θ from 5 to 18° in the pre‐carbonized fibers and the final carbon fibers. This study found that the pre‐carbonization process strongly affects the microstructure of the resulting carbon fibers. The results also showed that a suitable pre‐carbonization was very conducive to improvement in tensile strength or in Young's modulus of the final carbon fibers. When the final carbon fiber was pre‐carbonized at 300 and 550°C, respectively, these fibers had a higher tensile strength and higher Young's modulus than carbon fibers pre‐carbonize

ISSN:0272-8397    

DOI:10.1002/pc.750150604

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY

摘要:

AbstractThis study deals with the hydrothermal effects on mechanically fastened glass fiber mat/polypropylene composite joints with different joint geometry. Three kinds of joint geometries were adopted; hole diameter was 6 mm, the length from top edge to the hole center was 18 mm (3e) and the specimen width was 12 (2w), 18 (3w), and 30 mm (5w). The joints were immersed in hot water at 60 and 80°C. The effect of water temperature on the failure load appeared clearly in 2w3ejoints. The higher water temperature induced more strength reduction. The dominant failure mode changed from the net‐tension to the bearing for the original dry joints for wider specimens. The failure mode changed from multiple to net‐tension only for 3w3ejoints, because of a remarkable tensile strength reduction. The failure strength and the failure mode were predicted by the macroscopic failure criterion, and the characteristic experimental curves, and the FEM analysis. The predicted results agreed with experi

ISSN:0272-8397    

DOI:10.1002/pc.750150605

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY

摘要:

AbstractIn recent years the emphasis on the development of fiber reinforced plastics has experienced an unprecedented expansion. One of the most commonly used methods in manufacturing of plastic products is injection molding. In this work we are using a Generalized Eulerian Lagrangian (GEL) formulation to study the unsteady flow of dilute fiber suspensions in injection molding. This formulation combines the advantages of both formulations: in the same flow problem but different regions the GEL formulation allows the selective application of an Eulerian, Lagrangian or a mixture of the two formulations. The suspending fluid is considered to be Newtonian and the contribution of the fibers to the local stress tensor is obtained using a volume averaging theory. The fiber distribution tensor is expressed in terms of a second order tensor with a quadratic closure approximation. Results are shown and discussed for the filling of a cavity from a single gate under different process conditions fibers aspect ratio and content.

ISSN:0272-8397    

DOI:10.1002/pc.750150606

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY

摘要:

AbstractThe rheology of two polyamide 6.6 systems filled with long glass fibers, as well as at of a three‐phase polyamide 6.6‐glass fiber‐gas bubble system, was studied using capillary rheometry, To investigate the influence of fiber concentration, the shear and extensional viscosities were determined for both 30 and 40 vol% fiber filled suspensions as well as for the base polymer. Comparison revealed a modest increase in both the shear and extensional viscosities with increased fiber fraction. The shear viscosities, ηs, of both suspensions are shown to be close to one order of magnitude greater than the base matrix fluid viscosity, η. However, the extensional viscosities, ηE, of the suspensions are determined to be approximately four orders of magnitude greater than the shear viscosity of the matrix fluid for strain rates from 100s−1to 102s−1. The addition of a gas bubble phase to the neat polymer and polymer‐fiber suspensions was accomplished through the decomposition of various percentages of an azodicarbonamide blowing agent. The presence gas bubbles resulted in reduced shear and extensional viscosities for both the neat and fiber‐filled polyamide with greater reductions observed for the neat polyamide. Greater viscosity reductions were observed as the blowing agent centrati

ISSN:0272-8397    

DOI:10.1002/pc.750150607

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY

摘要:

AbstractA study of the use of thermoplastic powder coated towpregs in filament winding was conducted. A suitable technique for manufacturing parts with adequate on‐line consolidation was identified through an experimental investigation that compared several techniques. This process utilized a single compaction roller on‐line consolidation head with hot air guns to obtain consolidation at the lay‐down point on the mandrel. The addition of a heated pultrusion die between the creel system and the filament winder was found to produce the best process. Nylon 11/E‐glass towpreg was used in this study. The effect of winding speed and compaction force on the quality of the resulting parts was determined in order to optimize the process. Only the speed was found to have a significant effect, with better quality parts being made at higher speed. Observations were also made on parts manufactured with polypropylene and E‐glass towpreg, as well as on parts wound with helical

ISSN:0272-8397    

DOI:10.1002/pc.750150608

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY

摘要:

