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Stress field in and around a coated short fiber in an infinite matrix subjected to uniaxial and biaxial loadings
changes in signal amplitude by traditional C-scan analysis or by noting changes in the feature value of a backwall echo in a transmitted signal.
Prediction of tensile matrix failure in composite laminates Flaggs, D.L Journal of Composite Materials Vol 19 No 1 (January 1985) pp 29-50 A mixed-mode strain energy release rate fracture criterion is used together with a 2D shear-lag model to predict tensile matrix failure. Predictions are compared with experimental data for Mode 190 ° ply matrix cracking in (+0/90~)~ laminates and mixed-mode failure in the 0 plies of(0ff0)s T300/934 laminates; good agreement was found. It is concluded that point stress/strain failure criteria are not adequate in predicting tensile matrix failure, and that lamina strength should not refer to a fixed value but depends on parameters such as lamina thickness and stiffness of neighbouring plies. Promising quantitative non destructive evaluation techniques for composite materials Williams Jr, J.H. and Lee, S.S. Materials Evaluation Vo143 No 5 (April 1985) p 561 The state-of-the-art non-destructive techniques of ultrasonics, acoustic emission, thermography and acoustic-ultrasonics are considered. It is proposed that non-destructive evaluation characterization, where the integrated effects of morphological and microstructural states are detected and qualified, provide the opportunity to develop quantitativepredictions of static and fatigue strength. This argument encompasses composite structures which do not contain gross defects. Reinforced plastics/composite: Still growing at 40 English, LK. Materials Engineering Vol 101 (April 1985) p 31 This article summarizes the advancements and points of interest in composite materials at the 40th Annual RP/C Conference held in Atlanta. The chief innovations in resin, fibre, processing and performance technology are discussed. The review is illustrated by recent applications in the many advancing fields of composite materials. A review of the literature on finite-element modelling of laminated composite plates Reddy, J.N. The Shock and Vibration Digest Vol 17 No 4 (April 1985) pp 3-8 A review of the literature on FEM of natural vibrations of plates during the period 19801984 is presented. A historical background of the development of shear deformation theories is included (51 references). Stress concentration factors in unidirectional composites with random fiber spacing Fukuda, H. Composites Science and Technology I/o122 N o 2 (1985) pp 153-163 Based on a modification of Hedgepetffs shearlag equation` a method for determining the statistical value of the stress concentration factor of a composite with random fibre spacing is presented. The results are intended to provide a basis for the statistical prediction of the strength of a composite. Stress field in and around a coated short fiber in an infinite matrix subjected to uniaxial and biaxial Ioadings Mikata, Y. and Taya, M. Transactions of the ASME: Journal of Applied Mechanics Vo152 No 1 (March 1985) pp 19-24
COMPOSITES. OCTOBER 1985
The stresses reduced in and around a coated short fibre composite were investigated using the Boussinesq-Sadowsky stress function. The coated fibre was assumed to consist of two confocal spheroids embedded in an infinite body. It was shown that the stiffness and thickness of the coating and the fibre aspect ratio had some effect on the stress field.
