ISSN:0272-8397    

DOI:10.1002/pc.750010102

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractX‐rays can be used to measure residual as well as applied stresses in polymers and reinforced polymeric composites by diffracting from filler particles that are embedded before curing. We have investigated various fillers that exhibit suitable stress‐induced shifts of diffraction angle when embedded in uniaxial graphite fiber/epoxy composites. Stresses in the particles determined by X‐rays are proportional to the corresponding composite stresses, in agreement with the model of H. T. Hahn. Results indicate that the stress sensitivity (change in X‐ray strain per MPa applied to the composite) increases in the order W, CdO, Ni, Ag, Nb, Al. The elastic range terminates at a yield point beyond which the stress sensitivity is markedly reduced for metallic fillers, but no such yield point has appeared with CdO particles. Oppositely directed particle strains are seen after unloading from stress levels that have exceeded the yield point. Theoretical predictions for these findings are discussed. Residual stresses in the particles were determined after curing and storage under ambient conditions. In the fiber direction the residual stresses were always found to be positive and larger than the principal stresses orthogonal t

ISSN:0272-8397    

DOI:10.1002/pc.750010103

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractA mechanics theory is developed for predicting the physical thermal, hygral, and mechanical properties (including various strengths) of unidirectional intraply hybrid composites (UIHC) based on unidirectional properties of the constituent composites. Procedures are described which can use this theory in conjunction with composite mechanics computer codes and general purpose structural analysis finite element programs for the analysis/design of structural components made from intraply hybrid angleplied laminates (IHAL). Comparisons with limited data show that this theory predicts mechanical properties of UIHC and flexural stiffnesses of IHAL which are in good agreement with experimental data. The theory developed herein makes it possible to design and optimize structural components from IHAL based on a large class of available constituent fibers.

ISSN:0272-8397    

DOI:10.1002/pc.750010104

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractImproved products can be obtained from sheet molding compounds (SMC) if due regard is given to the geometry of the molding charge relative to the product shape. For example, it is possible to position designed charge shapes in the mold to produce moldings without weld‐lines and without substantially altering the initial fiber orientation of the SMC matrix. This paper describes theoretical and experimental work which has developed a charge shape calculation procedure for molding two‐dimensional SMC components weld‐line free without substantially altering the SMC‐matrix glass fiber orientation. The two main parts of the work are; (i) The theoretical development of a charge shape calculation procedure for molding symmetrical and unsymmetrical plaques. This includes a mathematical description of the compression flow process, which is used to determine flow front development from mold‐cavity pressure and velocity distributions. (ii) The results of experimental work which test the mathematical description of the compression flow process, and charge shape calculation procedure. These results include mold pressure measurements from an instrumented mold, fiber distribution and orientation measurements, and SMC‐material tensile strength

ISSN:0272-8397    

DOI:10.1002/pc.750010105

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractComputerized infrared analysis is applied to the characterization of a glass‐reinforced crosslinked polyester. The method of factor analysis determines the number of independent components which constitute the polymeric matrix. Subsequently, the spectra of those components are fitted by a least‐squares criterion to spectra of the multicomponent matrix, or, if the glass spectrum is included as an additional component, to the spectra of composites. The least‐squares coefficients yield the matrix composition in terms of the initial reactant composition and the extent of crossli

ISSN:0272-8397    

DOI:10.1002/pc.750010106

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractA testing program was conducted to determine the time‐temperature response of the principal compliances of a unidirectional graphite/epoxy composite. It is shown that two components of the compliance matrix are time and temperature independent. In addition, the compliance matrix is found to be symmetric for the viscoelastic composite. The time‐temperature superposition principle is used to determine shift factors. It is shown that shift factors are independent of fiber orientation for fiber angles that vary from 10 to 90° with respect to the load direc

