Journal of Reinforced Plastics and Composites

Biocomposites were prepared using epoxidized linseed oil and flax fibre reinforcements in different assemblies. Epoxidized linseed oil was cured by two different anhydrides to check how its thermomechanical properties can be influenced. As reinforcements, nonwoven mat, twill weave and quasi-unidirectional textile fabrics with two different yarn finenesses were used. Their reinforcing effect was determined using dynamic mechanical analysis in flexure. Dynamic mechanical analysis served to determine the glass transition temperature (T_g) also. Shape-memory properties were derived from quasi-unconstrained flexural tests performed near to the T_g of the epoxidized linseed oil and its biocomposites. Flax reinforcement reduced the T_g that was attributed to off-stoichiometry owing to chemical reaction between the hydroxyl groups of flax and anhydride hardener. The shape-memory parameters were moderate or low. They were affected by both textile content and type.

Out-of-autoclave processable fiber/resin systems have been gaining much attention due to the elimination of needing a costly autoclave large enough to hold the part to be cured. For large composite structures this can pose a challenge. However, for these fiber/resin systems to replace conventional autoclave fiber/resin systems for use on aerospace structures, the damage tolerance capabilities need to meet (or exceed) those of current autoclave fiber/resin systems. In this experimental study, compression-after-impact strengths of two commercially available out-of-autoclave fiber/resin systems are compared to compression-after-impact strengths of a conventional autoclave fiber/resin system used as a baseline in this study. compression-after-impact testing was chosen since this is the most common method to assess laminates damage tolerance capabilities. Three different levels of impact severity were chosen and information on damage size and morphology are assessed along with compression-after-impact strength values. The results show the two out-of-autoclave fiber/resin systems examined in this study have similar damage tolerance characteristics to the autoclave fiber/resin system used in this study.

Twelve identical concrete prisms were strengthened with Carbon Fibre-Reinforced Polymer (CFRP) laminate strips on two opposite faces and the laminates were anchored using the newly developed CFRP π-anchor. Prisms were tested in tension to investigate the effectiveness of the anchor to possibly delay delamination and/or to prevent the complete separation of the laminate from the prism. The salient feature of the anchor is its wide head to resist high interfacial shear stresses and its shanks that were inserted in predrilled holes to provide mechanical anchorage and to resist pull-out. The anchor doubled the tensile load-carrying capacity, effectively delayed delamination and prevented the CFRP laminate from full separation. Furthermore, the strengthened prisms experienced noticeable deformation.

Sisal fibers were pretreated by alkali and maleic anhydride, and then mixed with polypropylene to fabricate sisal fiber-reinforced composites by a self-made vane extruder based on elongational flow field. Maleic anhydride-grafted polypropylene was used as compatilizer to increase the fiber/matrix interactions. The influence of treatment on the fibers structure, the damage to fibers in processing, interfaces of composites and the mechanical properties of composites were investigated. It was observed that the surface of treated fibers was improved obviously compared with that of untreated fibers, which was believed to increase the adhesion between the fibers and matrix. However, the treated fibers were more likely to be damaged during processing. In comparison to unmodified system, the incorporation of treated fibers could significantly enhance the mechanical properties of composites, especially adding the compatilizer of maleic anhydride-grafted polypropylene. The flexural and impact strengths were maximum for the sisal fiber/polypropylene and maleic anhydride-grafted polypropylene composites, and its tensile strength was also improved significantly. The major contribution of this change should be that the morphology of fibers could be well preserved in elongational flow field, which based on the vane extruder showed a good application in fiber-reinforced composites.

