On the static and dynamic properties of flax and Cordenka epoxy composites

Fibre reinforced composites have excellent specific properties and are widely sought after by engineers seeking to reduce mass. However, end of life disposal is a significant problem and so research into more sustainable natural fibre composites is extremely topical. This paper examines the applicability of natural fibre composites for high performance structural applications. Woven flax and regenerated cellulose (Cordenka) textiles were pre-impregnated with commercially available epoxy resins and consolidated into test laminates in an autoclave to determine their static (compressive, tensile, flexural) and dynamic (energy absorption) properties. The range of compressive strengths was 77.5–299.6 MPa. Tensile strengths ranged from 63 to 92.6 MPa and interlaminar shear strength (ILSS) from 10.7 to 23.3 MPa. Specific energy absorption (SEA) varied between 21.2–34.2 kJ/kg. Biotex flax combined with MTM49 resin matched the SEA of T300 carbon fibre using the same resin system and layup. This work has demonstrated that natural fibre composites have significant scope for use in structural applications but additional work is required on fibre to matrix bonding in order to maximise their properties whilst remaining an environmentally credible option

Mechanical, structural and dissolution properties of heat treated thin-film phosphate based glasses

Here we show the deposition of 2.7 μm thick phosphate based glass films produced by magnetron sputtering, followed by post heat treatments at 500 °C. Variations in degradation properties pre and post heat treatment were attributed to the formation of Hematite crystals within a glass matrix, iron oxidation and the depletion of hydrophilic P-O-P bonds within the surface layer. As deposited and heat treated coatings showed interfacial tensile adhesion in excess of 73.6 MPa; which surpassed ISO and FDA requirements for HA coatings. Scratch testing of coatings on polished substrates revealed brittle failure mechanisms, amplified due to heat treatment and interfacial failure occurring from 2.3 to 5.0 N. Coatings that were deposited onto sandblasted substrates to mimic commercial implant surfaces, did not suffer from tensile cracking or trackside delamination showing substantial interfacial improvements to between 8.6 and 11.3 N. An exponential dissolution rate was observed from 0 to 2 h for as deposited coatings, which was eliminated via heat treatment. From 2 to 24 h ion release rates ordered P > Na > Mg > Ca > Fe whilst all coatings exhibited linear degradation rates, which reduced by factors of 2.4–3.0 following heat treatments

Characterisation of CorGlaes (R) Pure 107 fibres for biomedical applications

A degradable ultraphosphate (55 mol % P2O5) quinternary phosphate glass composition has been characterised in terms of its chemical, mechanical and degradation properties both as a bulk material and after drawing into fibres. This glass formulation displayed a large processing window simplifying fibre drawing. The fibres displayed stiffness and strength of 65.5 ± 20.8 GPa and 426±143 MPa. While amorphous discs of the glass displayed a linear dissolution rate of 0.004 mg cm−2 h−1 at 37 °C, in a static solution with a reduction in media pH. Once drawn into fibres, the dissolution process dropped the pH to <2 in distilled water, phosphate buffer saline and corrected-simulated body fluid, displaying an autocatalytic effect with >90 % mass loss in 4 days, about seven times faster than anticipated for this solution rate. Only cell culture media was able to buffer the pH taking over a week for full fibre dissolution, however, still four times faster dissolution rate than as a bulk material. However, at early times the development of a HCA layer was seen indicating potential bioactivity. Thus, although initial analysis indicated potential orthopaedic implant applications, autocatalysis leads to accelerating degradation in vitro

Water absorption properties of phosphate glass fiber-reinforced poly-epsilon-caprolactone composites for craniofacial bone repair

The moisture uptake of polymers and composites has increasing significance where these materials are specified for invasive, long-term medical applications. Here we analyze mass gain and the ensuing degradation mechanisms in phosphate glass fiber reinforced poly-epsilon-caprolactone laminates. Specimens were manufactured using in situ polymerization of epsilon-caprolactone around a bed of phosphate glass fibers. The latter were sized with 3-amino-propyltriethoxysilane to control the rate of modulus degradation. Fiber content was the main variable in the study, and it was found that the moisture diffusion coefficient increased significantly with increasing fiber volume fraction. Diffusion, plasticization, and leaching of constituents appear to be the dominant aspects of the process over these short-term tests. (C) 2007 Wiley Periodicals, Inc

Introducing a novel manufacturing process for automotive structural/semi structural composite components

Potential uses of composite materials are currently being investigated by the automotive industry to reduce vehicle weight and CO2 emissions. Existing composite production processes are however, low volume and high cost. The aim of the present study was to develop a novel end-to-end production process to produce a light weight, cost effective polymer composite with reduced TAKT time and potential for structural applications. Components were produced from discontinuous random fibres mixed with an epoxy resin system. Static and dynamic mechanical testing as well as durability tests are in progress to evaluate the performance of these materials. Initial results were compared to Sheet Moulding Compound (SMC) as the benchmark composite material

Recycled carbon fibre for high performance energy absorption

This paper compares the mechanical properties of virgin and recycled woven carbon fibre prepreg and goes on to assess the potential for recycled carbon fibre reinforced plastic (rCFRP) to be used in high performance energy absorption structures. Three sets of material were examined: fresh containing virgin fibres and resin, aged which was an out of life but otherwise identical roll and recycled which contained recycled fibre and new resin. The compressive strength and modulus of rCFRP were approximately 94% of the values for fresh material. This correlated directly with the results from impact testing where rCFRP conical impact structures were found to have a specific energy absorption of 32.7. kJ/kg versus 34.8. kJ/kg for fresh material. The tensile and flexural strength of rCFRP were 65% of the value for fresh material. Tensile and flexural moduli of rCFRP were within 90% of fresh material and ILSS of rCFRP was 75% that of fresh. Overall rCFRP has been proved to remain a highly satisfactory engineering material. This is a significant finding as it proves that carbon fibre can be recycled and reused in high performance applications. This has significant implications for use of carbon fibre in the automotive industry where End of Life Vehicle (ELV) legislation requires 85% of materials to be recyclable. This work opens the door to significantly expanded use of carbon fibre in the automotive industry. Of equal significance is the finding that the mechanical properties of fresh and aged carbon fibre were all within ±6% of one another. This highlights an opportunity to understand resin system life in more detail in order to prevent the creation of composite waste at source. © 2012 Elsevier Ltd

Influence of compatibilizing agent molecular structure on the mechanical properties of phosphate glass fiber-reinforced PLA composites

Eight compatibilizing agents were studied to investigate their effect on the quality of the interface between a phosphate glass fiber and a poly(lactic acid) (PLA) matrix. After application of the agents via dip-coating, the fibers were Soxhlet extracted to remove any unreacted compatibilizer. To assess the interface quality, single fiber tensile tests of treated fibers and interfacial shear strengths (IFSS) of single fiber composites (SFC) were assessed. Of the agents tested, Glycerol-2-phosphate disodium pentahydrate (GP) and low molecular weight PLA with a sodium salt terminal group (PLA-Na) showed the highest IFSS values, which were significantly higher than those of the control. Oligomeric PLA with a carboxylic acid end group and alendronate sodium trihydrate also showed an improvement over the control fibers. The hydrolytic degradation of these single fiber composites was studied over 7 days in water at 37 °C and a significant decrease in IFSS was observed in all cases, with the treated samples dropping to the level of the control. TGA and XPS analysis of the sized fibers showed that GP and PLA-Na had been applied successfully to the fiber surface. © 2010 Wiley Periodicals, Inc