摘要:

AbstractThe mechanical properties of the uniaxial and continuous composite with high strain to fracture PP matrix reinforced with the Fe40Ni40B20(at%) and Metglas 2605SC metallic glass ribbons have been determined and compared with the rule of mixtures. The reinforcing ribbons were coated with PVA (polyvinlyl alcohol) to improve interfacial bonding. The experimental fracture strength results for both types of reinforcement deviate from the values predicted. The strength of composite at the fracture strain of ribbon determined experimentally obeys a modified rule of mixture (isostrain condition) for both types of reinforcement over the entire volume fraction range of reinforcement (up to 16%). The experimental composite eleastic modulus results for composite reinforced with relatively narrow Fe40Ni40B20ribbons are found to be generally near the values predicted by the rule of mixtures, but for the Metglas 2605SC wide the modified rule of mixtures, which takes into account the thermally induced tensile stresses at the interface resulting from the mismatch of the coefficients of thermal expansion.

ISSN:0272-8397    

DOI:10.1002/pc.750140402

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractDamage development in plates of a glass fiber‐reinforced polypropylene is recorded, using short pulse photography, during instrumented falling weight tests using the excess energy approach. It is seen that the damage is progressive throughout the test but its initiation cannot be detected either by freeze‐frame photography or visual observation. Specimens are therefore subjected to low‐energy impact followed by microscopic observation of the tensile face. It is found that the initial damage mechanism is cracking of the matrix at the fiber‐matrix interface, the crack propagating along the fiber. The finite element method is used to estimate the stress distributions at damage initiation in 4‐ply and 8‐ply samples cut from unidirectional and cross‐ply plaques. The computed results indicate that initial damage occurs when the transverse tensile stress reaches a c

ISSN:0272-8397    

DOI:10.1002/pc.750140403

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractSeveral surface treatments, using both commercially available coupling agents and reagents containing multiple amines, were applied to commingled continuous as‐received AS4 carbon reinforcing fiber/liquid crystal polymer (LCP) matrix fibers. Unidirectional composites (normally 60 vol% carbon fiber) were prepared from as‐received and treated commingled fibers and characterized. To estimate the effect the effect of the treatments on fiber‐matrix adhesion, short beam shear (SBS) tests were conducted, the failure surfaces were examined, and spectroscopic studies wee performed. The mean SBS strength of the as‐received unidirectional AS4 carbon fiber/LCP matrix composite system was 49 MPa. The best coupling agent and amine treatments yielded increases in composite shear strength of ∼ 10 to 20%, relative to the as‐received AS4/LCP system. For the amine treatments, ESCA and FTIR analyses suggested of both the carbon and LCP fibers may have caused the increased adhesion. Moreover, SEM analysis of the failure surfaces of SBS specimens from composites prepared with the treated fibers may have caused the increased adhesion. Moreover, SEM analysis of the failure surfaces of SBS specimens from composites prepared with the treated fibers (both with coupling agents and amines) showed that strong fiber‐matrix adhesion was present. That is, failure occurred in the LCP ma

ISSN:0272-8397    

DOI:10.1002/pc.750140404

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractVarious electrochemical surface treatments, designed to improve the fiber‐matrix adhesion, were applied to commingled as‐received continuous AS4 carbon reinforcing fiber/liquid crystal polymer (LCP) matrix fibers. Unidirectional composite plates (norminally 60 vol% carbon fiber) were fabricated and short beam shear (SBS) tests were conducted to provide an indication of the effect of the treatments on AS4 carbon fiber‐LCP matrix adhesion. The mean SBS strength of the as‐received AS4/LCP system was 49 MPa. Three elecrtrochemically polymerized coatings‐poly‐para‐phenylene (PPP), polyphenylene oxide (PPO), and polyaniline (PA)‐were applied. Only the PPO coating, however, had a beneficial effect on the composite shear strength. The coating enhanced the shear strength by 14% relative to the as‐received AS4/LCP system. Scanning electronMicroscope (SEM) observations of the PPOtreated shear failure surface indicated the presence of a strong fiber‐matrix bond. That is, the failure location was in the

ISSN:0272-8397    

DOI:10.1002/pc.750140405

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractThree types of glass/nylon 6 intermediate material forms‐film stacking, uncommingled yarn, and commingled yarm‐were selected study the correlations between the impregnating property and mechanical properties. The size of the glass fiber block to be filled with matrix and the porosity in glass fiber bundles by spearing out the fiber bundle was different in these materials. Unidirectional glass fiber reinforced thermoplastic composites were fabricated by compression molding. The being test was performed by using the three‐point loading system, and the fracture behavior and the degree of impregnation were observed to examine the influence of processing conditions on the bending properties, relative to the form of the intermediate material. Bending strength increased, in accordance with the impregnating property, least in the film stacking form, second most in uncommingled yarn, and most in commingled yarn. The impregnating property was affected by the size of fiber blocks and the porosity in fiber bundles, because bending strength was improved by spreading out the fiber bundles. Commingled yarn is an excellent intermediate materials, which has both the fineness of matrix/fiber mixing and large porosity in fiber bu

