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  • 1
    Digitale Medien
    Digitale Medien
    Batch chemical process quality control applied to curing of composite materials (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2535-2545 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Model predictive control is used extensively to control continuous-process systems. Application of a shrinking horizon model predictive control strategy is used to predict and control the end product quality of composite laminates produced by batch autoclave curing. The main contribution is the demonstration, using a laboratory-scale autoclave, of the feasibility and advantages of a control strategy that adjusts the batch recipe on-line to correct for unmeasured disturbance: entering the process. Readily available, on-line secondary measurements are used in conjunction with the process model to predict (and hence control) quality-related end product properties. On-line monitoring is also used to monitor the process even after the possibility of on-line correction has passed. The results show that this approach significantly reduces end product quality variance.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690431015
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  • 2
    Digitale Medien
    Digitale Medien
    Consolidation and self-bonding in poly(ether ether ketone) (PEEK) (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 1435-1454 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The effects of processing variables (time, temperature, and pressure) on the strength development during self-bonding of amorphous PEEK films were studied using a modified single lap-shear test. It was shown that the self-bonding strength developed isothermally at different bonding temperatures exhibits a linear response with the bonding time raised to the 1/4 power in agreement with Wool's theory. DSC measurement of the crystallinity produced at different bonding conditions demonstrated that even though PEEK specimens contain the same amount of crystallinity, the resultant self-bonding strength is sensitively dependent on bonding history. C-mode scanning acoustic microscopy (C-SAM) was applied to define the effect of the processing variables on wetting of the bonding area during the bonding process. It was shown that, above a threshold pressure (〈 17 psi), the degree of wetting depends weakly on time, but not on temperature. SEM analysis revealed that amorphous PEEK films are self-bonded by crystalline growth after diffusion and entanglement of the polymer chains across the interface. The crystalline growth rate across the interface is much higher at higher temperatures, leading to a higher self-bonding strength. The shear fracture surface observations also support the above result. The PEEK specimens showing the higher self-bonding strengths exhibit much denser striations and deeper dimplelike ductile patterns in the fracture surface, arising from much more crystalline growth across the interface. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1995.070561106
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  • 3
    Digitale Medien
    Digitale Medien
    Growth, morphology, and reinforcement potential of low molecular weight crystals in amorphous polymeric matrices (1968)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 12 (1968), S. 1151-1165 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The technique of in situ crystallization of low molecular weight organic compounds from amorphous polymers was evaluated as a method of fabricating composite materials. Two workable systems, styrene-acrylonitrile copolymer (SAN)-acetanilide and SAN-anthracene, were found and their phase diagrams determined. In both systems kinetic studies revealed that the maximum crystallization rate takes place at large degrees of supercooling and that below these temperatures the mechanism is diffusion-controlled. The temperature-dependent crystal morphologies were characterized with electron microscopy, which showed three distinctly different morphologies for both systems. From dynamic mechanical measurements, it appears that the elastic moduli of organic crystals are about the same as those of organic polymers in the glassy state, and that relatively little reinforcement took place under the particular crystallization conditions employed.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1968.070120514
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  • 4
    Digitale Medien
    Digitale Medien
    The devolatilization of polyimide fiber composites: Model and experimental verification (1994)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 15 (1994), S. 184-196 
    Details
    ISSN: 0272-8397
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: A one-dimensional devolatilization model is developed for autoclave processing of themroplastic polyimide, graphite-reinforced, composites. The model rests on the assumption that continous gas passages are formed during processing due to partical crystallization of the polymer in the course of polymerization. Both DSC and optica microscopy indicate that crystallinity develops in the Avimid-III polyimide resin during polymerization, which in turn facilitates formation of cracks. These cracks heal upon removal of volatiles and polymer melting. Model-Calculated temperature profiles in the laminate during polymerization, and the predicted removal rates of volatile species (water, ethanol, NMP) are compared to experimental miniautoclave data for the DuPont Avimid K-III/IM6 system. Good agreement is obtained when the volumetric mass transfer coefficient required by the model is assumed to vary proportionally to the inverse of the changing resin viscosity. The model allows the investigation of desired cure cycle parameters for different laminate thicknesses.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pc.750150304
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  • 5
    Digitale Medien
    Digitale Medien
    Melting of homopolymers under pressure (1965)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A: General Papers 3 (1965), S. 2827-2841 
    Details
    ISSN: 0449-2951
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The effect of pressure on the melting of polyethylene, polypropylene, poly(ethylene oxide), and poly-3,3-bischloromethyloxacyclobutane (Penton), has been studied up to 3000 atm. The melting temperature-pressure curves for all polymers studied rose indefinitely with pressure, thus behaving in a manner similar to that previously reported for long-chain hydrocarbons. For polyethylene, analysis of the total entropy change on melting, in terms of changes in configurational and volume entropies showed that the percentage of the total entropy change due to change in configurational entropy increased rapidly with pressure, attaining a value of 90% at 3000 atm. The changes in the configurational entropies of melting for polypropylene, poly(ethylene oxide), and Penton were subsequently shown to be lower than that of polyethylene suggesting more melt order. This could arise from helical conformations in the melt for polypropylene and polyethylene oxide and from a stabilized planar zigzag conformation in the Penton melt. A pronounced broadening of the melting range with pressure was attributed to pressuresensitive transitions which are known to occur near the melting temperature and also to the effect of molecular weight distribution.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1965.100030810
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