The commonly accepted production methods of composite systems generally result in departure of th... more The commonly accepted production methods of composite systems generally result in departure of the plies properties from transverse isotropy due to stresses acting during fibre-matrix bond formation. This anisotropy coupled with the composite structure affects compressive loading; the ultimate stresses as well as the direction, in-or out-of-plane, of kink propagation. A unidirectional and a crossply carbon fibre/PEEK composites were compression tested at ambient and elevated temperature as well as exposed to various chemical environments. Significant disruptions in fibre-matrix interface in the crossply composite were indicated. The compression tests showed that failure occurred through in-plane and out-of-plane fibre bucking and kinking in the unidirectional and crossply composites, respectively. Failure of the longitudinal plies in the crossply laminate occurred at significantly higher compression stress than for the unidirectional composite. Compressive failure mechanisms in unidirectional and multi-directional laminates are considered.
L'invention concerne une composition electroconductrice ainsi qu'un procede de production... more L'invention concerne une composition electroconductrice ainsi qu'un procede de production associe, par moulage par injection, par exemple. Cette composition comprend une matrice contenant essentiellement un premier composant thermoplastique, ainsi qu'un second composant thermoplastique possedant une polarite superieure a celle du premier composant thermoplastique. Ce second composant encapsule plusieurs fibres formant un reseau de fibres encapsulees dans la matrice, un composant carbone etant, de preference, attire vers ce second composant, de maniere a rendre electroconducteur ce reseau, dans la matrice.
L'invention concerne une composition electroconductrice ainsi qu'un procede de production... more L'invention concerne une composition electroconductrice ainsi qu'un procede de production associe, par moulage par injection, par exemple. Cette composition comprend une matrice contenant essentiellement un premier composant thermoplastique, ainsi qu'un second composant thermoplastique possedant une polarite superieure a celle du premier composant thermoplastique. Ce second composant encapsule plusieurs fibres formant un reseau de fibres encapsulees dans la matrice, un composant carbone etant, de preference, attire vers ce second composant, de maniere a rendre electroconducteur ce reseau, dans la matrice.
Halloysite nanotubes are employed as nanocarriers of carvacrol, allowing for its high-temperature... more Halloysite nanotubes are employed as nanocarriers of carvacrol, allowing for its high-temperature melt compounding with polyethylene, and resulting in highly potent antimicrobial films.
The electrical resistivity, mechanical properties, outgassing, ion contamination and particle-she... more The electrical resistivity, mechanical properties, outgassing, ion contamination and particle-shedding characteristics of new electrostatic dissipative (ESD) injection moldable thermoplastic composites containing carbon black and glass fibers were studied. The results for polypropylene, ...
IEEE Transactions on Electronics Packaging Manufacturing, 2000
The amount of carbon black required to impart electrical conductivity to an insulating polymer ca... more The amount of carbon black required to impart electrical conductivity to an insulating polymer can be dramatically reduced by its selective localization in a multi-component system which includes the insulating polymer. The present report describes property-structure relationships of polypropylene/nylon/glass fiber (PP/PA/GF) composites with consistent resistivity levels within the 10-10 /sq range achieved at very low carbon black loadings (less than 2%). The quaternary composites studied structure spontaneously during the hot compounding/processing steps and have unique triple-percolation structures. The results were compared with typical carbon black filled materials, which usually contain 15 to 20 wt% carbon black and are too conductive to meet the 10-10 /sq range.
Fibers can greatly improve the mechanical properties of polymers but may also severely weaken mol... more Fibers can greatly improve the mechanical properties of polymers but may also severely weaken molded parts at their weld-line compared to their bulk strength. The tensile properties and fiber orientation of injection and compression molded fiber reinforced Noryl and polypropylene samples with and without a weld-zone were studied. Distinct differences in structure and mechanical properties of weldcontaining and weld-free samples were identified. In unfilled Noryl and unfilled polypropylene, the presence of a weld-line was found to only have a small effect on the tensile strength and modulus, while in the corresponding fiber reinforced systems, orientation of the fibrous reinforcement parallel to the weld-line caused a significant reduction of the tensile strength compared to the weld-free products. The strength ratio of welded and unwelded specimens was found to decrease with increasing fiber concentration. Quantitative determination of the glass fiber orientation distribution within the weld-line region and in the bulk was carried out by analyzing photomicrographs of polished sections at desired locations.
Journal of Thermoplastic Composite Materials, 1989
Mechanical properties of short fiber reinforced thermoplastics depend on fiber length and fiber o... more Mechanical properties of short fiber reinforced thermoplastics depend on fiber length and fiber orientation distribution produced during melt flow processing. The incorporation of short fibers into thermoplastic polymer melts increases their viscosity and the presence of fibers, increasing in length, results also in an increasing viscosity. Breakage of glass fibers during flow through a rheometer, also a serious problem in melt processing of short fiber reinforced thermoplastics, is demonstrated and analyzed. Short fibers greatly improve the mechanical properties of polymers, but may severely weaken molded parts at their weld-line. A quantitative determination of the glass fiber ori entation distribution in the weld-line region was done by analyzing photomicrographs of polished sections. Fiber orientation parallel to the weld-line, normal to the flow direction, causes a dramatic loss of tensile strength. Another factor playing an important role in fiber-filled thermoplastics is the ...