ISSN:0272-8397    

DOI:10.1002/pc.750140406

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper presents an improved self‐consistent method for estimating the permeability of an aligned fiber assembly, in both longitudinal and transverse directions. In this method an insertion is assumed to include open space surrounded by densely packed fibers. This improvement allows us to describe effectively the permeability of dense structures containing distributed voids. As used in self‐consistent methods, the insertion is placed into a homogeneous medium with an unknown permeability. Stokes flow and Darcy flow are then considered, respectively, at different regions. Boundary and interface conditions as well as two consistency conditions, including the total amount of the flow and the dissipation energy, are applied accordingly. The permeability is solved from these considerations. This improved permeability model captures the flow characteristics of a fiber bundle. In the longitudinal flow case, the openings within a bundle due to disturbance dominate the flow path. In the transverse flow case, the gaps between neighboring fibers govern the flow resistance. The derived expression for the transverse permeability contains two variables, the averaged fiber volume fraction and the maximum packing efficiency, which adequately describe the status of a fiber bundle. These two variables can also be measured experimentally. The predictions agree with available data reported. The result for the longitudinal flow shows not only the influence of these two parameters, but also the very strong effect of the openings within the bundle on the permeability. This explains the significant differences between the data of idealized packings, such as square and hexagonal packing, and those measured from real fiber bundles. The comparison also provides an estimation of the average opening sizes within a fiber bundle as a function of fiber volume fraction. Numerical simulation results of previous studies are also used to verify this appro

ISSN:0272-8397    

DOI:10.1002/pc.750140407

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractThe effect of aging by immersion in water at 60°C on polyester and vinylester resins, unreinforced and reinforced with glass fibers, was investigated. Changes in weight, glass transition temperature, secondary relaxations, and storage modulus, as well as loss modulus were measured, and the environmental effects on these parameters were assessed. Moreover, the chemical structure changes of the materials during aging were studied by the use of IR spectra. The evolution of the physico‐chemical and the mechanical properties as a function of the aging time was established. The results indicate the importance of the matrix morphology, the structure regularity, the presence of the fibers on the water diffusion mechanisms, and the thermomechanical properties through gravimetric changes, DSC, DMA and IR experimen

ISSN:0272-8397    

DOI:10.1002/pc.750140408

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractA model has been developed for analyzing resin impregnation of fiber tows during resin transfer molding of bi‐directional nonwoven fiber performs. The model is based on the existence of two main regions of resin flow: the macropore space formed among fiber tows and the micropore space formed among individual fiber filaments within a tow. The large difference in permeability between these two regions of flow leads to the potential for void formation during resin transfer molding. The model was formulated for both constant flow rate and constant pressure mold filling. For ambient pressure mold filling, the model predicts a difference in the size of the voids and distribution between axial tows (oriented along the flow direction) and transverse tows (oriented in the transverse direction). When vacuum is imposed on the mold, the model predicts the same resin impregnation behavior for both axial and transverse tows. Furthermore, given sufficient time, voids generated under vacuum mold filling will eventually collapse because of the absence of an opposing internal void pressure. In addition to insights on void formation, the model also provides a basis for the study of the relationship between resin transfer molding parameters and the resin impregnation proces

ISSN:0272-8397    

DOI:10.1002/pc.750140409

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractIncomplete fiber wetting in a resin transfer molded composite may result in poor surface finish, high void content, and reduced mechanical properties. This work studied the use of tows that are precoated with a powdered version of the liquid molding resin (towpregs). The goal is to see if such preforms improve the final part properties because of better fiber wetting. Hercules 12K AS‐4 fibers and PR500 (liquid) and PS500 (Powder) resins (3M) were used to make fabrics from towpregs containing 50 wt% total resin (liquid and powder combined). The powder fractions were 0, 13, 21, 50 wt%. Samples were resin transfer molded from preforms made from the towpreg fabrics. Results showed that samples molded with powder‐coated preforms had improved surface finishes and reduced void contents (1.4 vs. 5%), but that the mechanical properties were not improved (transverse moduli of ∼ 7.8 Gpa and axial moduli of ∼ 100 Gpa), probably because of defects inherent in the hand‐woven towpreg fabric that

ISSN:0272-8397    

DOI:10.1002/pc.750140410

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractA description of the hot‐melt prepreg process was developed by coupling resin matrix flow at the coating and impregnation zones with heat transfer considerations. Both bismaleimide (BMI) and epoxy resin systems were used as matrices. With continuous carbon fiber reinforcement. For the laboratory scale prepregger utilized in this study, the thickness of the resin film produced in a doctor blade was approximately 63% of the blade distance, showing good agreement with experimental data. In addition, the measured heat transfer coefficient between prepreg and atmosphere indicated that surface convective resistance is large compared to the internal conductive resistance and thus the chill plate in the prepregging operation plays on important role in determining prepreg quality. By formulating an analytical methodology in terms of the “Prepreg Flow Number” (PFN) that combined important operating parameter (e.g., temperature, pressure, and production rate), a temperature‐pressure‐velocity superposition was confirmed for the prepregging process. In addition, the model could easily be extended to different scales and types of prepregging processes with the aid of dimension‐less parameters that are quite descriptive of the operating conditions employed in prepreg ma

ISSN:0272-8397    

DOI:10.1002/pc.750140411

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY