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The present study demonstrates, for the first time, the ability of a 10-ply glass fiber-reinforced polymer composite laminate to operate as a structural through-thickness thermoelectric generator. For this purpose, inorganic tellurium... more
The present study demonstrates, for the first time, the ability of a 10-ply glass fiber-reinforced polymer composite laminate to operate as a structural through-thickness thermoelectric generator. For this purpose, inorganic tellurium nanowires were mixed with single-wall carbon nanotubes in a wet chemical approach, capable of resulting in a flexible p-type thermoelectric material with a power factor value of 58.88 μW/m·K2. This material was used to prepare an aqueous thermoelectric ink, which was then deposited onto a glass fiber substrate via a simple dip-coating process. The coated glass fiber ply was laminated as top lamina with uncoated glass fiber plies underneath to manufacture a thermoelectric composite capable of generating 54.22 nW power output at a through-thickness temperature difference οf 100 K. The mechanical properties of the proposed through-thickness thermoelectric laminate were tested and compared with those of the plain laminates. A minor reduction of approximate...
Many technologies presented in literature for the forming of self-reinforced or all-polymer composites are based on manufacturing processes involving thermoforming of pre-consolidated sheets. This paper describes novel direct forming... more
Many technologies presented in literature for the forming of self-reinforced or all-polymer composites are based on manufacturing processes involving thermoforming of pre-consolidated sheets. This paper describes novel direct forming routes to manufacture simple geometries of self-reinforced, all-polypropylene (all-PP) composites, by moulding fabrics of woven co-extruded polypropylene tapes directly into composite products, without the need for pre-consolidated sheet. High strength co-extruded PP tapes have potential processing advantages over mono-extruded fibres or tapes as they allow for a larger temperature processing window for consolidation. This enlarged temperature processing window makes direct forming routes feasible, without the need for an intermediate pre-consolidated sheet product. Thermoforming studies show that direct forming is an interesting alternative to stamping of pre-consolidated sheets, as it eliminates an expensive belt-pressing step which is normally needed for the manufacturing of semi-finished sheets products. Moreover, results from forming studies shows that only half the energy was required to directly form a simple dome geometry from a stack of fabrics compared to stamping the same shape from a pre-consolidated sheet.
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The creation of highly oriented, coextruded polypropylene (PP) tapes allows the production of novel, wholly thermoplastic, recyclable “all-polypropylene” (all-PP) composites, which possess both a large temperature processing window... more
The creation of highly oriented, coextruded polypropylene (PP) tapes allows the production of novel, wholly thermoplastic, recyclable “all-polypropylene” (all-PP) composites, which possess both a large temperature processing window (>30°C) and a high volume fraction of reinforcement phase (highly oriented PP tapes: >90%). This large processing window is achieved by using coextruded, highly drawn PP tapes. To achieve coherent all-PP composites the interfacial characteristics following consolidation must be understood. This article investigates the interfacial characteristics of these coextruded tapes by using microcomposite models to create interfaces between tapes of varying draw ratios, drawing temperatures, skin/core ratios, and skin layer thicknesses. The tape drawing parameters are seen to control the interfacial properties in subsequent microcomposite models. The failure mode of these specimens, and hence bond strength, varies with consolidation temperature, and a model is proposed describing and explaining this behavior. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 118–129, 2007
Many technologies presented in literature for the forming of self-reinforced or all-polymer composites are based on manufacturing processes involving thermoforming of pre-consolidated sheets. This paper describes novel direct forming... more
Many technologies presented in literature for the forming of self-reinforced or all-polymer composites are based on manufacturing processes involving thermoforming of pre-consolidated sheets. This paper describes novel direct forming routes to manufacture simple geometries of self-reinforced, all-polypropylene (all-PP) composites, by moulding fabrics of woven co-extruded polypropylene tapes directly into composite products, without the need for pre-consolidated sheet. High strength co-extruded PP tapes have potential processing advantages over mono-extruded fibres or tapes as they allow for a larger temperature processing window for consolidation. This enlarged temperature processing window makes direct forming routes feasible, without the need for an intermediate pre-consolidated sheet product. Thermoforming studies show that direct forming is an interesting alternative to stamping of pre-consolidated sheets, as it eliminates an expensive belt-pressing step which is normally needed for the manufacturing of semi-finished sheets products. Moreover, results from forming studies shows that only half the energy was required to directly form a simple dome geometry from a stack of fabrics compared to stamping the same shape from a pre-consolidated sheet.
