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Melt processible fluoropolymer composites
damage from a hard steel ball travelling at several different velocities, and the cracking patterns obtained studied in conjunction with numerical results from a 2D plane-strain analysis for a wide plate impacted by a cylindrical impactor. The stress field obtained approximates to the local stress field in an impact region, and is useful in identifying areas of stress concentration. Detailed damage observations help to establish the importance of transverse shear stress in crack initiation.
Imperfection sensitivity of fibre-reinforced, composite, thin cylinders Simitses, G.J., Shaw, D, Sheinman, I. and Girl, J. Composites Science and Technology Vol22 No4 (1985) pp 259-276 The imperfection sensitivity of thin cylindrical shells made from composite material and subjected to uniform axial compression, and the effects upon it of certain parameters, were investigated mathematically. The effect of inplane transverse boundary conditions and load eccentricity on the imperfection sensitivity of boron/epoxy laminated cylindrical shells was investigated. The influence of stacking sequence on the strength of bonded CFRP single lap joints Matthews, F.L and Tester, T.T. International Journal of Adhesion and Adhesives Vol 5 No 1 (January 1985) pp 13-18 The effect of changing the stacking sequence in 0/+45 ° lay-up carbon fibre-reinforced plastic adherends on the joint strength of bonded single lap joints is discussed. The results of a limited experimental study are presented and it is found that both lay-up and stacking sequence influence strength. A correlation between experiment and theory is found to exist for 8-ply laminates but not for 6-ply laminates. Matrix cracking and stiffness reduction during the fatigue of a (0/90)s GFRP laminate Ogin, S.L, Smith, P.A. and Beaumont. P.W.R. Composites Science and Technology Vol 22 No l (1985) pp 25-31 Stiffness reduction due to matrix cracking in (0/90)s glass fibre-reinforced plastic (GFRP) laminate was studied under both quasi-static and fatigue loading, The stiffness reduction is shown to be directly proportional to the density of cracks which accumulate in the transverse ply. A model for the transverse ply crack growth during fatigue gives good agreement with the experimentally determined stiffness reduction curves. (Authors' abstract). Melt processible fluoropolymer composites Altland, R., Carreno, C. and Tebay, J. Materials Engineering Vol 101 (May 1985) p 41 Copolymerization technology has enabled fluorocarbons to become processible by conventional melting techniques. The range of fluorinated polymers retain the unique properties of their higher viscosity precursors, and have the advantage of attractive fibre reinforcements. The melt-processible matrices (fluorinated ethylene, propylene and perfluorinated alkoxy polytetrafluorethylene) achieve higher bond strengths with reinforcing fibres. The thermal, mechanical and chemical resistance properties of these composites are discussed. Mierostruetural efficiency and fracture toughness of short fibre/thermoplastic matrix composites Friedrich, K. Composites Science and Technology 11o122 No 1 (1985) pp 43-74 The fracture behaviour of composites with
340
thermoplastic matrices of differing fracture toughness was examined in detail, particularly with regard to the effect of volume fraction, orientation and distribution of the reinforcing short glass fibres. In general, it was found that an increase in composite toughness can be expected with increasing extent of reinforcement if the matrix is in a brittle condition and if the fibres are well bonded and mostly oriented perpendicular to the crack front.
