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This article describes the use of a novel lactone-layered double hydroxide polymer network (PN), derived from a poly(lactide-co-caprolactone) copolymer, as a controlled ion-release agent for artificial bone tissue regeneration. The osteogenic cell culture Saos-2 is used as a test culture to investigate the PN's performance as an extracellular ion-release agent. The compelling performance of this PN is demonstrated in both growth and osteogenic media compared with a control of cells grown on tissue culture plastic (TCP) without PN. Firstly, the PNs released concentration of magnesium ions over time ranging from 10 to 60 mM after 24 hr, depending on the PN sample. After incubation of Saos-2 with the PN, while no difference was seen in cell number, there was significant upregulation of bone-related gene expression at 14 days-~5fold increase in Bone Morphogenetic Protein 2, ~3fold increase in osteopontin and ~2fold increase in collagen Type I. In addition, normalized alkaline phosphatase activity was seen to significantly increase by ~2fold with PN presence. A ~4fold increase in collagen Type I protein expression (via Gomori Trichrome Stain) was observed with PN presence. In addition, a ~4fold increase in phosphate deposits (as seen with Von Kossa staining analysis) was seen with PN presence. It is found that this novel PN material has a significant potential for bone tissue regeneration.

A novel material and process was developed using fibre-reinforced powder-epoxy to produce unidirectional towpreg with a pilot-scale towpregging line, for cost-effective production of large composite structures for the renewable energy market, specifically for wind and tidal turbine blades. Electrostatic attraction was used to coat fibre tows with powder epoxy and either joule or radiant heating employed to heat and melt the polymer, followed by consolidation between rollers. Unidirectional carbon-fibre and basalt-fibre reinforced polymer laminates (UD-CFRP and UD-BFRP, respectively) were manufactured from the towpreg. Tensile test results showed that the towpregging process could be employed to achieve high performance UD-CFRP with 0° tensile properties that are similar or better than commercially-available UD-CFRP systems. The competitive advantages of the powder-epoxy towpreg system include lower cost, better overall manufacturing control for vacuum-bag-only manufacturing and the ability to co-cure parts together at a later stage. Mechanical test results showed some variation between two types of UD-BFRP, but the results compared well with published data on UD-BFRP and equivalent glass-fibre reinforced polymer (GFRP) systems. Finally, the influence of hygrothermal ageing due to water immersion on the tensile properties of the materials was investigated, with tests revealing that the water ageing effect was more severe in the case of UD-BFRP than for UD-CFRP.

This study aims to address barriers which remain to adoption of reactive thermoplastic resin transfer moulding in terms of knowledge and equipment. Glass fibre reinforced polyamide 6 composites with ~52% fibre volume fraction and ~1% voids were produced within 5 min using thermoplastic resin transfer moulding by injection of low viscosity monomer precursors and in-situ polymerisation. Unidirectional laminates were produced using injection pressures of around 10% of those required to achieve the same fibre volume fraction and degree of wet-out using a typical thermoset RTM resin, negating the need for expensive equipment. The equipment and process employed are described in detail and the quality and properties of the polymer matrix and composite laminates were characterised extensively in terms of chemical, thermo-morphological and mechanical properties. The paper demonstrates the high quality parts that can be achieved by accurately controlling some of the most important parameters. Keywords: Thermoplastic resin, Mechanical properties, Resin transfer moulding, In-situ polymerisation

Carbon fibres with three different sizing agents were used to manufacture unidirectional composites based on a powder epoxy resin. Powder epoxy processing was investigated as a route for fast, cost-effective manufacturing of out-of-autoclave composites compared to more time-consuming vacuum infusion technologies. In this work, a heat-activated epoxy powder was used as a resin system in low-cost vacuum-bag-only prepregs for thick composite parts that are required in the renewable energy industry (e.g. wind turbine blade roots). The importance of interfacial bonding between fibres and the matrix is shown and the impact on the ultimate mechanical performance of the manufactured composites demonstrated. The surface characteristics of the sizing on the carbon fibres were investigated using atomic force microscopy (AFM) and Raman spectroscopy. Results showed that the amount of sizing on the fibres' surfaces was inextricably linked with surface roughness and coverage. This in turn influenced the mechanical and chemical interlocking phenomena occurring at the fibre/matrix interface. The composites’ mechanical performance was evaluated using tensile, flexural and interlaminar fracture toughness tests. Fractographic analysis using optical and scanning electron microscopy (SEM) was likewise employed to analyse the fracture surfaces of the tested/failed composites. Interlaminar fracture toughness testing (DCB Mode-I) revealed that the interfacial adhesion differences could alter the fracture resistance of the composites, hence emphasizing the importance of the interfacial bonding strength between the polymer matrix and the carbon fibres.

In a fibre-reinforced polymer matrix composite (PMC), the function of the fibre is to bear the applied load that is transferred via shear stresses through the fibre-matrix interface from the polymer matrix. The fibre absorbs stress by progressively fragmenting along its axis until a critical fibre fragment length is realized. After this no further fragmentation is possible, the fibre is said to be “saturated” in stress, and it provides no strengthening upon further deformation. A critical and intrinsic material property of the composite that determines the failure of the fibre is the interfacial shear strength (IFSSh) between matrix and fibre. This review presents the multi-fibre fragmentation technique (MFFT) and Laser Raman Spectroscopy (LRS) which are used for fibre-matrix interface testing. The limitations of MFFT are summarised and ideas for improvement are proposed. The key findings of this review are: (1) MFFT equipment and protocols vary considerably and require standardisation. (2) Existing models for stress transfer between fibres rely on geometrical models that do not capture the material properties or the constitutive models of the transmitting matrix. Comprehensive constitutive matrix stress transfer models are needed. Current MFFT models do not incorporate terms for matrix vibration as a function of fibre fracture shock. It is clear that more work can also be done to characterize microcomposite systems in compression, at various angles to the fibre axis, and under various combinations of cyclic loading, but arguably such work should be pursued after the uniaxial tensile fibre fragmentation problem has been better understood.

This paper for the first time presents experimental results for fibre flow and void formation during 3D printing of short fibre reinforced thermoplastic composites by fused filament fabrication (FFF). Short carbon fibre T300 reinforced nylon-6 composite is selected as the printing material. X-ray micro-tomography (µCT) scans are performed on the raw filament, in-nozzle melted filament, extruded printing bead and on-bed printing bead to trace the through-process evolution of fibres and voids for the specific nozzle used therein. Qualitative visualisation of voids fraction and fibre orientation, length and fraction, as well as quantitative analysis are carried out using image processing techniques. The results show that the orientation and volume fraction of fibres vary with different internal geometry of the nozzle and fibre misalignment occurs in the on-bed printing bead because the relative motion between the nozzle and the print bed disturbs the flow field. Also the fibre length decreases slightly during the printing process due to the collision between fibre and nozzle wall when the melted materials pass the nozzle. For the void volume fraction, most voids are generated when the melted filament is extruded from the nozzle, and porosity decreases in the on-bed printing bead. The reported experimental data of through-process evolution of fibre flow and void formation can also be used for benchmarking and/or validating computational models for 3D printing of short fibre reinforced polymer composites.

This paper describes the conversion of a layered anionic initiator (carbonate-intercalated layered double hydroxide, (LDH-carbonate)) into a self-assembled resin-embedded network during the in-situ polymerization of one or more lactone monomers using the LDH-carbonate as the sole initiator. Uniquely in this paper, no long-chain acid intercalant is present in the LDH-carbonate to act as an additional initiator species, and this is the first known report of a copolymerisation of these lactones using LDH as an initiator. The formation of a network is in marked contrast to the behavior of most in-situ polymerisations using layered species, where the latter retains its layered structure at the molecular level and is either intercalated or exfoliated to form a nanocomposite. The molecular disintegration of the LDH sheets is unusual. Nine new insoluble materials (scaffolds) are isolated from various l , d -lactide & e-caprolactone (LC) and l , d -lactide & δ-valerolactone (LV) copolymer hybrids. The latter hybrids are polymerised using the LDH-carbonate as initiator at 150 °C for 24 h without using conventional metal catalysts. Each insoluble phase is isolated from each primary hybrid product using dichloromethane (DCM) to selectively dissolve the soluble polymer phase. X-ray diffraction (XRD) is used to verify the morphology of the insoluble phases. This demonstrates that the molecular sheets of the LDH-carbonate are fully dismantled during the polymerization. Porous, network morphology is established for some of the insoluble phase structures using scanning electron microscopy (SEM). This indicates potential suitability of these self-assembled insoluble phase materials as bioscaffolds for artificial cell growth. Nuclear magnetic resonance spectrometry (NMR) was used to determine the ratio of ester to acidic carbonyls in the insoluble phase. Energy Dispersive X-ray spectroscopy (EDX) was also used to determine the ratio of magnesium to aluminium in the insoluble phases.

This paper presents a comprehensive experimental study of impact damagedetection for carbon fibre-reinforced polymer (CFRP) composites using anelectromagnetic (EM) sensor with coupled spiral inductors (CSI). Tworepresentative types of damage are detected and evaluated, i.e., barely visibleimpact damage (BVID) and delamination. A multi-frequency inspection isperformed, where the resultant images indicate the potential of the CSI sensor inthe characterisation of damage extent. The accuracy and efficiency of the CSIsensor are compared with the open-ended waveguide imaging, near-fieldmicrowave microscopy, microwave time-domain reflectometry, thecomplementary split-ring resonator and ultrasonic scanning. Applications andlimitations of these non-destructive testing (NDT) methods for identifying impactdamage are discussed. There is a free edge effect on the electromagnetic signal,which is illustrated for the first time with the proposed EM technique. Detectionof the air gap produced by inserting a thin piece into a machined subsurfacegroove is carried out. It is found that the developed CSI sensor is able toaccurately resolve the location and extent of the air gap. The experimentalresults demonstrate that the sensor could offer an alternative relatively low costmethod that can be fully automated for structural monitoring of aircraft andother composite structures.

A hardware-in-the-loop simulation has been developed to eval uate the performance of active missiles from prelaunch to inter cept. The facility is used for system integration, design verifica tion, preflight and postflight analysis, and demonstrations of systems performance. A CDC Cyber 175 general-purpose computer interfaced with an Applied Dynamics International AD-10 multiprocessor solves the six-degree-of freedom simulation in real time. The simulation includes the target model, the missile model, and relative motion. The Cyber 175 also drives the model of the RF environment through a Hewlett Packard 1000 computer. The model of the RF environment provides the necessary phase and amplitude control to reproduce a 10-point glint model. The facility also can receive an active transmission and can supply four independent returns separated in range, angle, and velocity. The simulation has not yet undergone a formal validation program, but the facility results have been compared to an all- mathematical simulation of an active missile. Initial comparisons with flight results support the credibility of the facility.