Direct Forming of All-Polypropylene Composites Products from Fabrics made of Co-Extruded Tapes

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.     

Low velocity impact performance of recyclable all-polypropylene composites

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 tapes. This paper investigates the impact resistance of these all-PP composites, and the relationship between penetrative and non-penetrative impact behaviour, and composite consolidation conditions. The response of all-PP composites to falling weight impact is reported together with a comparison to conventional commercial glass reinforced polypropylene composites. A model for energy absorption is proposed by comparison with previous studies based on interfacial and tensile failure of tapes and composites.     

The mechanical properties of woven tape all-polypropylene composites

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 and compares these mechanical properties to those of commercial alternatives.     

Dynamic mechanical thermal analysis of all-PP composites based on β and α polymorphic forms

All polypropylene (all-PP) composites were manufactured by exploiting the polymorphic forms of PP, in which alpha (α)-PP tapes worked as reinforcement and beta (β)-PP served as matrix. The mechanical performance of the composite was investigated in a range of frequencies and temperatures using dynamic mechanical thermal analysis (DMTA). The volume fractions of matrix and reinforcement were estimated using optical microscope images. Both the DMTA and the static flexural bending tests revealed that the α-PP tapes act as an effective reinforcement for the β-PP matrix. Time–temperature superposition (TTS) was applied to estimate the stiffness of the composites as a function of frequency (f = 10⁻⁹...10²³) in the form of a master curve. The Williams–Landel–Ferry (WLF) model described properly change in the experimental shift factors used to create the storage modulus versus frequency master curve. The activation energies for the α and β relaxations were also calculated by using the Arrhenius equation.     

All-poly(ethylene terephthalate) composites by film stacking of oriented tapes

Self-reinforced polymer or all-polymer composites have been developed to replace traditional fibre reinforced plastic (FRP) with good interfacial adhesion and enhanced recyclability. Poly(ethylene terephthalate) (PET) is one of the most attractive polymers to be used in these fully recyclable all-polymer composites, in terms of cost and properties. In this work, all-PET composites were prepared by film stacking of oriented PET tapes. A processing temperature window was determined by a series of tests on PET tapes and co-PET films, including DSC and T-peel tests. Tensile properties of PET tape, co-PET film and all-PET composites are reported and compared with a commercial co-extruded PURE^® polypropylene tape. The effect of compaction temperatures and pressures on tensile properties of all-PET composites was investigated to explore the optimum processing parameters for balancing good interfacial adhesion between tapes and residual tensile properties of PET tapes.     

Tensile mechanical and perforation impact behavior of all-PP composites containing random PP copolymer as matrix and stretched PP homopolymer as reinforcement: Effect of β nucleation of the matrix

All polypropylene (all-PP) composites were manufactured by exploiting the polymorphic forms of PP, in which alpha (α)-PP homopolymer tapes worked as reinforcement and β-nucleated random PP copolymer (β-rPP) as matrix. Both unidirectional (UD) and cross-ply (CP) laminates were prepared by tape winding technology combined with a film stacking method followed by hot pressing. To study the efficacy of using β-rPP as matrix, all-PP composites were also prepared with α-PP tape as reinforcement and alpha random PP copolymer (α-rPP) as matrix and their properties were compared. The mechanical performance of the composites was investigated by dynamic mechanical thermal analysis (DMTA), static flexure and dynamic impact tests. The volume fractions of the reinforcement and the void content were estimated by using optical microscope images. Both the DMTA and the static flexural bending tests revealed that the α-PP tape acted as a more effective reinforcement for the β-rPP matrix than for the α-rPP, especially for all-PP composites of UD lay-up. The perforation impact properties were determined from instrumented falling weight impact (IFWI) tests, performed at room temperature. It was found that transcrystalline layer is responsible for the stress transfer from the β-rPP matrix to the α-PP reinforcement.     

Environmental issues for polymer matrix composites and structural adhesives

 The U.S. Department of Defense (DoD) has been utilizing polymer matrix composite (PMC) and structural adhesive materials in military equipment for over 20 years. However, the volume of PMCs in fielded systems has remained relatively low. Currently, however, the DoD has established strategic goals that will necessitate the use of lightweight composites in order to meet performance requirements. Therefore, the volume of composites used in DoD systems is expected to see an unprecedented 100-fold increase over the next 30 years. As production volumes increase, the need to address environmental impact increases. The major contributions to environmental degradation from composites are generation of hazardous air pollutants (HAPs) and generation of hazardous (HW) and solid wastes. HAPs result primarily during the curing of the composite. HWs arise from expiration of stockpiled resin materials and from soiled support media used during manufacturing and clean up. Due to the wide range of applications and materials systems, as well as manufacturing and repair requirements, a family of environmentally benign solutions is needed to reduce and eliminate environmental impacts from PMC manufacturing. Solutions are proposed involving use of new technologies and materials to reduce pollutants from composite manufacturing. The technologies proposed include alternative curing of thermoset composites using electron beam (E-beam) irradiation and materials substitution employing thermoplastics processed using electromagnetic irradiation. Received: 25 April 2000 / Accepted: 25 July 2000     

Natural Fibre Mat Thermoplastic Products from a Processor's Point of View

Natural fibres have significant advantages over glass, as an alternative fibre reinforcement material. Natural fibres are more environmentally friendly, healthier and safer, and cause less abrasive wear of processing equipment. On the other hand, their mechanical properties show a large scatter, and are at best equivalent to glass (natural fibres, however, have a lower density). Further disadvantages of the current natural fibre reinforced materials are their moisture sensitivity – which makes them prone to swelling and rotting – their smell and their current cost level.Experiments with the application of Natural Fibre Mat Thermoplastics (NMT) on current automotive products proved the disadvantages. On the other hand it yielded several new research themes concerning property limits and gave insight in the area's where to optimize in order to get a broad application of natural fibre reinforced plastic products.Looking towards the long term, other alternatives, like bio-composites or all-PP composites should be further explored.     

Accelerated weathering of fire-retarded wood–polypropylene composites

In this study, the influence of fire retardants, namely aluminum trihydrate, zinc borate, melamine, graphite, titanium dioxide on the durability of polypropylene-based co-extruded wood–plastic composites is studied. The composites underwent accelerated weathering under a xenon-arc lamp source during 1000 h. FTIR analysis of the composite surface revealed a degradation process which was accompanied by chemical changes, including vinyl-like and carbonyl groups accumulation; fire retardants did not influence the photo-oxidation mechanism of the composite. Fire retardant-loaded samples had smaller color change compared to the unfilled one. The tensile properties of all composites declined after the weathering. Significant changes in the surface morphology of the weathered composites were observed with a scan electron microscope.     

Development of Flax Fibre based Textile Reinforcements for Composite Applications

Most developments in the area of natural fibre reinforced composites have focused on random discontinuous fibre composite systems. The development of continuous fibre reinforced composites is, however, essential for manufacturing materials, which can be used in load-bearing/structural applications. The current work aims to develop high-performance natural fibre composite systems for structural applications using continuous textile reinforcements like UD-tapes or woven fabrics. One of the main problems in this case is the optimisation of the yarn to be used to manufacture the textile reinforcement. Low twisted yarns display a very low strength when tested dry in air and therefore they cannot be used in processes such as pultrusion or textile manufacturing routes. On the other hand, by increasing the level of twist, a degradation of the mechanical properties is observed in impregnated yarns (e.g., unidirectional composites) similar to off-axis composites. Therefore, an optimum twist should be used to balance processability and mechanical properties. Subsequently, different types of fabrics (i.e., biaxial plain weaves, unidirectional fabrics and non-crimp fabrics) were produced and evaluated as reinforcement in composites manufactured by well established manufacturing techniques such as hand lay-up, vacuum infusion, pultrusion and resin transfer moulding (RTM). Clearly, as expected, the developed materials cannot directly compete in terms of strength with glass fibre composites. However, they are clearly able to compete with these materials in terms of stiffness, especially if the low density of flax is taken into account. Their properties are however very favourable when compared with non-woven glass composites.     

Design and manufacture of all-PP sandwich panels based on co-extruded polypropylene tapes

This paper describes the creation of polypropylene sandwich panels, based on all-polypropylene (all-PP) composite laminates combined with a polypropylene based honeycomb or foam core. These all-PP composite laminates are based on high modulus polypropylene tape reinforcing a polypropylene matrix. Sandwich panels containing these all-PP composite laminate faces are compared with sandwich panels containing conventional glass fibre reinforced polypropylene laminate faces, and the mechanical properties, failure modes, and design requirements of these different materials are discussed.     

