Novel cattail fiber composites: converting waste biomass into reinforcement for composites

Vacuum-assisted resin transfer molding (VARTM), used in manufacturing medium to large-sized composites for transportation industries, requires non-woven mats. While non-woven glass mats used in these applications are optimized for resin impregnation and properties, such optimized mats for natural fibers are not available. In the current research, cattail fibers were extracted from plants (18–30% yield) using alkali retting and non-woven cattail fiber mat was manufactured. The extracted fibers exhibited a normal distribution in diameter (davg. = 32.1 µm); the modulus and strength varied inversely with diameter, and their average values were 19.1 GPa and 172.3 MPa, respectively. The cattail fiber composites were manufactured using non-woven mats, Stypol polyester resin, VARTM pressure (101 kPa) and compression molding pressures (260 and 560 kPa) and tested. Out-of-plane permeability changed with the fiber volume fraction (Vf) of the mats, which was influenced by areal density, thickness, and fiber packing in the mat. The cattail fibers reinforced the Stypol resin significantly. The modulus and the strength increased with consolidation pressures due to the increase in Vf, with maximum values of 7.4 GPa and 48 MPa, respectively, demonstrating the utility of cattail fibers from waste biomass as reinforcements.

Quantifying the Porosity of Crystalline Rocks by In Situ and Laboratory Injection Methods

The porosity and pore geometry of rock samples from a coherent granodioritic rock body at the Grimsel Test Site in Switzerland was characterised by different methods using injection techniques. Results from in situ and laboratory techniques are compared by applying innovative in situ resin impregnation techniques as well as rock impregnation and mercury injection under laboratory conditions. In situ resin impregnation of the rock matrix shows an interconnected pore network throughout the rock body, consisting mainly of grain-boundary pores and solution pores in magmatic feldspar, providing an important reservoir for pore water and solutes, accessible by diffusion. Porosity and pore connectivity do not vary as a function of distance to brittle shear zones. In situ porosity was found to be about 0.3 vol.%, which is about half the porosity value that was determined based on rock samples in the laboratory. Samples that were dried and impregnated in the laboratory were affected by artefacts created since core recovery, and thus showed higher porosity values than samples impregnated under in situ conditions. The extrapolation of laboratory measurements to in situ conditions requires great care and may not be feasible in all cases.

Surface properties of poplar wood after heat treatment, resin impregnation, or both modifications

To investigate the surface properties of different modified poplar (Populus tomentosa Carr.) wood samples, the color, surface roughness, and wettability of untreated poplar wood (control) and poplar modified via heat treatment, resin impregnation, and impregnation combined heat treatment were analyzed and compared in this study. The impregnant used in the test was a modified urea-formaldehyde resin with a low molecular weight and low viscosity. The results showed that the lightness of the samples was sorted in order as follows: the control was lighter than the resin impregnated sample, which was lighter than the impregnation combined heat treatment sample, which was lighter than the heat treatment sample. The surface of the control samples was relatively smooth, while after the impregnation, heat, and impregnation combined heat treatments, the Ra and Rz values increased, which indicated increased surface roughness due to the modifications. Among them, the heat-treated samples had the roughest surface, and the surface roughness of the impregnation combined heat treated samples at 160 °C had no major difference from the resin impregnated sample. The wettability of the samples decreased after heat treatment and increased after impregnation combined heat treatment. It was concluded that after the modification treatments, the color of the wood became darker, and the surface roughness and hydrophobicity increased.

Mechanical Properties of Thermoplastic Composites Made of Commingled Carbon Fiber/Nylon Fiber

Commingled yarns consisting of thermoplastic nylon fibers and carbon fibers can be used to produce superior carbon fiber reinforced thermoplastics (CFRTP) by applying fiber spreading technology after commingling. In this study, we examined whether spread commingled carbon fiber/nylon fiber yarns could reduce the impregnation distance, as there are few reports on this. From this study, the following are revealed. The impregnation speed of the nylon resin on the carbon fiber was very fast, less than 1 min. As the molding time increased, the tensile strength and tensile fracture strain slightly decreased, and the nylon resin deteriorated. The effects of molding time on flexural strength, flexural modulus, and flexural fracture strain were negligible. From the cross-sectional observation conducted to confirm the impregnation state of the matrix resin, no voids were observed in the molded products, regardless of molding time or molding pressure, indicating that resin impregnation into the carbon fiber bundle of the spread commingled yarn fabric was completed at a molding pressure of 5 MPa and a molding time of 5 min.

EVALUATION OF EFFECT OF SURFACE MODIFICATION ON CORRELATION BETWEEN PERMEABILITY OF GLASS FIBER/RESIN AND CAPILLARY NUMBER

In this study, we experimentally evaluated the correlation between the microscopic resin flow and permeability of a glass cloth, which surface was modified by silane coupling agent. We focused on the capillary number, which is a parameter determining the microscopic resin impregnation behavior within and between fiber bundles. The capillary numbers were classified into different parameters based on their dependency on temperatures and pressures. First, we obtained the temperature condition for each resin, to make the ratio between resin viscosity and (surface tension ・contact angle), constant be Under these temperature conditions, the pressure conditions were determined to be the resin impregnation rate constant. The permeability was evaluated with three types of resins under three conditions of capillary numbers. As a result, the permeabilities of the different resin systems were approximately equal. Therefore, it was found that the macroscopic permeability was not significantly influenced by the capillary number representing microscopic resin flow.

Mechanical Properties of Thermoplastic Composites Made of Commingled Carbon Fiber / Nylon Fiber

Fiber-opening treatment of commingled yarns consisting of thermoplastic nylon fibers and carbon fibers could produce superior CFRTP, but few studies toward that end have been conducted. In this study, we investigated whether an open weave fabric consisting of commingled yarns made of carbon and nylon fibers could shorten the impregnation distance of resin to carbon fibers, and there are few reports on the design of fabrics by opening carbon fiber bundles consisting of commingled yarns. From this study, following are cleared. The impregnation speed of the nylon resin on the carbon fiber was very fast, less than 1 minute. As the molding time increased, the tensile strength and tensile fracture strain slightly decreased and the nylon resin deteriorated. The effects of molding time on flexural strength, flexural modulus, and flexural fracture strain were negligible. From the cross-sectional observation conducted to confirm the impregnation state of the matrix resin, no voids were observed in the molded products regardless of molding time or molding pressure, indicating that resin impregnation into the carbon fiber bundle of the open-fiber mixed yarn fabric was completed at a molding pressure of 5 MPa and a molding time of 5 min.

An Investigation on the Feasibility of Fabricating Composites Using Outdated Waste Carbon Fibers and Easily Disposable Polyolefin Resins

Outdated-waste-carbon-fiber-reinforced olefin composites (oCFOCs) were fabricated with easily disposable polyolefin resins, polypropylene (PP), high-density polyethylene (HDPE), and low-density polyethylene (LDPE), by compressive molding using a hot press. The flexural and impact strengths of the oCFOCs from each respective resin type and oCF content, ranging from 35 to 70 wt.%, were increased by the aging treatment (120 °C and 95% humidity under a pressure of 0.8 MPa) until an aging time of three days, due to improved resin impregnation. For the oCFOC with PP, the hydrogen bond between PP and developed C-O groups due to the aging treatment and the existing silane layer of oCF is considered to assist cohesion between the resin and oCF. In particular, PP and 45 wt.% oCF content were the most effective conditions for improving the oCFOCs’ mechanical properties, in addition to endowing the oCFOCs with good moldability and dimensional stability. Our results demonstrate that durable recycled composites can be manufactured using oCF and PP.