摘要:

AbstractThermomechanical analysis was carried out for various phthalocyanine resins. The polymer based on the C‐10 diamide resin was then chosen for evaluation as a potential composite matrix material. Prepregs with Thornel 300 graphite reinforcements were successfully prepared using a hot‐melt technique. The processability of this material was studied by employing instrumental techniques including differential scanning calorimetry, thermal gravimetric analysis and dynamic dielectric analysis. A cure cycle was developed for the fabrication of angle‐ply laminate using the conventional vacuum‐bag technique in a hydraulic press. Laminate mechanical properties both in tension and in flexure were determined. The results for the C‐10/T‐300 samples were shown to be similar to those of an epoxy/graphite and a polyimide/graphite compo

ISSN:0032-3888    

DOI:10.1002/pen.760210802

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe technology of using glass fibers to increase the modulus and the strength of polymeric systems is well‐developed. Much less widely exploited has been the enhancement of properties by orienting the molecules of the polymer itself. The purpose here was to look for a synergistic combination of these two strategies: using glass fiber‐filled polystyrene and introducing molecular orientation into the polystyrene matrix. For rheological reasons it is not possible to introduce large stretch ratios in the rubbery state and thus the amount of molecular orientation that can be frozen into the quenched glassy composite is small. Even so, however, the rubbery elongation (which we associate with subsequent molecular orientation) has a very significant effect on the final (room temperature) mechanical properties. Analysis of these properties was made in terms of various theoretical models (those of Brody and Ward, Smallwood‐Guth, and Russel and Acrivos for the Young's modulus; and that of Kelly and Tyson, as modified by Lees, for the tensile strength). These comparisons showed that the brittleness of unoriented polystyrene is such that the matrix does not effectively distribute the stress along the length of the fiber and thus the benefit of the length is not realized; whereas the higher ductility of oriented polystyrene allows such transfer and a consequent improvement of prope

ISSN:0032-3888    

DOI:10.1002/pen.760210803

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe heat transfer data recently presented by Migliaresi,et al.are used as the basis for developing two models of the coupled heat transfer‐phase transition phenomena in polymeric composites containing thermally active fillers. Both models represent an extension to heat transfer of ideas which have originated in the analysis of mass transfer phenomena in polymeric materials. The second model is able to correlate all the available data within 0.5

ISSN:0032-3888    

DOI:10.1002/pen.760210804

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe interlaminar shear fatigue behavior of the sheet molding compound SMC‐R50 has been studied. A thick‐laminate, short beam shear test was employed to characterizeS‐Nbehavior for the material at 21 and 90°C. The shear modulus (Gxy) was determined at 21 and 90°C and the effect of fatigue on modulus at both test temperatures is discussed. Scanning electron microscope (SEM) and optical photomicrographs of pristine and post test specimens were studied to assess the relationship between material microstructure and the observed fatigue results for strength and modulus. The experimental evidence suggests that the fatigue life for this material is determined by a single flaw growth mechanism, rather than a global “wear out

ISSN:0032-3888    

DOI:10.1002/pen.760210805

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractAll measures of impact resistance have shortcomings. The ASTM tests, Izod, Charpy, and drop‐dart, measure impact at a single velocity. Furthermore, the Izod and Charpy tests impose an unrealistic unidimensional stress on the test specimen. Indirect gauges of impact toughness, such as the area under the tensile stress‐strain curve (tensile work), flexural modulus, or resin cracking in mandrel bend tests, are normally conducted at unrealistically low straining rates. Variable‐rate impact testers have been developed to overcome these shortcomings. In this paper, results obtained from a variable‐rate tester are compared with those from other methods for assessing composite toughness. Data are reported for flexible and brittle low profile press molding resins, tested as SMC (sheet molding compound) moldings by Izod, drop‐dart and variable‐rate impact. Indirect measures of impact resistance, mandrel bend and flexural modulus, are also discussed. The effects of resin flexibility and the composite glass content are demonstrated. The glass content affects the ultimate failure strength of the composite but not the failure of the resin matrix. The resin flexibility affects the initial stages