ISSN:0272-8397    

DOI:10.1002/pc.750010107

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractMineral fillers of flake configuration such as mica can, in principle, produce large increases in modulus and strength especially if the flake is oriented predominantly in a plane. Additionally, the resulting composites have the advantage of possessing isotropic properties in the plane of orientation, thereby minimizing the warpage normally associated with the injection molding of fiber‐reinforced thermoplastics. However, to properly transmit stress from the matrix to the mica and minimize the effect of defects in morphology, a ductile matrix is required with adequate interaction or adhesion between phases. Many of the above conclusions are documented in the literature and are confirmed by our investigations of the system mica‐polypropylene. The novelty of this effort rests upon (1) successful attempts to identify specific non‐silane additives which by co‐blending suitably modify the mica‐polypropylene interface, (2) to demonstrate the remarkable effects of time‐temperature during melt processing on the behavior of this system; and, (3) to show the relation between composition and time‐temperature effects on resultant mechanical, physical, and thermal properties. Most notably, large improvements in tensile and flexural strength and heat distortion temperature can be attributed to the use of small amounts of chlorinated organic compounds blended under carefully selected melt process conditions. Some speculation concerning the mechanism of interaction will be discussed and the resultant potential for increased application will als

ISSN:0272-8397    

DOI:10.1002/pc.750010108

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractDynamic mechanical and thermal properties were determined for unidirectional epoxy/glass composites at various fiber orientation angles. Resonant frequency and relative logarithmic decrement were measured as functions of temperature. In low angle and longitudinal specimens, a transition was observed above the resin glass transition temperature which was manifested mechanically as anadditional damping peak and thermally as a change in the coefficient of thermal expansion. The new transition was attributed to a heterogeneous resin matrix induced by the fiber. The temperature span of the glass‐rubber relaxation was found to broaden with decreasing orientation angle, reflecting the growth of fiber contribution and exhibiting behavior similar to that of Young's modulus. The change in resonant frequency through the glass transition was greatest for samples of intermediate fiber angle, demonstrating behavior similar to that of the longitudinal shear modulu

ISSN:0272-8397    

DOI:10.1002/pc.750010109

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractTests characterizing an epoxy system that contains 5 percent rubber and is suitable for wet‐filament winding are described. The resin is a bisphenol‐A rubberized epoxy diluted with an aliphatic diglycidyl ether and cured with an aromatic amine. The viscosity and pot life were measured and the progress of cure was monitored so an optimum cure could be chosen. Mechanical tests were performed on the cured resin. The low viscosity (0.95 Pa's) and long pot life (29.3 h) make for ease of processing. A cure cycle of 1.5h at 90°C plus 2 h at 130°C gives a cured resin having a glass transition temperature of 104°C. The heat‐cured material has a tensile strength of 76.1 MPa and a modulus of 2.43 GPa. Kevlar 49 composites of 60‐, 65‐, and 70‐volume‐percent fiber were prepared and tested. Results are presented and compared to two other Kevlar 49/

ISSN:0272-8397    

DOI:10.1002/pc.750010110

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractStandard test methods ASTM D‐651 for determining tensile properties and ASTM D‐790 for flexure properties are evaluated. Heterogeneous fiber distributions due to molding flow conditions are shown to yield test specimens wherein fiber orientation near surfaces is highly collimated while orientations in central regions are oriented approximately transverse to the specimen axis. In addition, the converging and diverging flow fields in the dog bone (ASTM D‐651) specimen with end gate are shown to yield a variation in fiber orientation along the specimen length. Finite element analysis of the dog bone (ASTM D‐651) reveals that stress concentrations and a non‐uniform stress distribution are introduced due to the required gripping arrangement of the test standard. The flexural specimen is decomposed into two elements of a collimated and transverse fiber orientations and a mathematical model is developed which reflects the composite behavior of the beam specimen. Finally, it is concluded that the D‐651 and D‐790 test methods do not reveal intrinsic design data for fiber reinforced mold

ISSN:0272-8397    

DOI:10.1002/pc.750010111

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY