Bending Properties Of Composites Research Articles

Recycling effects on the bending, rheological, and structural properties of glass fiber-reinforced isotactic polypropylene composites

In the present work, a combination of virgin polypropylene and E-glass fiber was subjected to ten (10) reprocessing cycles via extrusion and compression molding techniques to mimic recycling and its impacts on the bending properties of the composites. The samples were characterized using Fourier transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), scanning electron microscopy (SEM), and melt flow index (MFI). The results revealed a gradual depreciation in flexural properties after each reprocessing cycle. The XRD analysis indicated a substantial reduction of peak intensities, degrees of crystallinities, and average crystallite sizes, explaining the lowered flexural properties in addition to a possible reduction in glass fiber lengths (fiber attrition). Melt-processing behavior shows a progressive increase of MFI from 7 to 19.16 g/10 min, confirming the probable damage in molecular weight and loss of complex viscosity. Chemical and structural analysis showed no alteration in the polypropylene major functional groups. It is concluded that the reductions in molecular weight and composites’ properties occurred due to chain scission from recycling effects; hence, glass fiber-reinforced polypropylene composites can be recycled only three (3) times unless it is refreshed by the addition of virgin parts to compensate for the lost property.

Research on Mechanical Properties of Domestic T700S Carbon Fibers

Two types of domestic T700S carbon fibers (CF1 and CF2) were investigated in three batches to find out their mechanical properties, including tensile properties of multifilament, tensile and bending properties of composites. The results showed that the mechanical properties of domestic T700S CF are comparable to those of Toray T700S CF with a small discrete coefficient obtained from experiments for the three batches of CF, and that the unidirectional CF2 composite laminates has the biggest tensile strength discrete coefficient, 3.84%. The difference of properties between the two types of fiber composites was analyzed using the optical contact angle measuring device. It was found that CF2 and resin have better wettability. The two types of carbon fibers were examined by the Ø150 mm standard pressure vessel. Temperature (high temperature, low temperature, and temperature impact) tests and aging tests revealed that: high temperature, low temperature, and temperature impact have little effect on the characteristic index of the pressure vessel; after 800h aging, the characteristic index of the pressure vessel decreased by 15.2%.

Influences of wrinkles induced by tows’ offset in automated fiber placement on the bending properties of composites

This paper studies the influence of wrinkles caused by tows’ offset on the bending performance of composite laminates during Automated Fiber Placement (AFP) manufacturing. In this paper, the different distances of tows’ offset are set to prepare laminates containing various wrinkles and obtain the characteristics of different wrinkles through the feature recognition algorithm. Then a three-point bending test is conducted to investigate the influences of different wrinkles on the flexural strength and failure mode of laminates. The results indicate that wrinkle defects reduce the flexural strength of the laminate by about 12% to 15%, and the flexural strength is positively correlated with the wrinkle smoothness S. As the wrinkles increase, the failure mode of the laminate gradually changes from local collapse under the punch to instantaneous shear failure in the wrinkle area, and the degree of warping and delamination increases. Therefore, avoiding wrinkle defects can effectively maintain flexural strength and reduce the extent of warping and delamination.

An experimental investigation for the temperature effect on the bending properties of multiaxial warp-knitted composite

An experimental study of bending properties of composites reinforced with triaxial and quadaxial warp-knitted glass fabrics was carried out in the 0°, 45°, and 90° directions at −30°C, 0°C, 20°C, and 40°C, respectively. The relationships between the stress–strain curves, bending strength, bending modulus, and temperature were obtained. The failure mechanisms at different temperatures were also analyzed based on the fracture morphologies and scanning electron microscope (SEM) images. The results indicated that the bending properties decrease slightly with the increase in temperature from −30°C to 20°C and decrease dramatically from 20°C to 40°C. The ultimate bending strength of triaxial and quadaxial warp-knitted composites decreases approximately 31.34% and 34.29%, respectively. In particular, the relationships between bending strength and temperature were also obtained by nonlinear fitting with the experimental data, which could be used to predict the bending behavior at different temperatures.