ABSTRACT The present study focuses on short flax fiber, as well as long flax fiber-reinforced polypropylene (flax/PP) composites, manufactured by the injection molding method. Compounding of flax with two different grades of PP (with and... more
ABSTRACT The present study focuses on short flax fiber, as well as long flax fiber-reinforced polypropylene (flax/PP) composites, manufactured by the injection molding method. Compounding of flax with two different grades of PP (with and without maleic anhydride (MA-PP) grafting) is carried out by four methods: kneading process, Henschel kinetic mixer, extrusion compounding, and production of long fiber thermoplastic (LFT) granules through pultrusion. The effect of the compounding method and injection molding on the fiber length and mechanical properties of the composites is being investigated. Furthermore, the effect of fiber—matrix adhesion on the mechanical response is being discussed. It can be concluded that the reduction in fiber length, associated with injection molding, did not affect the tensile properties significantly for the studied systems due to improvements in fiber orientation along the polymer flow direction and increased fiber efficiency through dimensional changes due to fiber opening. The addition of MA-PP led to improvements in the tensile strength of injection-molded composites. Kneader compounded composites showed maximum tensile strength as well as stiffness when compared with other compounding methods.
The concept of “overheating” is one of the known methods for manufacturing single polymer composites. This concept is validated on two categories of semi-crystalline polymers: the drawable, apolar (i.e., isotactic polypropylene [iPP],... more
The concept of “overheating” is one of the known methods for manufacturing single polymer composites. This concept is validated on two categories of semi-crystalline polymers: the drawable, apolar (i.e., isotactic polypropylene [iPP], ultra-high molecular weight polyethylene [UHMWPE]) and the less drawable, polar ones (i.e., polyethyleneterephalate [PET] and polyamides [PA]). The interchain interactions in apolar polymers are relatively weak and therefore a high degree of drawability can be obtained. Polar polymers on the other hand have relative strong interchain interactions, they are therefore less drawable. A shift higher than 20°C of the melting temperature can be obtained in case of highly extended iPP (draw ratios >14). Ultra-drawn PE shows only 10°C overheating upon constraining and this is mainly due to the change in chain mobility for PE in the hexagonal phase. In case of PET and PA6, only draw ratios of 4 could be reached; however, temperature shifts of about 10°C for constrained fibers compared to unconstrained fibers could be measured. A proof of principle of the potential of the constraining concept for the manufacturing of single polymer composites is obtained by the preparation of single fiber model composites. The effect of the post-drawing conditions on overheating is examined in details on the example of iPP. It is concluded that both post-drawing temperature and ultimate draw ratio have a significant influence on the degree of overheating. POLYM. COMPOS., 26:114–120, 2005. © 2004 Society of Plastics Engineers
The purpose of our study was to clarify the events that take place during anterior cruciate ligament (ACL) failure, focusing on the behavior of the ACL as a composition of multiple fibers, during uniaxial tension along the ligament.Ten... more
The purpose of our study was to clarify the events that take place during anterior cruciate ligament (ACL) failure, focusing on the behavior of the ACL as a composition of multiple fibers, during uniaxial tension along the ligament.Ten fresh-frozen human cadaveric knee specimens were fixed in an Instron machine (Instron, Norwood, MA), and load was applied parallel to the ACL axis. Two cameras were used to detect the failure mode of the ACL and its different groups of fibers. The distinct bundles of fibers were marked in each specimen before testing. The macroscopic findings during the experiment were used for comparison with the biomechanical results.The ACL showed a non-monotonic response during testing. The load-elongation curve showed a plateau or a second peak after the initial drop in load. Macroscopically, some fibers were failing initially, whereas the intact fibers had a remaining load potential. In our setting, 3 different failure patterns were recognized, specifically, a midsubstance tear of the anteromedial or the posterolateral bundle with a subsequent failure of the intact bundle or an initial avulsion of the anteromedial attachment. Analysis of the video frames showed a direct connection between the failure patterns in the load-elongation curves and the macroscopic sequence of events during ACL failure.The ACL ligament acts as a multifiber construction. In our setting, rupture follows 3 specific patterns where a complete or partial tear of the fiber bundles occurs first and the remaining intact fiber bundles have a potential load resistance.Our study allows a better understanding of the mechanical properties of the ACL. An update on the biomechanics of ACL failure during uniaxial tension after the “double-bundle revolution” could provide data helpful for ACL reconstruction.