钛基复合材料及其制备技术研究进展

综述了钛基复合材料及其制备技术,重点介绍了纤维增强钛基复合材料(FTMCs)和颗粒增强钛基复合材料(PTMCs)的制备技术,分析了各种制备技术的优缺点.研究表明:纤维涂层法具有纤维分布均匀,纤维与界面反应小,复合材料性能优异等优点,是一种很有前景的FTMCs的制备技术.原位合成工艺制备的PTMCs避免了界面反应,界面清洁、结合强度高,可以明显提高PTMCs的力学性能.     

Research progress of ceramic matrix composite parts based on additive manufacturing technology

ABSTRACT

Ceramic matrix composites (CMCs) are materials that can be engineered for high-temperature applications in various fields including aerospace, marine, etc. It is very difficult to fabricate CMCs using traditional moulding methods due to their brittleness and high hardness. Additive manufacture (AM) technology, a digital manufacturing technology, provides multiple advantages over traditional manufacturing technologies, such as fabricating geometrically complex parts, mould-free fabrication, short development cycle, etc. In this paper, various AM technologies developed for CMCs are reviewed with emphasis on mechanisms of manufacturing, characteristics of production, and recent research progresses. With the springing up of innovative ideas and pioneering work, AM technology possesses unique forming capabilities in fabricating CMCs, demonstrating strong potentials in the application of CMCs in aerospace and other fields. However, there are still many challenges of CMCs fabricated by AM technologies, i.e. poor mechanical properties and geometric accuracies; lower reinforcement volume fraction than that of traditional manufacturing processes.     

High performance carbon-carbon composites

Carbon-carbon composites rank first among ceramic composite materials with a spectrum of properties and applications in various sectors. These composites are made of fibres in various directions and carbonaceous polymers and hydrocarbons as matrix precursors. Their density and properties depend on the type and volume fraction of reinforcement, matrix precursor used and end heat treatment temperature. Composites made with thermosetting resins as matrix precursors possess low densities (1.55–1.75g/cm³) and well-distributed microporosity whereas those made with pitch as the matrix precursor, after densification exhibit densities of 1.8–2.0g/cm³ with some mesopores, and those made by the CVD technique with hydrocarbon gases, possess intermediate densities and matrices with close porosities. The former (resin-based) composites exhibit high flexural strength, low toughness and low thermal conductivity, whereas the latter (pitch- and CVD-based) can be made with very high thermal conductivity (400–700 W/MK) in the fibre direction. Carbon-carbon composites are used in a variety of sectors requiring high mechanical properties at elevated temperatures, good frictional properties for brake pads in high speed vehicles or high thermal conductivity for thermal management applications. However, for extended life applications, these composites need to be protected against oxidation either through matrix modification with Si, Zr, Hf etc. or by multilayer oxidation protection coatings consisting of SiC, silica, zircon etc.     

Ultrasonic consolidation for embedding SMA fibres within aluminium matrices

For this paper, adaptive composites will be considered as structural materials for advanced aerospace applications which have the ability to measure and respond to external stimuli by adapting the structure accordingly, through embedded active or passive functional elements. The intention of this project was targeted at the fabrication of adaptive composites using a novel layered manufacturing technique called ultrasonic consolidation (UC). This paper details the initial study of this research to identify plastic deformation of the matrix material around shape memory alloy (SMA) fibres, and bond quality, based on the microscopic observation and mechanical test results obtained. The embedding method, considered during this study, has successfully produced laminate specimens, with full consolidation, within seconds, using low oscillation amplitude and low contact pressures (<300 kPa). This work will report on the identification of the bonding characteristics for these SMA fibres when embedded in aluminium alloy 3003 specimens.     

纤维丝束带复合材料的有效性能预测与实验测试

依据纤维丝束带复合材料的相关几何结构参数值和所确定的纤维丝束带特征体积单元（RVE）模型几何结构尺寸,以有限元软件MSC.Patran/Nastran为平台建立纤维丝束带复合材料RVE有限元模型并在模型中置入相应的制备缺陷。各类制备缺陷的置入均采用删除网格单元的方法,置入裂纹型制备缺陷时偏移裂纹两侧单元相对面以获得当前裂纹宽度,置入孔洞型制备缺陷时尽量模拟其真实形貌。根据复合材料力学关于材料各性能参数的定义和细观力学基本理论推导了有限元计算细观力学（FECM）方法预测复合材料有效弹性性能和有效热膨胀性能的过程。根据FECM方法预测了不含制备缺陷、含单一制备缺陷和含各类制备缺陷时的弹性常数和有效热膨胀系数。结果表明:各类制备缺陷的存在均会使弹性模量和剪切模量减小,泊松比和热膨胀系数可能增大也可能减小。通过与实验测试结果对比分析可知,数值预测结果普遍比实验测试结果偏大,但总体效果较为理想,最大相对误差为6.04%。      

A review on basalt fibre and its composites

In recent years, both industrial and academic world are focussing their attention toward the development of sustainable composites, reinforced with natural fibres. In particular, among the natural fibres (i.e. animal, vegetable or mineral) that can be used as reinforcement, the basalt ones represent the most interesting for their properties. The aim of this review is to illustrate the results of research on this topical subject. In the introduction, mechanical, thermal and chemical properties of basalt fibre have been reviewed. Moreover, its main manufacturing technologies have been described. Then, the effect of using this mineral fibre as reinforcement of different matrices as polymer (both thermoplastic and thermoset), metal and concrete has been presented. Furthermore, an overview on the application of this fibre in biodegradable matrix composites and in hybrid composites has been provided. Finally, the studies on the industrial applications of basalt fibre reinforced composites have been reviewed.     

Effects of Chopped Carbon Fiber on the Forming,Structure, and Mechanical Properties of CCF/SiC Composites Fabricated by Selective Laser Sintering and Reactive Melt Infiltration

Silicon carbide (SiC) composites are fabricated by selective laser sintering (SLS) combined with reactive melt infiltration (RMI) using SiC powder mixed with various contents (0–32 vol%) of chopped carbon fiber (CCF) as reinforcement phase and carbon source. The introduction of an appropriate amount of CCF can reduce the shrinkage and step effect caused by slicing, improving the forming quality of the CCF/SiC preforms after pyrolysis. Meanwhile, as a carbon resource, CCF can react with molten silicon to form the β-SiC, improving the mechanical properties of CCF/SiC composites. The result shows that the CCF/SiC powder shows excellent fluidity, and the angle of repose of the CCF/SiC powder is 32–40° when the proportion of CCF is less than 24 vol%. CCF/SiC preforms shrinkage is lower than 1.74% and 1.94% along the nonadditive and additive manufacturing directions, respectively. Compared without CCF, the bending strength and fracture toughness of the CCF/SiC composites with 8 vol% CCF improve from 137.9 MPa and 2.69 MPa m^1/2 to 177.1 MPa and 3.10 MPa m^1/2, respectively. This study is believed to provide a new strategy for additive manufacturing of high-performance CCF/SiC composites with high CCF content by SLS.     

碳纤维单丝带对酚醛树脂基复合材料力学性能的增强作用

将连续碳纤维束用空气梳分散成单丝状的长带, 经60 %硝酸进行表面氧化处理后用作酚醛树脂复合材料的增强材料。用红外光谱、扫描电镜等表征复合材料的微观结构, 通过力学性能测定发现, 与连续的碳纤维束增强相比, 单丝带增强复合材料的弯曲强度提高了1 倍, 层间剪切强度( ILSS) 提高了2 倍, 但冲击强度有所降低。结果表明, 碳纤维经过表面氧化和丝束分散的处理后, 能有效地提高其与复合材料中树脂基体的结合性能。      

Glass-reinforced composites based on novel oligoimide-epoxy resin system

A novel matrix resin system, viz. oligoimide-epoxy resin, has been developed to prepare glass-fibre-reinforced composites. Diaminodiphenylmethanebismaleimide-diaminodiphenylmethane (DDMBM-DDM) andp-phenylenebismaleimide-diaminodiphenylmethane (PBM-DDM) oligomers having more-NH₂ groups were prepared through Michael addition reaction. These oligoimides were used for curing commercial epoxy resin (i.e. diglycidyl ether of bisphenol A) at 120–140°C to fabricate crosslinked oligoimide-epoxy resin glass-fibre-reinforced composites without evolution of byproduct. The fabricated composites (i.e. laminates) were characterized by their chemical resistance and mechanical properties.