Fiber-reinforced composites play an important role in enabling the industrial composites industry including automotive, pressure vessels etc. to meet ever increasingly aggressive fuel efficiency requirements. Modeling and analysis is often employed in composite development as a tool to achieve faster and more cost-effective solutions to both product and process designs. Thermal conductivity measurements play a critical role in enhancing the fidelity of these models, especially in scenarios involving non-isothermal processing. Accurate characterizations of anisotropic thermal conductivities that are typical of dry fibrous preforms are especially challenging because of their highly porous and complex structures. In this article, an inverse approach is developed to estimate the anisotropic thermal conductivities of a dry preform made of biaxial [0°/90°] stitched glass-fiber mats based on the measurements of thermal conductivities of cured epoxy-matrix composites. This method is found to not only yield more accurate results than direct preform measurements but also provide the capability to characterize preforms in multiple directions rather than only through-thickness direction. The estimated thermal conductivities are used in preform heating simulation that is validated against experiments.

In this study, the effect of compounding principles on the properties of Polymer Bonded Soft Magnetic Nanocomposites (PBSMNs) was discussed. The polymethylmethacrylate /Fe₃O₄ magnetic nanocomposites (Fe₃O₄: 30 wt%) were prepared by the in situ process based on the solution and spray drying method, as well as by the ex situ process based on the kneading machine. As reference, the process combining these two compounding principles was also carried out for the PBSMN preparation, named as in-between process. The morphology structures, thermal, mechanical and magnetic properties of the magnetic nanocomposites achieved with different compounding principles were characterized. The results show that compounding principles have significant influence on the properties of the magnetic polymer nanocomposites. In the end, their contributions to the power electronic applications were discussed as well.

This paper presents a multi-scale correlating model to simulate the elastic and failure behavior of two-dimensional tri-axial braided composites. Unlike the traditional information-passing multi-scale approaches, the present analytical model enables a two-way coupling of scales through a bottom-up homogenization procedure and a top-down decomposition procedure, based on the continuum mechanics and homogenization method. The main feature of this model is that it not only concurrently obtains the stress/strain fields in multiple scales but also allows the application of constituent-based failure criteria to reveal local failure mode, failure sequence and the resulting failure progression of the composites. Using the multi-scale correlating model, the stiffness and strength of a braided composite are predicted solely from its corresponding constituent properties and braid geometrical parameters, which can be easily obtained. The predicted failure events and the corresponding stiffness degradation are in good agreement with experimental data found in the literature. Parametric studies are also performed to examine the effect of various geometrical parameters such as braid angle, tow undulation and manufacturing-induced defects on the resulting mechanical properties. It is found that micro-structural imperfections play a role in the strength reduction, and the most detrimental factors are the defects of bias tow.

The effect of nanoclay content on the mechanism governing nanoclay dispersion was investigated through studying the interaction between nanoclay content and other factors. We hypothesized that at low nanoclay content, the dispersion was diffusion controlled; thus, increasing thermal diffusion and residence time, even when the shear intensity was compromised, were beneficial to nanoclay dispersion. At high nanoclay content, however, at which the process was found to be shear controlled, increasing shear intensity was essential to better dispersion, even when the thermal diffusion and residence time were sacrificed.

Construction sector is one of the largest markets for fibre reinforced polymers (FRPs) globally. FRP composites are used in a wide range of applications in construction ranging from rehabilitation of existing structures to the full-scale use for new projects because of the benefits they provide over conventional building materials. Such advantages include but not limited to lightness, high mechanical performance and possibility of production in any shape, ease of installation and lesser requirement for supporting structure, controlled anisotropy, high specific strength and specific stiffness. All these multifarious features of FRPs are knocking the doors for new avenues of myriad applications in the Construction Industry, but unfortunately polymeric composites are susceptible to heat and moisture when operating in changing environmental conditions dispelling the biggest myth of them being invincible. The heat response of FRPs is also a major issue of importance in dictating the fate of FRPs future acceptability and applicability. This paper thus attempts to review the specific areas of the current utilization trend of FRPs in the Construction Industry and draw their advantages to support the future applications in a variety of construction processes. It is also being attempted to juxtapose the applicability and the durability concerns of FRPs in a single literature for assessing the versatility and scope of FRPs, by shedding light on the past available studies on the related matter.