Commingled Fibers Research Articles

Influence of Carding and Pressing on Hygrothermal Properties and Fire Reaction of Hemp Fiber Nonwoven Mats

This article depicts the effect of carding and pressing on hygrothermal properties of hemp fibers nonwoven mats, trying to understand if their implementation can improve their behavior when employed as insulation materials in buildings. Hemp fibers belonging to Cannabis Sativa species and coming from local area (Apulia - Italy) were examined, then samples of carded and pressed hemp fibers nonwoven mats were prepared. According to European standards, the thermal conductivity, the vapor permeability and the fire reaction of hemp fibers samples were measured. Results were compared to each other and with those of a commercial nonwoven mat made with hemp (90 wt. %) and synthetic fibers (10 wt. %), used as reference. We observed that carded and pressed hemp fibers were characterized by a lower thermal conductivity when compared to unprocessed hemp fibers, likely because the removing of wood elements. On the other hand, not processed hemp fibers show higher breathability when compared to carded and pressed ones, as well as with respect to the commercial nonwoven mat. Moreover, it was proved that the absence of synthetic commingled fibers in hemp fibers allows a better behavior in fire reaction. At last, the improvement in terms of insulation properties of a hollow brick when filled with hemp fibers was verified, by comparing the thermal conductivities of an empty and a filled hollow brick; as expected, the filled hollow brick shows a lower thermal conductivity, underlining the effectiveness of hemp fibers as insulation material.

Investigation about the Effect of Manufacturing Parameters on the Mechanical Behaviour of Natural Fibre Nonwovens Reinforced Thermoplastic Composites.

To date, nonwoven fabrics made with natural fibres and thermoplastic commingled fibres have been extensively used in the composite industry for a wide variety of applications. This paper presents an innovative study about the effect of the manufacturing parameters on the mechanical behaviour of flax/PP nonwoven reinforced composites. The mechanical properties of nonwoven fabric reinforced composites are related directly to the ones of dry nonwoven reinforcements, which depend strongly on the nonwoven manufacturing parameters, such as the needle-punching and areal densities. Consequently, the influence of these manufacturing parameters will be analysed through the tensile and flexural properties. The results demonstrated that the more areal density the nonwoven fabric has, the more the mechanical behaviour can be tested for composites. By contrast, it has a complex influence on needle-punching density on the load-strain and bending behaviours at the composite scale.

Mechanical behavior of flax/polypropylene commingled nonwoven at dry scale: Influence of process parameters

Currently, nonwoven fabrics made with natural and thermoplastic commingled fibers have been extensively used in the composite industry due to their light weight and low processing and material costs. As two key parameters in the manufacturing of nonwoven fabrics, the needle-punching and material surface densities influence strongly the mechanical properties of nonwoven fabrics and their reinforced composite parts. Compared to most studies focused on the composite stage, the present experimental investigation is performed at the dry fabric stage, and the influence of the needle-punching and material surface densities on the mechanical behavior of nonwoven fabrics will be analyzed through tensile and bending tests. The results show that increasing the material surface of the nonwoven fabric leads to a better mechanical behavior, but that such variations do not modify the phenomenon of anisotropy of nonwoven fabrics. By contrast, increasing the needle-punching density can strengthen generally the homogeneity of nonwoven fabrics.

The increase of sustainability in cylinder manufacturing

To satisfy the needs of a demanding and competitive market, Amtrol-Alfa decided to allocate its resources in a new innovative composite cylinder. The CoMet cylinder consists of a thin steel inner liner, wrapped in a commingled glass and polypropylene fibre inside a plastic jacket, which exceeded our expectations. Safety and environment are on the top of Amtrol-Alfa’s priorities. As such, the manufacturing of the CoMet cylinder has no dangerous emissions to the environment, in comparison with thermoset traditional processes, and uses inert products such as PP and HDPE. Regarding recyclability, the steel can be reprocessed, the commingled fibres can be chopped and used in injection processes, including the HDPE exterior jacket that can also be chopped and re-injected. The use of only recyclable products contributes to a better environment. The design was thoroughly studied, so that the handling is less aggressive to the costumer. The cylinder exterior is also very important, not only because the new design may look more ergonomic and elegant, but also because it is cleaner and safer. CoMet lightweight cylinder integrates in one cylinder, the Past and the Future, the Proven and the Innovation, in an elegant compromise.