Thermal Cyclic Resistance Polyester Resin Composites Reinforce Fiber Nut Shell

The purpose of study is to determine the effect of fiber length and thermal cyclic of the bending strength of polyester resin composite reinforced by fibers nut shell. The materials used in this study is a nut shell fibers with fiber length of 1 cm, 2 cm and 3 cm and polyester resin with composition 70-30%wt. Fiber nut shell treated soaking in NaOH 30% for 30 minutes, then rinse with clean water so that the fiber free of alkali and then dried. Furthermore, the composite is heated in an oven to a temperature of 100°C for 1 hour and then cooled in the open with a variety of thermal cyclic 30, 40, and 50 times. Bending properties of composites known through the testing process using a three-point bending test equipment universal testing machine. The test results show that the bending strength bending highest in fiber length of 3 cm with 30 treatment cycles of thermal to the value of 53.325 MPa, while the lowest occurred in bending strength fiber length of 1 cm with no cycles of thermal treatment to the value of 30.675 MPa.

Influence of Yarn-Reduction Technique on Bending Properties of Tapered 3D Braided Composites

The influence of distance between yarn-reduction cross-sections on bending properties of double-times yarn-reduction composites was investigated in this paper. Tapered 3D braided composites were prepared with the distances between two yarn-reduction cross-sections ranging from 1 pitch to 5 pitches. Bending properties in the center of the two yarn-reduction cross-sections were tested and the fracture morphologies were compared. Results show that damages mainly occur near the second yarn-reduction cross-section when the distances are 1 pitch to 3 pitches. However, obvious damages are found in the center of the two yarn-reduction cross-sections when the distances are 4 and 5 pitches. As the distances between yarn-reduction cross-sections increase from 1 pitch to 4 pitches, bending properties of the composites increase, too. For composites with 5 pitches distance, their bending properties are nearly the same as those of the composites with 4 pitches distance.

Safety evaluation of composites with a wrinkled fabric preform under bending

Wrinkled fabrics in the preform exert significant influence on the qualities of resin transfer molded composites (RTMCs). The bending properties of composites with wrinkled fabrics were studied using several wrinkled models with different wrinkled lengths and numbers of fabric plies, as well as three different matrices and four different loading rates. It was found that the measured bending properties with a strong matrix are less sensitive to wrinkling than those with a weak matrix. The bending moduli of a composite with wrinkled fabric preform are larger than those of a composite with a non-wrinkled fabric preform even under the same effective fiber volume fraction (\( V_{\rm f}^{\prime} \)) when the composite is loaded in the middle of the wrinkled region. The bending strengths of the wrinkled models are lower in low \( V_{\rm f}^{\prime} \) and higher in high \( V_{\rm f}^{\prime} \) than those of a perfect sample. Also, the bending strengths indicate two failure mechanisms as a function of the ratio of the wrinkled length to the span length (L W/L). Based on the experimental data, safe strength conditions of the wrinkled models that are better than those of a perfect sample are suggested under three-point bending.

Bending properties of epoxy resin matrix composites filled with Ni–Mn–Ga ferromagnetic shape memory alloy powders

Two types of epoxy resin matrix composites filled with Ni–Mn–Ga ferromagnetic shape memory alloy powders, with and without magnetic field during curing, were prepared, aiming to create anisotropic and isotropic alignments of the Ni–Mn–Ga particles. The bending properties of the composites are found to be significantly influenced by the distribution of Ni–Mn–Ga particles in the epoxy matrix. The composites without magnetic field during curing exhibit larger bending strength and fracture strain than the composites with magnetic field during curing. The fractography reveals that the Ni–Mn–Ga particle chains formed in the composites with magnetic field during curing facilitate the initiation and propagation of cracks, thus weakening the bending properties.

The Influence of Structure of Hybrid Yarns Glass/PA6 on Mechanical Properties of Composites

The fabrication process of thermoplastic composites using hybrid fabrics composed of yarns made of glass and PA6 fibres as prepregs is presented. The influence of the structure of hybrid yarns produced using commingled, texturising, twisting and friction spinning technology on the mechanical properties of composites is discussed. The results of the investigation indicate that the best tensile and bending properties of composites were achieved using fabrics made from texturing yarns produced under optimal conditions. These optimal conditions should ensure the minimum destruction of filaments during the blending process.

Annealing effect in glass woven fabric composites, Part II. Bending properties

Effects of annealing on bending properties of composites reinforced with plain glass woven fabrics that were treated with different concentrations of silane coupling agent were investigated in this paper. Bending strength increased by annealing in the specimen treated with lower silane concentration. Higher annealing temperature in a range from 80°C to 150°C led to higher bending strength. Then, the fracture mode changed from a micro-crack type (low strength type) to a branched matrix crack type (high strength type) by annealing.