摘要:

AbstractThe design of moding tool and molding cycle for sheet molding compounds (SMC) is often expensive and time consuming. Computer simulation of the compression molding proces is a desirable approach to reduce experimental prototypes. The focus of this work is to develop an automatic optimization scheme utilizing an earlier developed SMC plrocess simulation program which is capable of simulating material flow, heat trensfer, and curing. The proposed scheme reduces computing time by using approximate responses, instead of actual simulated responses, to perform the optimization. The automated optimization package minimizes user intervention during optimal design by creating an automatic link between the optimization and simulation routines. A 2‐level factorial design combined with regression analysis is adopted to gather and analyze computed information, and to serve as the approximation formula. Two examples are presented to test the applicability of the optimization schem

ISSN:0272-8397    

DOI:10.1002/pc.750150502

出版商:Society of Plastics Engineers, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe results of studies on bending properties of three‐layer long fiber polypropylene composites are presented. Thirteen samples with glass fibers of various lengths (i.e., 13, 25, 50 mm and continuous fiber length) in the laminates were prepared by stamping. Bending properties of shorter lengths exhibited a large scatter. On substitution of the middle layer with a continuous glass fiber the scatter was reduced. These results have been explained on the basis of flow models and X‐ray shadowgraphs, which showed that both slippage flow and orientation of the glass fiber during stamping are the major phenomena responsible for the scat

ISSN:0272-8397    

DOI:10.1002/pc.750150503

出版商:Society of Plastics Engineers, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractLiquid molding processes including resin transfer molding (RTM) and structural reaction injection molding (SRIM) continue to attract attention due to their potential for high volume manufacture. This paper examines and compares the pressuare and temperature histories observed in mold cavities during impregnation, heating, and polymerization for both RTM and SRIM using polyester, vinyl ester, and polyurethane resins in combination with continuous strand mats. Experimental results are related to thermal, chemical and rheological effects. Factors which influence materials behavior and process control and the implications for mold design are discussed.

ISSN:0272-8397    

DOI:10.1002/pc.750150504

出版商:Society of Plastics Engineers, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractBlends of poly(butylene terephthalate) and high density polyethylene at a ratio of 80:20 wt% were reinforced with short glass fibers varying from 10 to 30 wt% to enhance mechanical properties. Considerable fiber damage occurred during injection molding, reducing the number average fiber length from the starting value of 4.5 mm to<1 mm. This value decreased with increasing fiber content, which is also responsible for lowering the reinforcement efficiency. The variation in mechanical properties has been explained on the basis of fiber concertration. The effect of an ionomer, which was used to compatibilize the blends, on properties of corresponding composites has also been studied.

ISSN:0272-8397    

DOI:10.1002/pc.750150505

出版商:Society of Plastics Engineers, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractLarge macroscopic‐scale variations in the tensile moduli and tensile strengths are charcteristic of random glass mat composites (GMT). The large‐scale, point‐to‐point variations in the local stiffness is characterized by a probability density function that can be used to predict the stiffness of parts only in a statistical sense. Weibull statistics widely used for modeling the scatter in the strength of brittle materials cannot be applied to the large variations in the strength of GMTs: The macroscopic stress field in brittle materials is assumed to be deterministic, while the stress field in GMTs varies randomly on a macroscopic scale. A statistical approach for characterizing the strength of GMTs is developed by combining an empirically established strength‐modulus correlation with the statistical characterization of the tensil

ISSN:0272-8397    

DOI:10.1002/pc.750150506

出版商:Society of Plastics Engineers, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractComposites based on tetrafluoroethylene‐ethylene copolymers with graphitized polyacrylonitrile fibers were developed. The effect of the fiber length and concentration on the properties of the compositions was studied. Thermoactivation of the fibers was carried out and its influence on the properties of the tetrafluorethylene‐ethylene compositions was studied. Graphitized fibers possessing the higest content of oxygen‐containing functional groups thermoacttivated at 1073 K for 30 min exerted the highest reinforcing effec (∼40%). The relation between fibers finished with γ‐aminopropltriethoxysilance and theproperties of the compositions obtained was also studied. A synergetic effect on the compositions mechanical and thermal properties was observed for the modified carbon fibers, whereas the other properties remained almost the same. The additional reinforcement of the carbon compositions modified with fiber monocrystals ofalkali titanates in concentrattions from 0.5 to 5.0 Wt% strengthens the tetrafluoroethylene‐ethylene polymer matrix by increasing the dynamic modulus, hardness, and thermoresistance of the

ISSN:0272-8397    

DOI:10.1002/pc.750150507

出版商:Society of Plastics Engineers, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractProcessing of fiber compounds in single‐screw plasticating units can cause fiber fracture. Attempts have been made to obtain large residual fiber length in finished components. Therefore, pultrusion compounded materials for extrusion and injection molding have been developed. Pellets chopped from pultruded strands, containing perfectly wetted fibers of uniform length, eliminate the need for the mixing operation in an extrusion compounder. The attempt to preserve the initial fiber length during processing reised interest in the origin of fiber attrition and in optimized processing parameters. Based upon the knowledge that fiber length breakdown takes place mainly during the process of screw plasticating, extrusion trials have been carried out under varied conditions. Fiber length distrubutions and fiber movement within the cross sections of the screw channel along the screw axis have been investigated. It has been shown that screw speed. Pressure and barrel temperature profile, in dependence on screw geometry, show a distinct influence on the residual fiber length. This information provides a description of the prevailing fiber attrition mechanisms and helps define the most suitable hardware and the corresponding adjustment of process parameters to preserve large residual fiber lengt

ISSN:0272-8397    

DOI:10.1002/pc.750150508

出版商:Society of Plastics Engineers, Inc.    

年代:1994

数据来源: WILEY

ISSN:0272-8397    

DOI:10.1002/pc.750150501

出版商:Society of Plastics Engineers, Inc.    

年代:1994

数据来源: WILEY