Finite Element Modelling of Thermoplastic Matrix Composite Gas Cylinders

Continuous glass/polypropylene (GF/PP) commingled fiber tapes were employed to produce wrapped pressure gas vessels for domestic applications by using filament winding. The vessel structural-wall was built using a hybrid solution consisting in a very thin steel liner over wrapped by the filament wounded GF/PP commingled fiber tape layers. FEM analysis was used to evaluate if the composite gas pressure vessel based on the hybrid solution (steel liner + glass fiber reinforced thermoplastic) is capable to withstand the following pressure requirements: the metallic liner, alone, a minimum burst pressure of 4MPa and whole hybrid composite vessel minima internal test and burst pressures of 3 MPa and 6.75 MPa, respectively. Finally, gas pressure vessel prototypes manufactured in industrial cycle conditions were submitted to burst pressure tests to prove that they accomplish all European standard strength requirements.

High speed pultrusion of thermoplastic matrix composites

The main problem with using thermoplastic matrices for composites is the difficulty in impregnating the fibrous reinforcement with the high viscosity resin. This has led to the development of a number of different manufacturing techniques, which are used to fabricate thermoplastic matrix composites. One method is to provide the matrix in fibre form and intermingle, or co-weave, the polymer fibres with the reinforcing fibres. These commingled fibres should ideally be combined in the same strand, allowing a high degree of intimacy to be achieved and minimising the flow distance for impregnation. An alternative technique is to impregnate the reinforcing tow with polymer powder particles and then melt fuse the particles in place. This method, the dry powder impregnation technique, allows for the formation of resin bridges between adjacent fibres, and with the application of applied pressure, longitudinal resin flow takes place. This differs from the transverse impregnation which occurs with the commingled fibres.These two consolidation mechanisms have been characterised and modelled using compression moulding techniques on commingled and powder towpregs, and the results of these experiments have been applied to the on-line consolidation which occurs during pultrusion processing. Successful correlation was achieved between the experimental results and the models with commingled polypropylene/glass fibres and dry powder-impregnated PA12/glass fibre-reinforced towpregs. The models then enable users to produce well-impregnated continuously reinforced composites of minimal void content at high line speeds, those reported in this work are speeds up to 10 m/min. With more powerful processing equipment, even higher line speeds could be achieved, demonstrating the potential cost effectiveness of pultruded thermoplastic composites.

Compressive Strengths of Commingled Fiber Composite Systems

The idea of fiber commingling is proposed to increase compressive strengths and the effect of fiber commingling is evaluated by considering two different failure models, buckling failure and shear failure. Micro-buckling failure theory is extended to account for the nonlinear effects of the fiber and matrix by using Ramberg-Osgood stress-strain relations and the tangential modulus concept. In the case of shear failure, a more appropriate method to estimate the shear strength of each component is proposed. The effect of fiber commingling can be estimated from the controlling mode.

Development and evaluation of surface treatments to enhance the fiber‐matrix adhesion in PAN‐based carbon fiber/liquid crystal polymer composites. Part I: Coupling agent and amine surface treatments

AbstractSeveral surface treatments, using both commercially available coupling agents and reagents containing multiple amines, were applied to commingled continuous as‐received AS4 carbon reinforcing fiber/liquid crystal polymer (LCP) matrix fibers. Unidirectional composites (normally 60 vol% carbon fiber) were prepared from as‐received and treated commingled fibers and characterized. To estimate the effect the effect of the treatments on fiber‐matrix adhesion, short beam shear (SBS) tests were conducted, the failure surfaces were examined, and spectroscopic studies wee performed. The mean SBS strength of the as‐received unidirectional AS4 carbon fiber/LCP matrix composite system was 49 MPa. The best coupling agent and amine treatments yielded increases in composite shear strength of ∼ 10 to 20%, relative to the as‐received AS4/LCP system. For the amine treatments, ESCA and FTIR analyses suggested of both the carbon and LCP fibers may have caused the increased adhesion. Moreover, SEM analysis of the failure surfaces of SBS specimens from composites prepared with the treated fibers may have caused the increased adhesion. Moreover, SEM analysis of the failure surfaces of SBS specimens from composites prepared with the treated fibers (both with coupling agents and amines) showed that strong fiber‐matrix adhesion was present. That is, failure occurred in the LCP matrix material.