Polypruylene composites: fracture mechanical analysis of impact strength Bramuzzo, M., Savadori, A. and Bacci, D. Polymer Composites Vol 6 No 1 (January 1985) pp 1-8 An investigation using linear elastic fracture mechanics principles was carried out to determine the impact resistance of polyproylene (PP) containing various fillers. A homopolymer PP containing differing amounts of calcium carbonate, talc or glass spheres and a block copolymer PP modified with EP rubber and containing fillers were tested and compared. An SEM analysis of the fractured surfaces was made. The best results were obtained with calcium-carbonate filled PP. Processing-property relationships in compression molding of sheet molding compounds Oh, S.Y. and Han, C.D. Polymer Composites Vol 6 No I (January 1985) pp 13-19 An experimental investigation was carried out to determine the relationships between processing variables and the mechanical properties of compression moulded sheet moulding compounds (SMC). The polyester resin matrix remained the same throughout the investigation; types of glass fibre and thermoplastic low-profile additives were varied, as were the cure time. mould temperature and mould pressure. Tensile properties, impact strength and dynamic mechanical properties of the resulting composites were examined. It was found, interalia~ that an optimum cure time and mould temperature existed for achieving composites of the greatest tensile and impact strengths. Response of polymeric materials to thermal radiation Share, S. and Baba, A. SAMPE Journal Vo121 No 2 (March~April 1985) pp 7-11 The response of polymeric materials to concentrated solar radiation was investigated. Various plastics, elastomers and composites including graphite/polyimide, graphite/epoxy, graphite/PPQ, glass/epoxy and polyaramid/ epoxy were investigated. Most were found to char. Results are compared and discussed. Rubber toughening of plastics. Part 8 Effects of glass beads on the kinetics of creep in ABS Bucknall, C.B. and Reddock, S.E, Journal of Materials Science Vo120 (April 1985) p 1434 Creep measurements were made on ABS blends containing 0 to 20% by volume of g0 p,m glass beads. At low strains the beads reinforce ABS. Upon increasing the strain and bead content, however, debonding occurs resulting in a rapid drop in composite modulus. The presence of stress concentrations results in increases in creep rate which can be correlated using the Eyring equation. It is concluded that debonded glass beads accelerate multiple crazing by increasing stresses in the matrix(and this resembles rubber particles). It is shown that debonded beads drastically reduce the impact strength of the composite.
Salicylic acid modified high performance epoxy matrices Ibrahim, A.M. and Seferis, J.C. Polymer Composites Vol 6 No 1 (January 1985) pp 47-53 The effect of the presence of salicylic acid on the cure of epoxy systems which may be used as matrices for carbon fibre composites is reported. Stress dependence of the coefficient of moisture diffusion in composite materials Neumann, S. and Marom, G. Polymer Composites Vol 6 No 1 (January 1985) pp 9:-12 A model to express the effect of external loading on diffusion into the bulk resin matrix of unidirectional composite materials is proposed and confirmed for calculations made for glass fibre-reinforced epoxy composites, Structural repair systems for thermoplastics composites Welder, S.M., Lause, H.J. and Fountain, R. SAMPE Quarterly Vol 16 No 2 (January 1985) pp 33-36 The advantages of using thermoplastic composites as replacement materials for aluminium alloys in structural components in aerospace systems are briefly described. One advantage, the possibility of on-site repairs, is further discussed. Candidate methods of achieving repairs - - magnetic heat induction, adhesive bonding, ultrasonic welding, spin/vibration welding, and inert gas welding-- are described. Thermophysical properties of asbestos reinforced rubbers Loftus, P., O'Donnell, J., Wostenholm, G.H., Yates, B., Badami, D.V, and Green, D.Journalof Materials Science Vol 20 (March 1985) p 1093 An experimental study has been made into the sealing characteristics of gaskets made from asbestos-reinforced rubber. The work contains three separate investigations of the thermal properties of the material Two of these were associated with optimizing the moisture uptake for sealing characteristics; and the third was concerned with the composite cure. The measurements provide information which is relevant to thermally induced structural changes in these composite components. Ultrasonic inspection of carbon-epoxy composites Hagemaier, D.J, and Fassbender, 1LH.Materials Evaluation Vo143 No 5 (April 1985) p 556 Laminate and honeycomb structures are subjected to various ultrasonic techniques. Reference standards, with built-in defects, were used which establish test sensitivity and defect detectability. In addition, it is urged meaningful acceptance/rejection criteria must be established for an efficient inspection. Steps are taken to clarify this process for both fabrication and in-service defects. Use of statical identntion laws in the impact analysis of laminated composite plates Tan, T.M. and Sun, C.T. Transactions of the ASME: Journal of Applied Mechanics Vo152 No 1 (March 1985) pp 6-12 The low-velocity impact response of graphite/ epoxy laminates was investigated theoretically and experimentally. A nine-mode isoparametric plate finite element in conjunction with an empirical contact law was used for the theoretical investigation. The theoretical results were in good agreement with strain-gauge experimental data, indicating that the theoretical procedure adequately describes the impact response of graphite/epoxy laminates for low impact velocities.
COMPOSITES. OCTOBER 1985
Imperfection sensitivity of fibre-reinforced, composite, thin cylinders Simitses, G.J., Shaw, D, Sheinman, I. and Girl, J. Composites Science and Technology Vol22 No4 (1985) pp 259-276 The imperfection sensitivity of thin cylindrical shells made from composite material and subjected to uniform axial compression, and the effects upon it of certain parameters, were investigated mathematically. The effect of inplane transverse boundary conditions and load eccentricity on the imperfection sensitivity of boron/epoxy laminated cylindrical shells was investigated. The influence of stacking sequence on the strength of bonded CFRP single lap joints Matthews, F.L and Tester, T.T. International Journal of Adhesion and Adhesives Vol 5 No 1 (January 1985) pp 13-18 The effect of changing the stacking sequence in 0/+45 ° lay-up carbon fibre-reinforced plastic adherends on the joint strength of bonded single lap joints is discussed. The results of a limited experimental study are presented and it is found that both lay-up and stacking sequence influence strength. A correlation between experiment and theory is found to exist for 8-ply laminates but not for 6-ply laminates. Matrix cracking and stiffness reduction during the fatigue of a (0/90)s GFRP laminate Ogin, S.L, Smith, P.A. and Beaumont. P.W.R. Composites Science and Technology Vol 22 No l (1985) pp 25-31 Stiffness reduction due to matrix cracking in (0/90)s glass fibre-reinforced plastic (GFRP) laminate was studied under both quasi-static and fatigue loading, The stiffness reduction is shown to be directly proportional to the density of cracks which accumulate in the transverse ply. A model for the transverse ply crack growth during fatigue gives good agreement with the experimentally determined stiffness reduction curves. (Authors' abstract). Melt processible fluoropolymer composites Altland, R., Carreno, C. and Tebay, J. Materials Engineering Vol 101 (May 1985) p 41 Copolymerization technology has enabled fluorocarbons to become processible by conventional melting techniques. The range of fluorinated polymers retain the unique properties of their higher viscosity precursors, and have the advantage of attractive fibre reinforcements. The melt-processible matrices (fluorinated ethylene, propylene and perfluorinated alkoxy polytetrafluorethylene) achieve higher bond strengths with reinforcing fibres. The thermal, mechanical and chemical resistance properties of these composites are discussed. Mierostruetural efficiency and fracture toughness of short fibre/thermoplastic matrix composites Friedrich, K. Composites Science and Technology 11o122 No 1 (1985) pp 43-74 The fracture behaviour of composites with
340
thermoplastic matrices of differing fracture toughness was examined in detail, particularly with regard to the effect of volume fraction, orientation and distribution of the reinforcing short glass fibres. In general, it was found that an increase in composite toughness can be expected with increasing extent of reinforcement if the matrix is in a brittle condition and if the fibres are well bonded and mostly oriented perpendicular to the crack front.