The commonly accepted production methods of composite systems generally result in departure of th... more The commonly accepted production methods of composite systems generally result in departure of the plies properties from transverse isotropy due to stresses acting during fibre-matrix bond formation. This anisotropy coupled with the composite structure affects compressive loading; the ultimate stresses as well as the direction, in-or out-of-plane, of kink propagation. A unidirectional and a crossply carbon fibre/PEEK composites were compression tested at ambient and elevated temperature as well as exposed to various chemical environments. Significant disruptions in fibre-matrix interface in the crossply composite were indicated. The compression tests showed that failure occurred through in-plane and out-of-plane fibre bucking and kinking in the unidirectional and crossply composites, respectively. Failure of the longitudinal plies in the crossply laminate occurred at significantly higher compression stress than for the unidirectional composite. Compressive failure mechanisms in unidirectional and multi-directional laminates are considered.
L'invention concerne une composition electroconductrice ainsi qu'un procede de production... more L'invention concerne une composition electroconductrice ainsi qu'un procede de production associe, par moulage par injection, par exemple. Cette composition comprend une matrice contenant essentiellement un premier composant thermoplastique, ainsi qu'un second composant thermoplastique possedant une polarite superieure a celle du premier composant thermoplastique. Ce second composant encapsule plusieurs fibres formant un reseau de fibres encapsulees dans la matrice, un composant carbone etant, de preference, attire vers ce second composant, de maniere a rendre electroconducteur ce reseau, dans la matrice.
L'invention concerne une composition electroconductrice ainsi qu'un procede de production... more L'invention concerne une composition electroconductrice ainsi qu'un procede de production associe, par moulage par injection, par exemple. Cette composition comprend une matrice contenant essentiellement un premier composant thermoplastique, ainsi qu'un second composant thermoplastique possedant une polarite superieure a celle du premier composant thermoplastique. Ce second composant encapsule plusieurs fibres formant un reseau de fibres encapsulees dans la matrice, un composant carbone etant, de preference, attire vers ce second composant, de maniere a rendre electroconducteur ce reseau, dans la matrice.
Halloysite nanotubes are employed as nanocarriers of carvacrol, allowing for its high-temperature... more Halloysite nanotubes are employed as nanocarriers of carvacrol, allowing for its high-temperature melt compounding with polyethylene, and resulting in highly potent antimicrobial films.
The electrical resistivity, mechanical properties, outgassing, ion contamination and particle-she... more The electrical resistivity, mechanical properties, outgassing, ion contamination and particle-shedding characteristics of new electrostatic dissipative (ESD) injection moldable thermoplastic composites containing carbon black and glass fibers were studied. The results for polypropylene, ...
IEEE Transactions on Electronics Packaging Manufacturing, 2000
The amount of carbon black required to impart electrical conductivity to an insulating polymer ca... more The amount of carbon black required to impart electrical conductivity to an insulating polymer can be dramatically reduced by its selective localization in a multi-component system which includes the insulating polymer. The present report describes property-structure relationships of polypropylene/nylon/glass fiber (PP/PA/GF) composites with consistent resistivity levels within the 10-10 /sq range achieved at very low carbon black loadings (less than 2%). The quaternary composites studied structure spontaneously during the hot compounding/processing steps and have unique triple-percolation structures. The results were compared with typical carbon black filled materials, which usually contain 15 to 20 wt% carbon black and are too conductive to meet the 10-10 /sq range.
Fibers can greatly improve the mechanical properties of polymers but may also severely weaken mol... more Fibers can greatly improve the mechanical properties of polymers but may also severely weaken molded parts at their weld-line compared to their bulk strength. The tensile properties and fiber orientation of injection and compression molded fiber reinforced Noryl and polypropylene samples with and without a weld-zone were studied. Distinct differences in structure and mechanical properties of weldcontaining and weld-free samples were identified. In unfilled Noryl and unfilled polypropylene, the presence of a weld-line was found to only have a small effect on the tensile strength and modulus, while in the corresponding fiber reinforced systems, orientation of the fibrous reinforcement parallel to the weld-line caused a significant reduction of the tensile strength compared to the weld-free products. The strength ratio of welded and unwelded specimens was found to decrease with increasing fiber concentration. Quantitative determination of the glass fiber orientation distribution within the weld-line region and in the bulk was carried out by analyzing photomicrographs of polished sections at desired locations.
Journal of Thermoplastic Composite Materials, 1989
Mechanical properties of short fiber reinforced thermoplastics depend on fiber length and fiber o... more Mechanical properties of short fiber reinforced thermoplastics depend on fiber length and fiber orientation distribution produced during melt flow processing. The incorporation of short fibers into thermoplastic polymer melts increases their viscosity and the presence of fibers, increasing in length, results also in an increasing viscosity. Breakage of glass fibers during flow through a rheometer, also a serious problem in melt processing of short fiber reinforced thermoplastics, is demonstrated and analyzed. Short fibers greatly improve the mechanical properties of polymers, but may severely weaken molded parts at their weld-line. A quantitative determination of the glass fiber ori entation distribution in the weld-line region was done by analyzing photomicrographs of polished sections. Fiber orientation parallel to the weld-line, normal to the flow direction, causes a dramatic loss of tensile strength. Another factor playing an important role in fiber-filled thermoplastics is the ...
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