Stretching performance limits with engineering fibers English, L K. Materials Engineering Vo1101 (May 1985) p 51 Commercially available reinforcing fibres are reviewed in this article. The author discusses the relative merits of each fibre type in terms of mechanical properties, cost and fabrication techniques. Fibre developments are reported in polymeric fibres, such as the new ultra high molecular weight polyethylene fibre which exhibits remarkable mechanical properties, and the new ceramic fibres. Two-dimensional modelling of compressive failure in delaminated laminates Chai, H. and Babcock, C,D. Journal of Composite Materials Vol 19 No 1 (January 1985) pp 67-98 An analytical model comprising an elastic stability problem and a fracture problem is developed in order to determine the compressive strength criticality of a near-surface elliptical delamination in a laminated composite. A Rayleigh-Ritz analysis gives a postbuckling solution, and fracture is governed by an energy balance criterion based on selfsimilar debond growth. Propagation and arrest of delamination is controlled by fracture energy, debond depth and elastic properties of the material on both sides of the damage interface. Cracking proceeded in a stable or unstable manner parallel or normal to the loading axis depending on the amount of material anisotropy relative to the loading axis. Ultrasonic and thermographic methods for NDE of composite tubular parts Rogovsky, A,J. Materials Evaluation Vo143 No 5 (April 1985) p 547 Ultrasonic C-scan, hand-held contact and imaging techniques were investigated and applied to determining defect size and location in composite structures containing simulated defects. It is reported that of these, the ultrasonic imaging method was the most efficient. Examples of ultrasonic and infrared imaging of defective areas are presented. Implementation of developed non-destructive techniques to some practical inspection problems are discussed. The viscoelastic behaviour of short fibre composite materials Nomura, S. and Chou, T,W. International lournal of Engineering Science Vol23 No 2 (1985) p 193 In a unidirectional short fibre composite the fibres are considered as ellipsoidal elastic inclusions embedded in a viscoelastic matrix. The static correspondence principle, which relates the viscoelastic problem to the elastic one, is applied to the modified expression of the effective elastic moduli of short fibre composites. Numerical examples for various fibre aspect ratios are presented based on the collocation approximation method. Comparisons of the results with the self-consistent method are also presented.
METAL MATRICES The dynamic mechanical response of fiberreinforced beams to large transverse loads Mosquera~ J.M. and Kolsky, H. Journal of the Mechanics and Physi,'s of Solids Vol33 No 2 (1985) j~p 193-209 Cantilever beams of steel wire-reinforced leadtin alloy are subjected to dynamic transverse loading applied to the tip of the beam. Experimental results are compared with predictions based on theories of Spencer, Jones et al for the response of metal composite beams to large transverse impacts. Impacts are produced by travelling metal "hammers" or by explosive propulsion of small masses onto the beam; the impact is monitored by high-speed photography, strain-gauge measurements of the force and measurements of the position of the tip of the beam. The plastic transverse deflection of the tip and the final position of the plastic wave front compare well with theoretical predictions. Altowance is made tbr the effect ot strain rate in the metal matrix. The formation of the high-melting TiN-Ti composites in the pulse plasma Michalski, A, and Sokolowska, A. Journal of Materials Science Vol 20 (May 1985) p 1842 Composite layers of Ti and its high-melting compounds (TiN~, TiNxCy) were crystallized on steel from a pulse plasma at a temperature <~ 500 K. It was found that the electrode tip was a source of the Ti purl of the composite. The electrode lateral surfaces, covered by Ti compounds, yielded vapours of these compounds and from these vapours crystallization of the second part of the composite proceeded. Since the type of crystallized layer was determined by temperature and pressure in the nucleation region, it can be assumed that a homogeneous TiN nucleation occurs in this plasma between 1800 and 2700 K. The macroscopic electrical properties of in-situ composite superconductors Rakhmanov, A.L. Journal ~f Physics