Polypruylene composites: fracture mechanical analysis of impact strength Bramuzzo, M., Savadori, A. and Bacci, D. Polymer Composites Vol 6 No 1 (January 1985) pp 1-8 An investigation using linear elastic fracture mechanics principles was carried out to determine the impact resistance of polyproylene (PP) containing various fillers. A homopolymer PP containing differing amounts of calcium carbonate, talc or glass spheres and a block copolymer PP modified with EP rubber and containing fillers were tested and compared. An SEM analysis of the fractured surfaces was made. The best results were obtained with calcium-carbonate filled PP. Processing-property relationships in compression molding of sheet molding compounds Oh, S.Y. and Han, C.D. Polymer Composites Vol 6 No I (January 1985) pp 13-19 An experimental investigation was carried out to determine the relationships between processing variables and the mechanical properties of compression moulded sheet moulding compounds (SMC). The polyester resin matrix remained the same throughout the investigation; types of glass fibre and thermoplastic low-profile additives were varied, as were the cure time. mould temperature and mould pressure. Tensile properties, impact strength and dynamic mechanical properties of the resulting composites were examined. It was found, interalia~ that an optimum cure time and mould temperature existed for achieving composites of the greatest tensile and impact strengths. Response of polymeric materials to thermal radiation Share, S. and Baba, A. SAMPE Journal Vo121 No 2 (March~April 1985) pp 7-11 The response of polymeric materials to concentrated solar radiation was investigated. Various plastics, elastomers and composites including graphite/polyimide, graphite/epoxy, graphite/PPQ, glass/epoxy and polyaramid/ epoxy were investigated. Most were found to char. Results are compared and discussed. Rubber toughening of plastics. Part 8 Effects of glass beads on the kinetics of creep in ABS Bucknall, C.B. and Reddock, S.E, Journal of Materials Science Vo120 (April 1985) p 1434 Creep measurements were made on ABS blends containing 0 to 20% by volume of g0 p,m glass beads. At low strains the beads reinforce ABS. Upon increasing the strain and bead content, however, debonding occurs resulting in a rapid drop in composite modulus. The presence of stress concentrations results in increases in creep rate which can be correlated using the Eyring equation. It is concluded that debonded glass beads accelerate multiple crazing by increasing stresses in the matrix(and this resembles rubber particles). It is shown that debonded beads drastically reduce the impact strength of the composite.
Salicylic acid modified high performance epoxy matrices Ibrahim, A.M. and Seferis, J.C. Polymer Composites Vol 6 No 1 (January 1985) pp 47-53 The effect of the presence of salicylic acid on the cure of epoxy systems which may be used as matrices for carbon fibre composites is reported. Stress dependence of the coefficient of moisture diffusion in composite materials Neumann, S. and Marom, G. Polymer Composites Vol 6 No 1 (January 1985) pp 9:-12 A model to express the effect of external loading on diffusion into the bulk resin matrix of unidirectional composite materials is proposed and confirmed for calculations made for glass fibre-reinforced epoxy composites, Structural repair systems for thermoplastics composites Welder, S.M., Lause, H.J. and Fountain, R. SAMPE Quarterly Vol 16 No 2 (January 1985) pp 33-36 The advantages of using thermoplastic composites as replacement materials for aluminium alloys in structural components in aerospace systems are briefly described. One advantage, the possibility of on-site repairs, is further discussed. Candidate methods of achieving repairs - - magnetic heat induction, adhesive bonding, ultrasonic welding, spin/vibration welding, and inert gas welding-- are described. Thermophysical properties of asbestos reinforced rubbers Loftus, P., O'Donnell, J., Wostenholm, G.H., Yates, B., Badami, D.V, and Green, D.Journalof Materials Science Vol 20 (March 1985) p 1093 An experimental study has been made into the sealing characteristics of gaskets made from asbestos-reinforced rubber. The work contains three separate investigations of the thermal properties of the material Two of these were associated with optimizing the moisture uptake for sealing characteristics; and the third was concerned with the composite cure. The measurements provide information which is relevant to thermally induced structural changes in these composite components. Ultrasonic inspection of carbon-epoxy composites Hagemaier, D.J, and Fassbender, 1LH.Materials Evaluation Vo143 No 5 (April 1985) p 556 Laminate and honeycomb structures are subjected to various ultrasonic techniques. Reference standards, with built-in defects, were used which establish test sensitivity and defect detectability. In addition, it is urged meaningful acceptance/rejection criteria must be established for an efficient inspection. Steps are taken to clarify this process for both fabrication and in-service defects. Use of statical identntion laws in the impact analysis of laminated composite plates Tan, T.M. and Sun, C.T. Transactions of the ASME: Journal of Applied Mechanics Vo152 No 1 (March 1985) pp 6-12 The low-velocity impact response of graphite/ epoxy laminates was investigated theoretically and experimentally. A nine-mode isoparametric plate finite element in conjunction with an empirical contact law was used for the theoretical investigation. The theoretical results were in good agreement with strain-gauge experimental data, indicating that the theoretical procedure adequately describes the impact response of graphite/epoxy laminates for low impact velocities.
COMPOSITES. OCTOBER 1985