摘要:

AbstractTensile and short beam shear tests were performed on five high strength vinyl ester molding compounds after immersion in water at various temperatures. These tests were conducted in order to characterize the degradation of these properties with environmental exposure and to isolate problem areas which contribute to the degradation. Reductions of up to 70 percent were found for both tensile and short beam shear strength, when tested at high temperatures. This loss of properties is primarily a result of degradation of the glass/resin interface and is essentially irreversible.

ISSN:0272-8397    

DOI:10.1002/pc.750030102

出版商:Society of Plastics Engineers, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe change in viscoelastic response of an unsaturated polyester during the course of thickening with magnesium oxide was evaluated, Rheological measurements were obtained to describe the effects of thickening as functions of time and magnesium oxide concentration. Previous researchers have made similar evaluations utilizing Brookfield viscosities. However, the test geometry asociated with a Brookfield T‐bar spindle is not well defined and data interpretation is consequently obscured. A Rheometrics Thermal Mechanical Spectrometer was used to obtain dynamic mechanical measurements ranging across three decades of frequency. Values of the elastic shear modulus,G′, the viscous shear modulus,G″, and the complex viscosity, η*, were calc

ISSN:0272-8397    

DOI:10.1002/pc.750030103

出版商:Society of Plastics Engineers, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractAxial fatigue of two, commercial, talc‐filled polypropylenes was studied. A significant result of our investigation was the identification and characterization of the failure mechanisms and the effects of frequency and hysteretic heating. Frequency was found to be important to the fatigue response of the polymers. At low frequency, fatigue failure appeared to be a process of crack initiation and growth with very little dissipative heating. At high frequency, the fatigue process was dominated by dissipative heating resulting in significant creep and modulus loss, and failure was much accelerated and due mainly to material softening and melting. Correlation of temperature rise with on‐line energy loss in selected experiments enabled us to extract information from the fatigue process. The results provided some quantitative understanding of the different fatigue failure mechanisms at low and high frequenc

ISSN:0272-8397    

DOI:10.1002/pc.750030104

出版商:Society of Plastics Engineers, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractTwo sheet molding compounds, one containing 65 weight percent E‐glass fiber and no filler (SMC‐65) and the other containing 50 weight percent glass and 15 weight percent CaCO3filler were subjected to sinusoidal, load‐control, tension‐tension fatigue. The macroscopic behavior showed some notch sensitivity for both materials, but particularly for SMC‐65. The extent of failure damage over the specimen length decreased with decreasing load amplitude. Different failure mechanisms appear to operate under high‐ and low‐cycle fatigue conditions. Microscopic surface damage studies at stresses near the endurance limit showed several stages in the fatigue failure. For SMC‐65, these stages are, sequentially, matrix crack initiation and growth, matrix pulverization, fiber fracture, and fiber pullout. A similar, but less distinct pattern was observed for SMC‐50. Acoustic emission was also followed during fatigue cycling near the endurance limit. Distinct amplitude distribution peaks for each failure process were seen. It is suggested that matrix fracture, permanent deformation and Euler buckling are all important in high cycl

ISSN:0272-8397    

DOI:10.1002/pc.750030105

出版商:Society of Plastics Engineers, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractMatrix‐dominated mechanical behavior of a graphite/epoxy composite has been found to be affected by sub‐Tgannealing. Postcured (±45°)4Sspecimens of Thornel 300 graphite/Narmco 5208 epoxy were quenched from aboveTgand given a sub‐Tgannealing at 140°C for times up to 105min. The ultimate tensile strength, strain‐to‐break, and toughness of the composite material were found to decrease as functions of sub‐Tgannealing time. No weight loss was observed during the sub‐Tgannealing. The time‐dependent change in mechanical behavior is explained on the basis of free‐volume changes that are related to the physical aging of the nonequilibrium glassy network‐epoxy. The results imply possible changes in composite proper

ISSN:0272-8397    

DOI:10.1002/pc.750030106

出版商:Society of Plastics Engineers, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe behavior of polymeric materials reinforced by discontinuous. Descriptors for the planar and axial orientation distributions are discussed. Predictions of micromechanical models and experimental data are presented to illustrate the influence of orientation state upon elastic constants, thermal coefficients of expansion and tensile strength. Results are presented for the notched strength and compressive creep behavior of the glass/phenolic composite of two orientation states. Finally, the implications of these results upon the design of elements molded of discontinuous fiber composites are discussed.

ISSN:0272-8397    

DOI:10.1002/pc.750030107

出版商:Society of Plastics Engineers, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractA complete stress analysis and reliable failure criteria are essential for important structural applications of composites in order to fully utilize their unique properties. The inhomogeneity, anisotropy and inelasticity of many composites make the use of experimental methods indispensable. Among the experimental techniques, transmission photoelasticity has been extended to birefringent composites in recent years. The extension is not straight‐forward, in view of the complex nature of the photoelastic response of such model materials. This paper very briefly reviews the important developments in the subject and then describes the theoretical basis for a new method of determining the individual values of principal stresses in composite models. The mehod consists in drilling very small holes at points where the state of stress has to be determined. Experiments are then described which verify the theoretical predictions. The limitations of the method are pointed out and it is concluded that valuable information concerning the state of stress in a composite model can be obtained through the suggested metho

ISSN:0272-8397    

DOI:10.1002/pc.750030108

出版商:Society of Plastics Engineers, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe effect of water and isooctane absorption on the flexural fatigue strength of a sheet molding compound (SMC‐R30) is investigated. Absorption of water reduces the fatigue life of specimens of SMC‐R30 as compared to the fatigue life of specimens tested in air. Absorption of isooctane reduces the fatigue life much more than absorption of wa

ISSN:0272-8397    

DOI:10.1002/pc.750030109

出版商:Society of Plastics Engineers, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractBonding and bolting strengths of a sheet molding compound (SMC‐R30) are investigated. Epoxy adhesives are found to give good bonding strength. Surface pretreatment does not affect bond strength. Artificial weathering has practically no effect upon bond strength. Bolting strength depends on the width of the specimen for a certain bolt size. Bolting gives stronger joints than bondin

ISSN:0272-8397    

DOI:10.1002/pc.750030110

出版商:Society of Plastics Engineers, Inc.    

年代:1982

数据来源: WILEY

ISSN:0272-8397    

DOI:10.1002/pc.750030101

出版商:Society of Plastics Engineers, Inc.    

年代:1982

数据来源: WILEY