摘要:

AbstractMaterial parameters in anisotropic rectangular plates are determined in a nondestructive way. Real‐time, TV‐holography is used to determine frequencies and shapes of the first five modes of vibration of plates with free‐free boundary conditions. According to rules given in the paper, finite element analysis is then used to determine two effective Young's moduli, the shear modulus, and the Poisson's

ISSN:0272-8397    

DOI:10.1002/pc.750120502

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractMaterial parameters of anisotropic plates are determined. Rectangular anisotropic plates are tuned by changing the quotient between the length of the sides, so that the second and third modes of vibration, for free‐free boundary conditions, degenerate into the well‐known cross‐shaped and ring‐shaped modes, respectively. The first three modes of vibrations for these plates are determined by optical methods. The propagation of bending waves, generated by the impact of a ballistic pendulum on the plates, has also been optically studied. It is found that bending waves generated in the middle of the tuned plates will reach the boundaries of the plates simultaneously. This gives a relationship between main material parameters. Using this relation and Rayleigh's method for the first three modes of vibrations, the main material parameters for the plates, that is, the effective two Young's moduli, the shear modulus, and the Poisson's ratio, are det

ISSN:0272-8397    

DOI:10.1002/pc.750120503

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractAn improved internal reflection infrared spectroscopy (ATR) technique (1) has been found to be effective for measuring the relative concentrations of polyester and polystyrene (resin) and calcium carbonate filler on sheet molding compound (SMC) surfaces. The technique has been used to determine the effect of molding conditions on the surface compositions of three commercial SMC materials. The surface compositions of two of the materials, of the same formulation but obtained from different sources, were the same and were unaffected by molding conditions. The surface of the third material (or a different formulation) was found to have substantially less resin than the first two materials. The surface composition of the third material varied with molding conditions, the greatest uniformity being obtained with high molding temperatures and pressures. This study has shown that the ATR technique is suitable for determining the relative surface compositions of SMC formulations. This method will be used to correlate the SMC surface composition to SMC properties, such as surface appearance, paintability, and adhesive bond durability.

ISSN:0272-8397    

DOI:10.1002/pc.750120504

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractFor the determination of toughness properties of HDPE/glass fiber and HDPE/cotton fiber composites, an instrumented Charpy impact test has been used. The interpretation of impact load‐deflection curves has been carried out with several concepts of fracture mechanics. Here the limits of linear elastic fracture mechanic (LEFM) have been shown. The change of toughness properties with increasing fiber volume can be described for short fiber reinforced composites with the help of theJ‐integral concept in a suitable mode. An application of the conventional Charpy impact test will result in an overestimation of material behavior because of the energy of crack propagation. With the help of a micromechanical model to describe failure processes, taking account of energy dissipative processes, it is possible to calculate fracture mechanical material parameters. Because of the peculiarities of deformation and fracture behavior, the application of elastic‐plastic fracture mechanic (EPFM)‐concepts for fiber reinforced polymers is r

ISSN:0272-8397    

DOI:10.1002/pc.750120505

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractThe ultimate strength of certain thermoplastic matrix laminates is observed to be strongly dependent upon the stacking sequence. Such effects are thought to be due to the development and action of through‐thickness stresses at the edges of laminates. However, the action of such stresses is not normally considered in Classical Laminate Theory. This paper describes experimental studies of the development of damage in, and subsequent failure of, a family of laminates that exhibit “through‐thickness” effects. Important differences between the mode of failure and development of damage prior to failure are identified, and these observations correlated with other workers' predictions concerning the presence and actions of edge s

ISSN:0272-8397    

DOI:10.1002/pc.750120506

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractThe effect of water absorption on the stress transferability across E‐glass fiber/nylon 6 interface has been studied using the embedded single fiber composite technique. The behavior of silane coated fiber and untreated fiber composites after periods of water immersion were compared. The silane coating provided both higher interfacial shear stress transferability and protection from permanent water damage in the interphase region. It was found that water absorption in the nylon matrix reduced the shear stress transferability through plasticization of the matrix, weakening of the interface, and the development of tensile swelling stresses at the phase boundaries. In untreated materials the shear stress transferability was limited by decoupling of the matrix from the broken fiber ends by either interface slippage or local plane strain fracture in the interphase region near the fiber end. In the silane treated materials the shear stress transferability was limited by constrained yielding of the polysiloxane/nylon interphase at the fiber end, thus indicating plasticization of the matrix was the primary factor. After 20 days of water immersion, there was permanent deterioration of stress transferability in the untreated samples, but very little permanent damage in the treated sample

ISSN:0272-8397    

DOI:10.1002/pc.750120507

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractPoly(ether ether ketone) (PEEK) carbon fiber prepreg tapes (APC‐2) have been thermoformed into a hemispherical double curvature part under a variety of processing conditions. Conventional matched die molding using aluminum molds (at 200°C) were not successful in thermoforming acceptable parts. Parts with severe wrinkling and folding were obtained. A novel three‐piece (steel) mold with built‐in sheet clamping arrangement was, therefore, designed and fabricated. This mold was used at 400°C temperature to thermoform parts from preheated preconsolidated laminates. More interestingly, using the above conditions, 8‐ and 16‐ply unconsolidated laminates could bedirectlythermoformed into parts that were microstructurally sound and exhibited good shape conformity. Results suggest a cycle time of 15 min, with scope for further reduction, if mold cooling is employed. Notwithstanding the simplicity of the thermoforming process, such a short cycle time compares quite favorably with cycle times of several hours for conventional thermosetting resin based

ISSN:0272-8397    

DOI:10.1002/pc.750120508

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractThermoforming of a double curvature hemispherical cap‐shaped part from different continuous carbon fiber‐reinforced thermoplastic composite prepregs has been investigated. A novel three‐piece matched die mold was used for shaping the prepregsdirectlyfrom 16‐ply unconsolidated lay‐ups. For poly(ether ether ketone) (PEEK)‐based prepregs, PEEK/graphite fiber unidirectional tapes and commingled knitted three‐dimensional fabric yielded parts that possessed good shape conformity and were free of any major delamination. Encouraging results were also obtained for modified polysulfone (PXM‐8505) based unidirectional fabric as well as PEEK/graphite knitted bidirectional fabrics. Several other prepregs performed rather poorly in forming acceptable quality parts. Fiber alignment was found to be better for fabric prepregs than unidirectional tapes. Both stretching and “draw in” of the material occur during deformation, even though the relative contribution depends strongly on the prepreg form. Our thermoforming studies suggest a cycle time of 10 min or less to form good quality parts, which is an attractive feature, considering that cycle times are typically several hours for conventional t

ISSN:0272-8397    

DOI:10.1002/pc.750120509

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractWe compare two methods for carrying out single‐fiber‐composite tests in which acoustic emission (AE) data are used to monitor the progression of fiber fracture. The AE measurements include event count or arrival‐time data. While the former is more easily instrumented, the latter provides additional information related to the location of fiber flaws and the progression of the fiber fracture pr

ISSN:0272-8397    

DOI:10.1002/pc.750120510

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

ISSN:0272-8397    

DOI:10.1002/pc.750120511

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY