摘要:

AbstractGlass fiber reinforced polyester composites, with gelcoat, are widely used as structural materials for hulls, pools, pipes, and tanks in aggressive environments, despite the lack of knowledge concerning their resistance to water in the long term. In addition, these materials may be damaged through an osmotic process, especially when immersed in water, as are boat hulls, and this phenomenon can lead to a delamination of the gelcoat and of the laminate plies. The aim of this experimental study is to evaluate the mechanical characteristics with time of orthotropic laminates subjected to accelerated tests of humid aging. The evolution of the properties with water absorption is followed by a nondestructive test procedure based on vibrational mode analysis. The results are additionally confirmed by quasi‐static bending and shear tests. It is shown that the main effects of water on the composite mechanical properties are the plasticization of the matrix an the osmotic delamination of the plies; on the other hand, gelcoat blistering had no influence on the durability. This paper highlights the need for and the complementarity of both nondestructive and destructive mechanical tests for studying the long‐term behavior of composites in marine environme

ISSN:0272-8397    

DOI:10.1002/pc.750160502

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe five independent stiffness constants,C11,C33,C44,C66, andC13, and the axial and transverse thermal expansivity of unidirectional gel‐spun polyethylene fiber reinforced composites have been measured as functions of fiber volume fractionVf. The axial extensional modulusC33and axial Poisson's ratiov13follow the rule of mixtures, while the axial shear modulusC44, transverse shear modulusC66, and transverse plane‐strain bulk modulusCt( =C11−C66) obey the Halpin‐Tsai equation. Extrapolation toVf= 1 gives the five stiffness constants of gel‐spun polyethylene fiber. The tensile property of the fiber is highly anisotropic, with the axial Young's modulus about 40 times higher than the transverse Young's modulus. In contrast, the axial shear modulus exceeds the transverse shear modulus by only 5%. A similar treatment of the thermal expansivity data in terms of the Schapery equations gives an axial thermal expansivity of −1.25 × 10−5K−1and a transverse thermal expansivity of 11.7 × 10

ISSN:0272-8397    

DOI:10.1002/pc.750160503

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe injection molding ability of long glass fiber reinforced polyamide pellets was studied. The injection moldable materials were produced by a melt impregnation process of continuous fiber rovings. The rovings were chopped to pellets of 9 mm length. Chopped pellets with a variation in the degree of impregnation and fiber concentration were studied. The injection molded samples were analyzed for fiber concentration, fiber length, and fiber orientation. Dumbbell‐shaped tensile bars were made to evaluate the mechanical properties. The fibers in the tensile bars had a high orientation in the flow direction and minor fiber concentration gradients were observed. The fiber lengths decreased with fiber concentration from 1.6 mm for a 2 vol% to 0.6 mm for a 25 vol% system. The tensile and impact properties increased considerably with fiber concentration. A low degree of impregnation in the pellets of the fibers resulted in somewhat lower tensile and impact propertie

ISSN:0272-8397    

DOI:10.1002/pc.750160504

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractGas permeation and creep deformation of a commercial prepreg, which exhibits viscoelastic characteristics, were investigated as a function of time, temperature, and consolidation pressure. Experiments using a prepreg stack demonstrated that the material exhibited a linear viscoelastic bulk deformation under vacuum/autoclave pressure and furthermore, the in‐plane gas flow exhibited non‐Darcian flow behavior with a permeation hysteresis. This behavior was viewed and analyzed by two viscoelastic relaxation processes: (1) bulk dimensional relaxation, and (2) microscopic pore structure rearrangement. A modified standard linear solid (SLS) viscoelastic model was used to interpret the creep compliance and dynamic gas permeability utilizing two independent relaxation parameters. By visual investigation of pore sizes and their distribution, air permeation was found to take place mostly through the interlaminar porosity network for the prepreg system exami

ISSN:0272-8397    

DOI:10.1002/pc.750160505

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractCoventional pultrusion of thermoset composites is under increasing examination for emissions of harmful volatiles from the resin wetout tank. Even though the pultrusion of thermoplastic matrix composites produces no emissions, it is difficult to wet individual fibers due to their high melt viscosities. This paper addresses both the issues of volatiles and wetting with a process called Reaction Injection Pultrusion (RIP). A prototype RIP machine was used to make both thermoplastic polyurethane and thermoset polyisocyanurate matrix composites. The RIP process produces pultruded parts with low void content, good surface finish, and acceptable mechanical properties. The low viscosity constituents used in RIP help improve fiber impregnation, while the small volume of the impregnation bath reduces emissions. Processing parameters such as line speeds, catalyst levels, and die temperaures were varied to establish processing guidelines for sustained production.

ISSN:0272-8397    

DOI:10.1002/pc.750160506

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractLiquid composite molding (LCM) processes such as resin transfer molding and structural reaction injection molding are considered to be high potential processes for the mass production of composite parts. The resin injection step in LCM consists of two simultaneous flows: bulk mold filling and tow wetting. This complexity often results in the entrapment of air in the composite part, which is known to result in degradation of part performance, In this work, systematic investigation of the resin flow behavior through various types of glass fiber reinforcements is carried out by flow visualization. The objective is to relate the fiber mat architecture to the micro scale flow pattern and void formation, movement, and removal. An optical image analysis and processing technique is developed to help quantify void formation. Void formation is related to liquid properties and fiber‐liquid contact angle. Although the focus of the study is LCM, the results can be directly applied to other composite manufacturing processes that involve advancement of resin in a dry fiber reinforcemen

ISSN:0272-8397    

DOI:10.1002/pc.750160507

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractA sequential design optimization scheme based on artificial neural networks (ANN) is proposed. It is a combination of an ANN model and a nonlinear programming algorithm. The proposed scheme is implemented with network training, optimization, and sheet molding compound (SMC) process simulation in a closed loop. A “cyclic coordinate search” technique is employed to initiate the optimization process, to collect training data for the neural network model, and to perform a preliminary design sensitivity analysis. Emphasis is placed on the development of an integrated, automatic optimization‐simulation design tool that does not rely on the designer's experience and interpretation. Testing results based on the design of heating channels in an SMC compression molding tool show that the optimal design can be achieved with fewer data points than other methods, such as factorial design. The efficiency of the ANN method would be greater as the number of design variables

ISSN:0272-8397    

DOI:10.1002/pc.750160508

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractFiber‐reinforced plastic (FRP) pipe has much lower density and better corrosion resistance characteristics than currently used alloy pipe, but it generally does not conduct electricity as well as steel pipe. In this study, an FRP pipe was made conductive by doping the inner liner vinyl ester resin with milled carbon fibers. The joints were also made conductive using the same resin, thus allowing the pipe to be electrically grounded. The result was a pipe having a surface resistivity of less than 125 Ω/□ using current manufacturing proce

ISSN:0272-8397    

DOI:10.1002/pc.750160509

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractComplex fiber‐matrix interactions occur in the processing of glass fiber reinforced polymeric composites, because of the proprietary, complex composition of commercial sizings applied to the glass fiber surface. Research involving a vinyl ester resin system and three model commercial glass fiber sizings, having varying levels of solubility in the resin, has shown that micro‐dielectrometry can provide important information about interactions and may be useful as a tool in optimizing sizing‐matrix resin interactions. Two distinct types of interactions may be monitored by micro‐dielectrometry: The initial resin swelling of the sizing, as well as the dissolution of the sizing into the resin. An estimate of the times associated with swelling and dissolution of the sizing into the matrix resin can be made from micro‐dielectric measurements to optimize composite p

ISSN:0272-8397    

DOI:10.1002/pc.750160510

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractComposites of elastomers and cellulose have been investigated. Copolymers of styrene‐butadiene rubber (SBR) and acrylonitrile‐butadiene rubber (NBR) as well as natural rubber (NR) were compounded with regenerated cellulose (Cellulose II). The technique for the incorporation of filler was based on the coprecipitation of the rubber latex‐cellulose xanthate mixture. Cellulose filler was used in the range of 0 to 30 phr. The best results were shown by the natural rubber‐regenerated cellulose systems. The different behavior of the systems is explained by experimental evidence. The reinforcement mechanism for NR compositions, which involves an induced crystallizing rubber (NR), seems to be different from the mechanism for SBR

ISSN:0272-8397    

DOI:10.1002/pc.750160511

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY