摘要:

AbstractIn contrast to metallic corrosion where electrochemical corrosion mechanisms are dominant, a variety of mechanisms play a role in degradation of fiber reinforced plastic (FRP) structures. Attack may occur by physical or chemical means or by a combination of both. Although some actions of particular attacking species may be quite specific, there are a number of general corrosion mechanisms and broad guidelines that can be established in order to choose a resin suitable for a particular service. Corrosion mechanisms are illustrated by interactions of environments with vinyl ester resins. Attack in non‐aqueous media is often related to chemical similarity between attacking specie and the resin. Among chemically similar resins, the extent of this type of attack is often influenced by the crosslink density of the resin. It is shown that the solubility parameter of the attacking specie is useful in predicting suitability of a resin for service, if the resin has been evaluated by a test sequence in organic media of varying solubility parameters. In aqueous media it is found that physical attack can occur by means of an osmotic permeation of the resin by water. Degradation by pure water is often more severe than that caused by ionic solutions. Such physical attack can cause delamination and blistering of laminates and must be regarded as a potentially serious corrosive mechanism, although not primarily chemical in nature. In addition to physical attack, chemical attack can occur. Saponification by sodium hydroxide and oxidation by sodium hypochlorite are discussed in some detail as examples. It is shown that in both these cases the chemical corrosive process may be inhibited by controlling the physical corrosion process due to wate

ISSN:0032-3888    

DOI:10.1002/pen.760190502

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractFinite element analyses were performed to investigate theoretically the effects of in‐plane and out‐of‐plane eccentricities, bending or twisting, and thickness nonuniformity on the axial stress and strain variations across the width of off‐axis specimens. The results are compared with measured data and are also used to assess the effects of these eccentricities on the fracture stress of off‐axis fiber composites. Guidelines for detecting and minimizing the presence of eccentricities are

ISSN:0032-3888    

DOI:10.1002/pen.760190503

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractA study has been made of the thermal‐oxidative stability of several commercially available carbon fibers. Significant differences in the weight loss behavior were observed in air aging studies run on the bare fibers at 600°F (589 K). The stability of high temperature laminates, such as those based on NR‐150 polyimide precursor solutions, was found to be directly affected by the stability of the reinforcing carbon fibers. In studies carried out to determine the reasons for carbon fiber instability, residual sodium sulfate was found to be the principle destabilizing factor. A mechanism whereby the sodium sulfate promotes the oxidation of carbon in the presence of air is prop

ISSN:0032-3888    

DOI:10.1002/pen.760190504

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractA test method has been developed to evaluate resin‐glass composite materials for their resistance to environmental, thermal and hydrolytic stresses, humidity, radiation, and immersion in aggressive fluids. The advantages this method offers are ease of specimen preparation, small specimen size, and maximum exposure of resin, glass and interface to the test environmen

ISSN:0032-3888    

DOI:10.1002/pen.760190505

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractA study has been made of the origin of unexpected moisture effects on crack extension in fiberglass laminates. Water immersion has been found to greatly reduce the rate of crack growth under constant loading while increasing the rate under cyclic loading, the latter effect being the expected one. Observations were made of the extension of the stable damage zone at the tip of precut notches in wet and dry environments. The damage zone size is postulated as a critical element in the relaxation of high stress concentrations in composites, such as those at notch or crack tips. Under constant load, moisture is shown to greatly expand the interply delamination region in the damage zone, thus reducing the local fiber stresses and increasing crack resistance. Under cyclic loading moisture has little effect on the delamination region, which is large even for dry environments, and the only effect is weakening of the material and acceleration of cracks. Severe hygrothermal conditions can so weaken the material that the crack resistance is reduced under constant loading as well.

ISSN:0032-3888    

DOI:10.1002/pen.760190506

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractAn experimental investigation is described of the effects of moisture and a polar solvent upon the changes in the axial dimensions of composite tubes fabricated with S‐glass and an epoxy resin. Test parameters included different axial stress levels, sorption variations, and changes in the short‐beam shear strength with moisture variations. Several wetting and drying cycles were used to establish the reproducibility and reversible characteristics of the observed dimensional changes. Test results are compared and discussed with findings reported by other investigat

ISSN:0032-3888    

DOI:10.1002/pen.760190507

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThe coefficient of thermal expansion (CTE) of nylon‐6 reinforced with particulate filler, short glass fibers, and long‐to‐continuous glass fibers was measured between −30 and 170°C. As the reinforcement level, the reinforcement aspect ratio, or degree of orientation increases, the linear CTE decreases. TheTgrange for the composite system is equal to theTgfor the pure nylon‐6 matrix. An unexpected result is observed when the nylon‐6 is reinforced with long or continuous glass fibers in random planar orientation and the weight fraction of reinforcement exceeds 10 percent. In this case, the longitudinal linear CTE (parallel to the plane of the fibers) above theTgis lower than the longitudinal linear CTE below theTg. Analysis of the mathematical descriptions of composite thermal behavior indicates that an extremely low composite modulus in the transverse direction above theTgmay be a cause for this low CTE. The differences in CTE between short fiber and long fiber reinforced compositions indicate that the critical fiber length for thermal stress transfer may be higher than the critical fiber length for mechanical str

ISSN:0032-3888    

DOI:10.1002/pen.760190508

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThis report describes an ultrasonic‐acoustic technique used to measure a “stress wave factor” in order to nondestructively assess the quality of composite structures. In a prior study this factor was found effective in evaluating the interlaminar shear strength of fiber‐reinforced composites. Details of the method used to measure the stress wave factor are described. In addition, frequency spectra of the stress waves are analyzed in order to indicate the nature of the wave phenomena involved. The stress wave factor can be measured with simple contact probes requiring only one‐side access to a part. This is beneficial in nondestructive evaluations because the waves can run parallel to fiber directions and thus, in many cases, measure material properties in directions assumed by actual loads. Moreover, the technique can be applied where conventional through transmission techniques are impractical or where more quantitative data are required. The stress wave factor was measured for a series of graphite polyimide composite panels and results obtained are compared with through transmission immersion ultraso

ISSN:0032-3888    

DOI:10.1002/pen.760190509

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThe optimization of end product properties of fiberglass reinforced engineering thermoplastics must be based upon knowledge of the constituents, including the fiber length distribution. This paper presents the techniques developed for the recovery, dispersal and length distribution analysis of glass fibers recovered from filled engineering resins. An automatic image analyzing computer system is used for the determination. The tedious manual method of measurement from optical photomicrographs is replaced by a rapid, quantitative and reproducible analysis.

ISSN:0032-3888    

DOI:10.1002/pen.760190510

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760190501

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY