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Compression fatigue behaviour of fiber composites
GENERAL Acoustic emission monitors damage progression in graphite/epoxy composite structure Bailey, C.D., Freeman, S.M. and Hamilton, J.M. Jr. Materials Evaluation Vol 38 No 8 (1980) pp 21-27 Acoustic emission flaw source location techniques were successfully used to identify resin cracking and fibre bundle fracture, by comparing signal levels for each damage type with that generated by an a c o u s t i c e m i s s i o n signal simulator. Good correlations were found between types of damage progression and acoustic emission signal amplitudes. Application of accelerated weathering test to glass-fibre reinforced polyester sheets of improved surface durability Yamasaki, R.S., and Blaga, A. Journal of Testing and Evaluation 8 No 4 (1980) p 187 An accelerated weathering test has been applied to three types of commercial glass-fibre reinforced polyester (grp), the durability of which has been improved by the application of various surface finishes. Acrylic lacquer-coated grp shows six types of surface damage. The first three have been verified on outdoor exposure. Gel-coated grp underwent degredation characterized by surface micro-cracking, which was confirmed by o u t d o o r exposure. Polyvinylflouride-coated grp underwent five types of surface damage, two of which have been verified by outdoor exposure. In all cases, accelerated weathering reduced the exposure time (compared with outdoor exposure) significantly. Bounds of effective thermal conductivity of short-fibre composites Nomura, S., and Chou, Tsu-Wei Journal o f Composite Materials Vol 14 (April 1980) p 120 This paper presents bounds of effective thermal conductivities for multicomponent, unidirectional, short-fibre composites, based upon an approach originally developed by the authors for composite effective elastic moduli. The results are compared with expressions obtained by Kroner, Zeller and Dederichs, and Hashin and Shtrikman. Complex moduli of chopped fibre and continuous fibre composites: comparison of measurements with estimated bounds Gibson, R.F. and Yau, A. Journal o f
COMPOSITES. APRI L 1981
Composite Materials Vol 14 (April 1980) p 155 Measured dynamic, complex moduli of two E-glass/polyester chopped fibre composites, an E-glass/polyester hybrid chopped/continuous fibre composite and an E-glass/epoxy continuous fibre composite are compared with estimated bounds on the moduli. The loss modulus of the chopped fibre and hybrid composites is higher than predicted. Compression fatigue behaviour of fiber composites Kan, H.P. and Ratwani, M.M. SAMPE Quarterly Vol 11 No 4 (July 1980) pp 10-14 The compression fatigue behaviour of g r a p h i t e / e p o x y c o m p o s i t e s was examined. Two laminates, one fibredominated and the other matrixdominated, were tested under room temperature dry and wet environmental conditions. The effects of specimen geometry, stress ratio, test environments and loading conditions on fatigue life were e x p e r i m e n t a l l y observed. Ultrasonic non-destructive testing was used to determine the damage propagation during fatigue loading. Compressive strength of carbon, glass and Kevlar m 49 fibre reinforced polyester resins Piggott, M.R. and Harris, B. Journal o f Materials Science Vol 15 (1980) pp 2523-2538 The compression behaviour of a series of polyester resins of varying composition reinforced with carbon, glass and aromatic polyamide fibres was made. The test specimens were cylindrically shaped, pultruded and unidirectionally reinforced. At a Vf of 0.3, Kevlar fibres behaved as though their compression modulus and strength were much smaller than their tensile modulus and strength, while carbon fibre composites were only slightly less stiff and weaker in compression than in tension. Creep of laminated aluminium composites Moore, W. and Davies, T.J. Metallurgical Transactions Vol l l A No 8 (August 1980) pp 1439-1446 An account of some mechanical properties, with an emphasis on the creep behaviour, of laminate system consisting of alternative layers of pure aluminium and sintered aluminium powder sheet (SAP) is given. The dependence of the creep behaviour of these multilayer laminates on temperature, applied stress, and volume frac-
tion of SAP is discussed. A study of the fracture surfaces of the laminates is also included. Determination of torsion strength and shear moduli of a multi-layer composite Stoffler, G. Journal o f Composite Materials Vol 14 (April 1980) p 95 A method of determining the three shear moduli by successive approximation from the three principal directions of an orthotropic laminate by means of a simple torsional test performed on square cross-section test specimens is described. The method can be used to check the quality of the laminate as well as provide design parameters. A dielectric study of cellulose fibres Dutta, A.K., Mukherjee, P.S. and Mitra, G.B. Journal of Materials Science Vol 15 (1980) pp 1856-1860 The dielectric constant and loss factor of cellulose fibres from ramie, hemp, and jute were measured in the longitudinal and transverse directions. The ratio of dielectric constant to loss factor is higher in the longitudinal direction indicating higher crystailinity, and the higher mobility of dipoles in this direction is the cause of anistropy in the fibres. The diffusion of moisture in graphite fiber reinforced epoxy laminates Tajima, Y.A. SAMPE Quarterly Vol 11 No 4 (July 1980) pp 1-9 The effects of hygrothermal cycling on the solubility and diffusivity of vapour and liquid water in graphite fibrereinforced epoxy laminates were studied. Sorption in un-aged laminates was found to be simple Fickian (ie, constant diffusion coefficient). The first desorption is F i c k i a n w i t h a concentration -dependent diffusion coefficient. The diffusion process continues to change with hygrothermal conditioning and may become Class I1 diffusion (anomalous). Dynamic mechanical analysis of fiber reinforced composites Reed, K.E. Polymer Composites Vol 1 No 1 (September 1980) pp 44-49 Dynamic mechanical and thermal properties of unidirectional glass/epoxy composites were determined for various fibre orientations. In low angle and longitudinal specimens, a transition was observed above the resin glasstransition temperature which was manifested mechanically as an additional damping peak and thermally as a change in the coefficient of thermal expansion. The new transition has been
147
COMPOSITES. APRI L 1981
Composite Materials Vol 14 (April 1980) p 155 Measured dynamic, complex moduli of two E-glass/polyester chopped fibre composites, an E-glass/polyester hybrid chopped/continuous fibre composite and an E-glass/epoxy continuous fibre composite are compared with estimated bounds on the moduli. The loss modulus of the chopped fibre and hybrid composites is higher than predicted. Compression fatigue behaviour of fiber composites Kan, H.P. and Ratwani, M.M. SAMPE Quarterly Vol 11 No 4 (July 1980) pp 10-14 The compression fatigue behaviour of g r a p h i t e / e p o x y c o m p o s i t e s was examined. Two laminates, one fibredominated and the other matrixdominated, were tested under room temperature dry and wet environmental conditions. The effects of specimen geometry, stress ratio, test environments and loading conditions on fatigue life were e x p e r i m e n t a l l y observed. Ultrasonic non-destructive testing was used to determine the damage propagation during fatigue loading. Compressive strength of carbon, glass and Kevlar m 49 fibre reinforced polyester resins Piggott, M.R. and Harris, B. Journal o f Materials Science Vol 15 (1980) pp 2523-2538 The compression behaviour of a series of polyester resins of varying composition reinforced with carbon, glass and aromatic polyamide fibres was made. The test specimens were cylindrically shaped, pultruded and unidirectionally reinforced. At a Vf of 0.3, Kevlar fibres behaved as though their compression modulus and strength were much smaller than their tensile modulus and strength, while carbon fibre composites were only slightly less stiff and weaker in compression than in tension. Creep of laminated aluminium composites Moore, W. and Davies, T.J. Metallurgical Transactions Vol l l A No 8 (August 1980) pp 1439-1446 An account of some mechanical properties, with an emphasis on the creep behaviour, of laminate system consisting of alternative layers of pure aluminium and sintered aluminium powder sheet (SAP) is given. The dependence of the creep behaviour of these multilayer laminates on temperature, applied stress, and volume frac-
tion of SAP is discussed. A study of the fracture surfaces of the laminates is also included. Determination of torsion strength and shear moduli of a multi-layer composite Stoffler, G. Journal o f Composite Materials Vol 14 (April 1980) p 95 A method of determining the three shear moduli by successive approximation from the three principal directions of an orthotropic laminate by means of a simple torsional test performed on square cross-section test specimens is described. The method can be used to check the quality of the laminate as well as provide design parameters. A dielectric study of cellulose fibres Dutta, A.K., Mukherjee, P.S. and Mitra, G.B. Journal of Materials Science Vol 15 (1980) pp 1856-1860 The dielectric constant and loss factor of cellulose fibres from ramie, hemp, and jute were measured in the longitudinal and transverse directions. The ratio of dielectric constant to loss factor is higher in the longitudinal direction indicating higher crystailinity, and the higher mobility of dipoles in this direction is the cause of anistropy in the fibres. The diffusion of moisture in graphite fiber reinforced epoxy laminates Tajima, Y.A. SAMPE Quarterly Vol 11 No 4 (July 1980) pp 1-9 The effects of hygrothermal cycling on the solubility and diffusivity of vapour and liquid water in graphite fibrereinforced epoxy laminates were studied. Sorption in un-aged laminates was found to be simple Fickian (ie, constant diffusion coefficient). The first desorption is F i c k i a n w i t h a concentration -dependent diffusion coefficient. The diffusion process continues to change with hygrothermal conditioning and may become Class I1 diffusion (anomalous). Dynamic mechanical analysis of fiber reinforced composites Reed, K.E. Polymer Composites Vol 1 No 1 (September 1980) pp 44-49 Dynamic mechanical and thermal properties of unidirectional glass/epoxy composites were determined for various fibre orientations. In low angle and longitudinal specimens, a transition was observed above the resin glasstransition temperature which was manifested mechanically as an additional damping peak and thermally as a change in the coefficient of thermal expansion. The new transition has been
147