D." Applied Physics Vol 18 (1985) p 919 The effective medium theory has been used to predict the values of the longitudinal and transverse critical current densities for superconducting composites. A threshold value of the superconducting phase concentration is predicted beAow which the transverse superconducting current decreases considerably. The I - V characteristics of in situ composites may be described in terms of a critical state model generalized for the case of anisotropic superconductors. A note of contiguity in sintered WC-Co composites Laugier, M.T. Journal of Materials Science l, etters Vol 4 (March 1985) pp 263-264 The nodular morphology of WC powders is not observed in sintered WC-Co composite. However, because some of these nodules are composed of crystallographically well-aligned WC grains, it would be expected that they would be extremely stable and penetration of Co during sintering would be energetically unfavourable. The author states that these stable aggregates are possibly a source of potential weakness in these composites. Static stress concentrations due to broken fibres in metal matrix composites with intermediate interfacial bonding strength Ochiai, S.. Abe, K, and Osamura K. ZeitschHft
337
Prediction of tensile matrix failure in composite laminates Flaggs, D.L Journal of Composite Materials Vol 19 No 1 (January 1985) pp 29-50 A mixed-mode strain energy release rate fracture criterion is used together with a 2D shear-lag model to predict tensile matrix failure. Predictions are compared with experimental data for Mode 190 ° ply matrix cracking in (+0/90~)~ laminates and mixed-mode failure in the 0 plies of(0ff0)s T300/934 laminates; good agreement was found. It is concluded that point stress/strain failure criteria are not adequate in predicting tensile matrix failure, and that lamina strength should not refer to a fixed value but depends on parameters such as lamina thickness and stiffness of neighbouring plies. Promising quantitative non destructive evaluation techniques for composite materials Williams Jr, J.H. and Lee, S.S. Materials Evaluation Vo143 No 5 (April 1985) p 561 The state-of-the-art non-destructive techniques of ultrasonics, acoustic emission, thermography and acoustic-ultrasonics are considered. It is proposed that non-destructive evaluation characterization, where the integrated effects of morphological and microstructural states are detected and qualified, provide the opportunity to develop quantitativepredictions of static and fatigue strength. This argument encompasses composite structures which do not contain gross defects. Reinforced plastics/composite: Still growing at 40 English, LK. Materials Engineering Vol 101 (April 1985) p 31 This article summarizes the advancements and points of interest in composite materials at the 40th Annual RP/C Conference held in Atlanta. The chief innovations in resin, fibre, processing and performance technology are discussed. The review is illustrated by recent applications in the many advancing fields of composite materials. A review of the literature on finite-element modelling of laminated composite plates Reddy, J.N. The Shock and Vibration Digest Vol 17 No 4 (April 1985) pp 3-8 A review of the literature on FEM of natural vibrations of plates during the period 19801984 is presented. A historical background of the development of shear deformation theories is included (51 references). Stress concentration factors in unidirectional composites with random fiber spacing Fukuda, H. Composites Science and Technology I/o122 N o 2 (1985) pp 153-163 Based on a modification of Hedgepetffs shearlag equation` a method for determining the statistical value of the stress concentration factor of a composite with random fibre spacing is presented. The results are intended to provide a basis for the statistical prediction of the strength of a composite. Stress field in and around a coated short fiber in an infinite matrix subjected to uniaxial and biaxial Ioadings Mikata, Y. and Taya, M. Transactions of the ASME: Journal of Applied Mechanics Vo152 No 1 (March 1985) pp 19-24
COMPOSITES. OCTOBER 1985
The stresses reduced in and around a coated short fibre composite were investigated using the Boussinesq-Sadowsky stress function. The coated fibre was assumed to consist of two confocal spheroids embedded in an infinite body. It was shown that the stiffness and thickness of the coating and the fibre aspect ratio had some effect on the stress field.
