Effect of sizing agent on interfacial properties of carbon fiber-reinforced PMMA composite

The surface treatment of carbon fibers (CFs) was carried out using a self-synthesized sizing agent. The effects of sizing agent on the surface of CFs and the interface properties of CF/polymethyl methacrylate (PMMA) composites were mainly studied. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and static contact angle were used to compare and study the CFs before and after the surface treatment, including surface morphology, surface chemical element composition, and wettability of the surface. The influence of sizing agent on the mechanical properties of CF/PMMA resin composite interface was investigated. The results show that after sizing treatment, the CF surface O/C value increased by 35.1% and the contact angles of CF and resin decreased by 16.2%. The interfacial shear strength and interlayer shear strength increased by 12.6%.

Dynamic mechanical behaviors of epoxy resin/hollow polymeric microsphere composite foams under forced non-resonance and forced resonance

Composite foams with 10–50 vol% hollow polymeric microspheres were prepared using bisphenol A epoxy resin and polyetheramine curing agent as the matrix. The results demonstrated that the density, hardness, and static mechanical properties of the epoxy resin/hollow polymer microsphere composite foams, as well as their dynamic mechanical properties under forced non-resonance, were similar to those of polymer/hollow glass microsphere composite foams. At 25°C and under 1–100 Hz forced resonance, the first-order and second-order resonance frequencies of the composite foams shifted to the low-frequency region as the volume fraction of hollow polymer microspheres increased. Meanwhile, the first-order and second-order loss factors of the as-prepared composite foams were improved by 41.7% and 103.3%, respectively, compared with the pure epoxy resin. Additionally, the first-order and second-order loss factors of the as-prepared composite foams reached a maximum at 40 vol% and 30 vol% hollow polymer microspheres, respectively. This research helps us to expand the application range of composite foam materials in damping research.

Influence of machining parameters on micro-motion platform displacement during grinding Al-Mg alloys workpiece assisted by two-dimensional low-frequency vibration

The main factors affecting the displacement of micro-motion platform during the grinding process are spindle speed, cutting force, and piezoelectric ceramic input voltage model. This article, using the orthogonal test method, found a set of machining parameters which lead to less displacement deviation between practical test and theoretic analysis. First of all, single-factor experiments were carried out to study how spindle speed, cutting force, and piezoelectric ceramic input voltage model affect the experimental results, and then the orthogonal test was conducted. The experimental datum shows that voltage model was the most influential factor, followed by spindle speed and cutting force. The optimum combination of grinding parameters was obtained as spindle speed of 800 r/min, cutting force of 18 N, and voltage model radius of 12 µm. At this time, the average unit error of displacement of micro-motion platform was 9.13%.

Tensile and fatigue properties of fiber-reinforced metal matrix composites Cf/5056Al

Fiber-reinforced metal matrix composites have mechanical properties highly dependent on directions, possessing high strength and fatigue resistance in fiber longitudinal direction achieved by weak interface bonding. However, the disadvantage of weak interface combination is the reduction of transversal performances. In this article, tensile and fatigue properties of carbon fiber-reinforced 5056 aluminum alloy matrix (Cf/5056Al) composite under the condition of medium-strength interface combination are carried out. The fatigue damage mechanisms of Cf/5056Al composite under tension–tension and tension–compression loads are not the same, but the fatigue life curves are close, which may be the result of the medium-strength interface combination.

Improving the mechanical properties of polypropylene composites with coconut shell particles

Conventional inorganic fillers are widely used as fillers for polymer-based composites. Though, their processing difficulties and cost have demanded the quest for credible alternatives of organic origin like coconut shell fillers. Dried shells of coconut were burnt, ground, and sifted to sizes of 63, 150, 300, and 425 µm. The ground coconut shell particles (CSP) were used as a filler to prepare polypropylene (PP) composites at filler contents of 0% to 40% via injection melt blending process to produce PP composite sheets. The effect of the filler particle size on the mechanical properties was investigated. The decrease in the size of filler (CSP) was found to improve the yield strength, tensile strength, tensile modulus, flexural strength, flexural modulus, and hardness of PP by 8.5 MPa, 15.75 MPa, 1.72 GPa, 7.5 MPa, 100 MPa, and 10.5 HR for 63 µm at 40%, respectively. However, the elongation at break and modulus of resilience of the PP composites were seen to increase with increase in the filler size. Scanning electron microscope analysis showed that fillers with 63 µm particle size had the best distribution and interaction with the PP matrix resulting in enhanced properties.

The research on precise forming technology of “λ” type composite skin

With the application of “ λ” type composite skin becoming more and more extensive and diversified, its precise forming technology is also widely concerned. This article mainly solves the quality problems of “ λ” type corner area, such as delamination dispersion and surface wrinkle, which exist in reality commonly in the manufacturing process. The prepreg is heated along the corner area of the tooling to solve the problem that prepreg is difficult to be compacted due to the large modulus of carbon fiber in “ λ” type corner area. Furthermore, two precompaction tests are creatively increased at 16 layers (middle layer) and 32 layers (last layer) for the thick structure, respectively, to ensure the compaction effect of the blank. In addition, combined with the characteristics of highly elastic rubber and carbon fiber-reinforced materials, a new type of soft mold structure with proper flexibility and good stiffness is proposed innovatively through the reasonable placement of carbon fiber-reinforced materials and the setting of exhaust holes according to the structure characteristics of “ λ” type root skin. Through further process verification, it is shown that the improved process has effectively solved the problems of wrinkles and internal delamination at the sharp corners of parts and realized zero-defect manufacturing of “ λ” type root skin for the first time.

Structure optimization of woven fabric composites for improvement of mechanical properties using a micromechanics model of woven fabric composites and a genetic algorithm

This research aims to optimize the mechanical properties of woven fabric composites, especially the elastic modulus. A micromechanics model of woven fabric composites was used to obtain the mechanical properties of the fiber composite, and a genetic algorithm (GA) was employed for the optimization tool. The structure of the fabric fiber was expressed using the width, thickness, and wave pattern of the fiber strands in the woven fabric composites. In the GA, the chromosome string consisted of the thickness and width of the fill and warp strands, and the objective function was determined to maximize the elastic modulus of the composite. Numerical analysis showed that the longitudinal mechanical properties of the strands contributed significantly to the overall elastic modulus of the composites because the longitudinal property was notably larger than the transverse property. Therefore, to improve the in-plane elastic modulus, the resulting geometry of the composites possessed large volumes of related strands with large cross-sectional areas and small strand waviness. However, the numerical results of the out-of-plane elastic modulus generated large strand waviness, which contributed to the fiber alignment in the out-of-plane direction. The findings of this research are expected to be an excellent resource for the structural design of woven fabric composites.

Facile growth of high transmittance ZnO micro-rod clusters on indium tin oxide by a wet-chemical synthesis method

A simple wet-chemical synthesis method was developed to fabricate Zinc oxide micro-rod clusters. The synthesis process involved the rapid dilution of a zinc-bearing alkaline solution at 150°C in a convection oven on indium tin oxide (ITO) substrates. The synthesis was carried out by immersing an unseeded ITO substrate in a mixture of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and hexamethylenetetramine ((CH2)6N4) aqueous solution. The obtained sample was annealed at 400°C for 2 h. The structural, morphological and optical properties of the synthesized ZnO microstructures were investigated by X-ray diffraction, scanning electron microscopy and ultraviolet-visible spectroscopy, respectively. The ZnO rod clusters are hexagonal phase of the wurtzite structure. The crystal grain sizes of the films were found to be 72.6, 84.3 and 66.3 nm for the (100), (002) and (101) crystal planes, respectively. The optical bandgap of the ZnO was determined to be 3.147 eV.

Location effects on bend-twist coupling modes characteristic of the laminate plates

In this paper, the effects of coupling location on the properties of bending-twist modes are proposed. The static test and modal analysis of the composite plates are investigated. Initial coupling effects are first obtained from the static test of the plates. The frequencies, nodal lines, and the mode shapes are then studied experimentally and numerically. A new method is proposed to quantitatively describe the bending-twist coupling performance of laminates using modal assurance criterion. The results show that the coupling location in the middle coupled plates show good coupling effects at lower order vibrations. These results also show that the effect of coupling stiffness. The conclusions can be considered as a reference to analyze the coupling phenomenon of large composite wind turbine blades.

Investigation of deformation behavior of PETG-FDM-printed metamaterials with pantographic substructures based on different slicing strategies

Based on the progress and advances of additive manufacturing technologies, design and production of complex structures became cheaper and therefore rather possible in the recent past. A promising example of such complex structure is a so-called pantographic structure, which can be described as a metamaterial consisting of repeated substructure. In this substructure, two planes, which consist of two arrays of beams being orthogonally aligned to each other, are interconnected by cylinders/pivots. Different inner geometries were taken into account and additively manufactured by means of fused deposition modeling technique using polyethylene terephthalate glycol (PETG) as filament material. To further understand the effect of different manufacturing parameters on the mechanical deformation behavior, three types of specimens have been investigated by means of displacement-controlled extension tests. Different slicing approaches were implemented to eliminate process-related problems. Small and large deformations are investigated separately. Furthermore, 2D digital image correlation was used to calculate strains on the outer surface of the metamaterial. Two finite-element simulations based on linear elastic isotropic model and linear elastic transverse isotropic model have been carried out for small deformations. Standardized extension tests have been performed on 3D-printed PETG according to ISO 527-2. Results obtained from finite-element method have been validated by experimental results of small deformations. These results are in good agreement with linear elastic transverse isotropic model (up to about [Formula: see text] of axial elongation), though the response of large deformations indicates a nonlinear inelastic material behavior. Nevertheless, all samples are able to withstand outer loading conditions after the first rupture, resulting in resilience against ultimate failure.