The creation of highly oriented, co-extruded polypropylene (PP) tapes allows the production of recyclable ‘all-polypropylene’ composites, with a large temperature processing window... more
The creation of highly oriented, co-extruded polypropylene (PP) tapes allows the production of recyclable ‘all-polypropylene’ composites, with a large temperature processing window (>30°C) and a high volume fraction of highly oriented PP (>90%). These composites show little deviation of mechanical properties with compaction temperature. This paper introduces all-polypropylene composites and reports the tensile and compressive properties of unidirectional composites. These
... FSPs are machined steel cylinders which simulate projectiles from fragmentation grenades or shrapnel from explosions [18]. Fig. ... A tape with a skin:core:skin structure is produced by co-extrusion of a ethylene-propylene copolymer... more
... FSPs are machined steel cylinders which simulate projectiles from fragmentation grenades or shrapnel from explosions [18]. Fig. ... A tape with a skin:core:skin structure is produced by co-extrusion of a ethylene-propylene copolymer skin with a polypropylene homopolymer core. ...
Highly oriented polypropylene (PP) tapes, with high tensile strength and stiffness achieved by molecular orientation during solid state drawing are consolidated to create high performance recyclable “all-polypropylene” (all-PP)... more
Highly oriented polypropylene (PP) tapes, with high tensile strength and stiffness achieved by molecular orientation during solid state drawing are consolidated to create high performance recyclable “all-polypropylene” (all-PP) composites. These composites possess a large temperature processing window (>30°C) and a high volume fraction of highly oriented PP (>90%). This large processing window is achieved by using co-extruded, highly drawn PP
The creation of highly oriented, co-extruded polypropylene (PP) tapes allows the production of recyclable “all-polypropylene” (all-PP) composites, with a large temperature processing window... more
The creation of highly oriented, co-extruded polypropylene (PP) tapes allows the production of recyclable “all-polypropylene” (all-PP) composites, with a large temperature processing window (>30°C) and a high volume fraction of highly oriented PP molecules (>90%). This paper describes all-PP composites made from woven tape fabrics and reports the tensile and compressive properties of these, with reference to composite processing conditions
The environmental durability of carbon nanotube (CNT)-modified carbon-fibre-reinforced polymers (CFRPs) is investigated. The key problem of these new-generation composites is the modification of their polymer matrix with nanoscaled... more
The environmental durability of carbon nanotube (CNT)-modified carbon-fibre-reinforced polymers (CFRPs) is investigated. The key problem of these new-generation composites is the modification of their polymer matrix with nanoscaled fillers. It was recently demonstrated that the damage tolerance of these materials, as manifested by their fracture toughness, impact properties, and fatigue life, can be improved by adding CNTs at weight fractions as low as 0.5%. This improvement is mainly attributed to the incorporation of an additional interfacial area between the CNTs and the matrix, which is active at the nanoscale. However, this additional interface could have a negative effect on the environmental durability of the aforementioned systems, since it is well known that the moisture absorption ability of a matrix is enhanced by the presence of multiple interfaces, which serve as an ingress route to water. To examine this problem, CNT-modified CFRPs were exposed to hydrothermal loadings. At specified intervals, the composites were weighted, and the water uptake vs. time was recorded for both the modified and a reference systems. The electrical conductivity of the composites was registered at the same time intervals. After the environmental exposure, the interlaminar shear properties of the conditioned composite systems were measured and compared with those of unmodified composites, as well as with the shear properties of unexposed laminates.
Woven fabric based self-reinforced polypropylene (SRPP) or all-polypropylene (all-PP) composite laminates based on co-extruded tapes were analysed for water uptake and the effect that this had on mechanical properties. Comparisons were... more
Woven fabric based self-reinforced polypropylene (SRPP) or all-polypropylene (all-PP) composite laminates based on co-extruded tapes were analysed for water uptake and the effect that this had on mechanical properties. Comparisons were made to a commercial glass mat reinforced PP (GMT) and natural fibre mat reinforced PP (NMT). Although the all-PP composites described in this paper can show significant water uptake
For Abstract see ChemInform Abstract in Full Text.
This paper discusses the prediction of the residual compressive strength after low velocity impact for different CFRP material systems. Several material systems were examined using each time different types of epoxy matrices and carbon... more
This paper discusses the prediction of the residual compressive strength after low velocity impact for different CFRP material systems. Several material systems were examined using each time different types of epoxy matrices and carbon fibers. Experimental results concerning residual compressive strength after impact for all the material systems are compared here to values predicted by the model developed by the CMG group. Predicted values agree very well with respective experimental results. In addition, in the present work, the influence of stacking sequence, existence and position of interleaves on the solid particle erosion in carbon fiber reinforced epoxy composites (CF/EP) are investigated. The erosive wear behavior was studied in a modified sandblasting apparatus at 90°-impact angle. The erosion behavior was considered as a repeated impact procedure (impact fatigue). Predictions made by the same model for the residual tensile strength after erosion give excellent results.
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