ISSN:0032-3888    

DOI:10.1002/pen.760210806

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe effect of moisture on the curing reaction of Hercules 3501‐6/AS graphite‐epoxy prepreg was investigated. Test samples of prepreg were aged under humid conditions, while control samples were aged under identical temperature conditions but with negligible humidity. Determinations of the amounts of moisture absorbed and desorbed fom the samples were accomplished gravimetrically. Dielectric analysis was used to monitor the relative reaction rates and overall activation energies of the prepreg after various aging periods. Changes taking place in monomer concentrations were observed using high performance liquid chromatography (HPLC). As aging continued, samples aged under humid conditions displayed, significant decrease in the overall activation energy accompanied by increased reaction rates. This change did not occur in the control samples. Samples aged in high humidity showed increased conversion of monomers to polymer when compared to dry aged samples. The aging time required before the above changes became apparent was temperature dependent; the higher the aging temperature, the sooner the changes in reactivity occur

ISSN:0032-3888    

DOI:10.1002/pen.760210807

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractA recently developed kinetic model has been applied here to describe the polyester‐styrene addition copolymerization. By assuming that the termination step is negligible and the reaction rate between inhibitor and initiator free radical is much, faster than any other reactions, the kinetic mechanism can be simplified to be expressed as a single equation. The parameters, rate constant of initiator decomposition and rate constant of propagation, are estimated from the induction time and the time to the peak exotherm of isothermal differential scanning calorimetry (DSC) curves. Temperature profiles inside plate sections of SMC parts during molding are predicted by a mathematical model in which addition polymerization is coupled with heat transfer. The predicted temperature profiles compare well with the experimental results. The model is also used to predict the cure time of different part thicknesses, mold temperature and initiator concentration. Glass fibers playa role as a heat sink as well as heat conductor during curing. Adding glass fibers to SMC not only lowered the maximum exotherm but also reduced the cure tim

ISSN:0032-3888    

DOI:10.1002/pen.760210808

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractAn analysis for the transient deflections, bending strains, and interlaminar shear stresses in a simply supported laminated composite plate subject to low velocity impact has been obtained using a series solution of the plate governing equations. Results are presented showing the effect of plate geometry and impact location on damage mode. Computed stresses and strain are compared with impact test data to verify, the analysis.

ISSN:0032-3888    

DOI:10.1002/pen.760210809

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThis paper presents a theoretical and experimental analysis of the rheological behavior of sheet molding compound (SMC). The work analyses the squeeze flow in a parallel plate plastometer of SMC discs which contain 25 percent of fiber glass by weight. This method of flow characterization gives a good insight into the basic rheological behavior of SMC for the compression molding process when producing flat parts. The theoretical analysis applies to thickened and matured SMC at room temperature. The analysis treats SMC as a viscoelastic material having an equation of state with viscous, elastic and yield elements. The time variation of compressive force when squeezing SMC discs between two parallel plates (one fixed and one mobile) has been derived from the equation of state. The values of the viscous, elastic and yield parameters were determined by using a least squares method of curve fitting to the experimental results. There are two aspects to the reported experimental work. One aspect is concerned with showing that the three element model for the equation of state provides a realistic mathematical basis for characterizing the rheological behavior of SMC at room temperature. The other shows how the parallel plate plastometer can be used to give data which characterize SMC flow behavior under conditions similar to those of the actual compression molding process.

ISSN:0032-3888    

DOI:10.1002/pen.760210810

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe development of polymer/concrete composites is directed at both improved and new construction materials by combining the ancient technology of hydraulic‐cement‐concrete with the modern technology of polymers. The need for such materials has always existed since the traditional construction material portland‐cement‐concrete (PCC) suffers the drawbacks 4 little or no resistance to chemical attack; rapid deterioration under freeze/thaw conditions due to cyclic temperature changes; low tensile, shear and bond strengths; and inherent micro‐structural menaces (voids, shrinkage‐cracks, capillaries) which, individually or in combination with each other, shorten the service life of the

ISSN:0032-3888    

DOI:10.1002/pen.760210811

出版商:Society of Plastics Engineers, Inc.    

年代:1981

数据来源: WILEY