AbstractMechanical spectrometry was performed on polystyrene/glass bead and poly (styrene‐co‐methacrylic acid)/glass bead composites to test for the influence of the interphase on molecular mobility. To quantify these motion changes, a physical model was developed to predict the deformation of amorphous materials nearTg. Before applying this model, the dynamic mechanical behavior of the two phases (matrix and inclusions) must be separated to remove the reinforcement effect of the fillers and to keep only the physical crosslinking effect of the amorphous phase by the inclusions. It was shown that (i) the fillers can induce the nation of specific interactions, which act as physical ties, reducing molecular mobility and that (ii) the decrease in molecular motion with increasing filler content is enhanced for fillers coated by a silane coupling ag

ISSN:0272-8397    

DOI:10.1002/pc.750150609

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY

摘要:

AbstractThe resin film infusion process (RFIP), which is similar to resin transfer molding (RTM), was applied to investigate the possibility of manufacturing high performance stitched composites. With the objective of understanding the resin flow mechanisms and void formation in stitched fibrous perform, two recent technological developments in homogeneous tough resin and bendable stitching fibers were incorporated in producing stituched composites with RFIP. These included new lightly crosslinked thermosets (LXT) that were phenolic or amine based. Second, bendable carbon stitching reinforcement (T‐900) was utilized as a stitching fiber. Flow characteristics were inferred by ultrasonic C‐scan analysis of cured panels. Microscopic studies indicated that voids were distrubuted along the stitching fiber because of low consolidation pressure in the resin‐rich area (stitching fiber region) where the fiber volume content was lower. In contrast to stitched composites, non‐sitiched composites contained lower void content and irregular void distribution because of uniform fiber compaction. Microscopic studies of partially resin infused quasi‐istropic stitched composites demonstrated that the resin flows along the stitching fiber region and then infuses into the fibrous preform. These infusion phebnomena were the result of anistropic permeability in the preform. Consequently, anisotropic resin flow in the stitched fibrous preform was found to be related to the heterogenous textile structure caused by the stitchin

ISSN:0272-8397    

DOI:10.1002/pc.750150610

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY

摘要:

AbstractA series of all‐hydrocarbon resins were synthesized by reacting cyclopentadiene allyl chloride, propargyl chloride, or a mixture of allyl chloride and propargyl ide, under phase transfer conditions. Phase transfer reactions with and without added solvents, and with either quaternary ammonium or crown ether catalysts, yielded similar products consisting of a mixture of 1,1‐disubstituted cyclopentadiene (minor amount) and 2‐3 isomers each of tri‐, tetra‐, penta‐, and hexa‐substituted derivatives. No further reaction of each these components possible. The overall substitution pattern varied little with changes in reaction conditions although limiting the allyl chloride content led to still reactive, partially substituted products. Incorporation of all‐propargyl and high propargyl‐to‐allyl mixed functionalities on cyclopentadiene yielded products whose stability was very hindering their thorough characterization. Preliminary evaluation was there‐carried out for mixed resins with lower propargyl functionality. The allyl substituted resin (allylated cyclopentadiene, ACP) underwent thermal cure lout initiator at around 200°C while allyl/propargyl substituted resin (7:1 ratio, APCP) showed a faster, lower temperature cure at around 120°C. Cationic cure of ACP was also initiated by a novel sulfonium salt at around 100°C. Neat resin when cured at 200°C gave material with a flexural storage modulus 2 of about 300 MPa. Further cure at 250°C raised the modulus to 1.2 GPa. resin gave composites with excellent properties when used with glass and on fibers. Flexural modulus values (by DMA) of ∼ 66 GPa were obtained for ACP/carbon fiber composites compared with 42 GPa for epoxy/carbon composites made in our laboratories using commercially available materials. The modulus values at 300°C dropped to 10% of the room temperature value for the epoxy composites, while the ACP/carbon composite maintained 60% of its room temperature value at 300°C. When brought back to ambient temperature, the modulus of latter sample had increased to 80 GPa and that of the epoxy composite dropped to 23 GPa. Glass fiber ACP composites performed similar to an epoxy composite up to 200°C but maintained properties up to 300°C while those of the epoxy were drastically reduced. TGA analysis of both cured ACP resin and its composites showed decomposition beginning at 375°C. Three‐point‐bending tests indicated very high modulus with brittle failure for ACP composites. Scanning electron micrographs showed moderate bonding of the new resin to both carbon glass fiber surfaces. This new class of thermosetting resins offers excellent potential for application in low‐cost glass and carbon composites wi

ISSN:0272-8397    

DOI:10.1002/pc.750150611

出版商:Society of Plastics Engineers    

年代:1994

数据来源: WILEY