Stretching performance limits with engineering fibers English, L K. Materials Engineering Vo1101 (May 1985) p 51 Commercially available reinforcing fibres are reviewed in this article. The author discusses the relative merits of each fibre type in terms of mechanical properties, cost and fabrication techniques. Fibre developments are reported in polymeric fibres, such as the new ultra high molecular weight polyethylene fibre which exhibits remarkable mechanical properties, and the new ceramic fibres. Two-dimensional modelling of compressive failure in delaminated laminates Chai, H. and Babcock, C,D. Journal of Composite Materials Vol 19 No 1 (January 1985) pp 67-98 An analytical model comprising an elastic stability problem and a fracture problem is developed in order to determine the compressive strength criticality of a near-surface elliptical delamination in a laminated composite. A Rayleigh-Ritz analysis gives a postbuckling solution, and fracture is governed by an energy balance criterion based on selfsimilar debond growth. Propagation and arrest of delamination is controlled by fracture energy, debond depth and elastic properties of the material on both sides of the damage interface. Cracking proceeded in a stable or unstable manner parallel or normal to the loading axis depending on the amount of material anisotropy relative to the loading axis. Ultrasonic and thermographic methods for NDE of composite tubular parts Rogovsky, A,J. Materials Evaluation Vo143 No 5 (April 1985) p 547 Ultrasonic C-scan, hand-held contact and imaging techniques were investigated and applied to determining defect size and location in composite structures containing simulated defects. It is reported that of these, the ultrasonic imaging method was the most efficient. Examples of ultrasonic and infrared imaging of defective areas are presented. Implementation of developed non-destructive techniques to some practical inspection problems are discussed. The viscoelastic behaviour of short fibre composite materials Nomura, S. and Chou, T,W. International lournal of Engineering Science Vol23 No 2 (1985) p 193 In a unidirectional short fibre composite the fibres are considered as ellipsoidal elastic inclusions embedded in a viscoelastic matrix. The static correspondence principle, which relates the viscoelastic problem to the elastic one, is applied to the modified expression of the effective elastic moduli of short fibre composites. Numerical examples for various fibre aspect ratios are presented based on the collocation approximation method. Comparisons of the results with the self-consistent method are also presented.
METAL MATRICES The dynamic mechanical response of fiberreinforced beams to large transverse loads Mosquera~ J.M. and Kolsky, H. Journal of the Mechanics and Physi,'s of Solids Vol33 No 2 (1985) j~p 193-209 Cantilever beams of steel wire-reinforced leadtin alloy are subjected to dynamic transverse loading applied to the tip of the beam. Experimental results are compared with predictions based on theories of Spencer, Jones et al for the response of metal composite beams to large transverse impacts. Impacts are produced by travelling metal "hammers" or by explosive propulsion of small masses onto the beam; the impact is monitored by high-speed photography, strain-gauge measurements of the force and measurements of the position of the tip of the beam. The plastic transverse deflection of the tip and the final position of the plastic wave front compare well with theoretical predictions. Altowance is made tbr the effect ot strain rate in the metal matrix. The formation of the high-melting TiN-Ti composites in the pulse plasma Michalski, A, and Sokolowska, A. Journal of Materials Science Vol 20 (May 1985) p 1842 Composite layers of Ti and its high-melting compounds (TiN~, TiNxCy) were crystallized on steel from a pulse plasma at a temperature <~ 500 K. It was found that the electrode tip was a source of the Ti purl of the composite. The electrode lateral surfaces, covered by Ti compounds, yielded vapours of these compounds and from these vapours crystallization of the second part of the composite proceeded. Since the type of crystallized layer was determined by temperature and pressure in the nucleation region, it can be assumed that a homogeneous TiN nucleation occurs in this plasma between 1800 and 2700 K. The macroscopic electrical properties of in-situ composite superconductors Rakhmanov, A.L. Journal ~f Physics D." Applied Physics Vol 18 (1985) p 919 The effective medium theory has been used to predict the values of the longitudinal and transverse critical current densities for superconducting composites. A threshold value of the superconducting phase concentration is predicted beAow which the transverse superconducting current decreases considerably. The I - V characteristics of in situ composites may be described in terms of a critical state model generalized for the case of anisotropic superconductors. A note of contiguity in sintered WC-Co composites Laugier, M.T. Journal of Materials Science l, etters Vol 4 (March 1985) pp 263-264 The nodular morphology of WC powders is not observed in sintered WC-Co composite. However, because some of these nodules are composed of crystallographically well-aligned WC grains, it would be expected that they would be extremely stable and penetration of Co during sintering would be energetically unfavourable. The author states that these stable aggregates are possibly a source of potential weakness in these composites. Static stress concentrations due to broken fibres in metal matrix composites with intermediate interfacial bonding strength Ochiai, S.. Abe, K, and Osamura K. ZeitschHft
337