• Advanced Composite Materials
• /
• v.17 no.4
• /
• pp.373-407
• /
• 2008

This paper will examine the possibilities of the virtual tests of composite structures by simulating mechanical behaviors by using supercomputing technologies, which have now become easily available and powerful but relatively inexpensive. We will describe mainly the applications of large-scale finite element analysis using the direct numerical simulation (DNS), which describes composite material properties considering individual constituent properties. DNS approach is based on the full microscopic concepts, which can provide detailed information about the local interaction between the constituents and micro-failure mechanisms by separate modeling of each constituent. Various composite materials such as metal matrix composites (MMCs), active fiber composites (AFCs), boron/epoxy cross-ply laminates and 3-D orthogonal woven composites are selected as verification examples of DNS. The effective elastic moduli and impact structural characteristics of the composites are determined using the DNS models. These DNS models can also give the global and local information about deformations and influences of high local in-plane and interlaminar stresses induced by transverse impact loading at a microscopic level inside the materials. Furthermore, the multi-scale models based on DNS concepts considering microscopic and macroscopic structures simultaneously are also developed and a numerical low-velocity impact simulation is performed using these multi-scale DNS models. Through these various applications of DNS models, it can be shown that the DNS approach can provide insights of various structural behaviors of composite structures.

• Steel and Composite Structures
• /
• v.12 no.1
• /
• pp.53-72
• /
• 2012

In this study, the physically-based failure models for matrix and fibers in compression and tension loading are introduced. For the 3D stress based fiber kinking model a modification is proposed for calculation of the fiber misalignment angle. All of these models are implemented into the finite element code by using the advantage of damage variable and the numerical results are discussed. To investigate the matrix failure model, purely in-plane transverse compression experiments are carried out on the specimens made by Glass/Epoxy to obtain the fracture surface angle and then a comparison is made with the calculated numerical results. Furthermore, shear failure of $({\pm}45)_s$ model is investigated and the obtained numerical results are discussed and compared with available experimental results. Some experiments are also carried out on the woven laminated composites to investigate the fracture pattern in the matrix failure mode and shown that the presented matrix failure model can be used for the woven composites. Finally, the obtained numerical results for stress based fiber kinking model and improved ones (strain based model) are discussed and compared with each other and with the available results. The results show that these models can predict the kink band angle approximately.

• Transactions of Materials Processing
• /
• v.25 no.6
• /
• pp.402-408
• /
• 2016

A manufacturing technology of carbon fiber composites with thermoplastic polymer pellets and continuous woven fiber was investigated using a compression molding process. To secure the impregnation of resin into the porosity of fabric the composite specimens were prepared with general injection-molding grade polypropylene pellets and low viscosity polycarbonate pellets. Tensile tests of polypropylene and polycarbonate composites were performed. Polycarbonate composites showed higher fracture strength than that of polypropylene composites because of the difference of matrix properties. However, the increase rate of strength was lower than that of polypropylene composites due to the difference of coherence between matrix and reinforcement. To investigate the effect of carbon fiber volume fraction on the fracture strength variation polypropylene composites with different volume fraction were compression molded and tensile tests were performed together. It was shown that the fracture strength of the polypropylene composites increased by 3.2, 5.4 and 6.9 times with the increase of carbon fabric volume fraction of 0.256, 0.367, and 0.480, respectively.

• Composites Research
• /
• v.32 no.5
• /
• pp.296-300
• /
• 2019

Two dimensional transition metal carbides and/or nitrides, known as MXenes, are a promising electrode material in energy storage due to their excellent electrical conductivity, outstanding electrochemical performance, and abundant functional groups on the surface. Use of $Ti_3C_2$ as electrode material has significantly enhanced electrochemical performance by providing more chemically active interfaces, short ion-diffusion lengths, and improved charge transport kinetics. Here, we reports the efficient method to synthesize $Ti_3C_2$ from MAX phase, and opens new avenues for developing MXene based electrode materials for Lithium-Ion batteries.

• Advances in aircraft and spacecraft science
• /
• v.6 no.2
• /
• pp.169-187
• /
• 2019

This work presents a practical detailed finite element (FE) approach for the three-dimensional (3D) free-vibration analysis of actual aircraft and spacecraft-type lightweight and thin honeycomb sandwich panels. It consists of calling successively in $MATLAB^{(R)}$, via a developed user-friendly GUI, a detailed 3D meshing tool, a macrocommands language translator and a commercial FE solver($ABAQUS^{(R)}$ or $ANSYS^{(R)}$). In contrary to the common practice of meshing finely the faces and core cells, the proposed meshing tool represents each wall of the actual hexagonal core cells as a single two-dimensional (2D) 4 nodes quadrangularshell element or two 3 nodes triangular ones, while the faces meshes are obtained simply using the nodes at the core-faces interfaces. Moreover, as the same 2D FE interpolation type is used for meshing the core and faces, this leads to an automatic handling of their required FE compatibility relations. This proposed approach is applied to a sample made of very thin glass fiber reinforced polymer woven composite faces and a thin aluminum alloy hexagonal honeycomb core. The unknown or incomplete geometric and materials properties are first collected through direct measurements, reverse engineering techniques and experimental-FE modal analysis-based inverse identification. Then, the free-vibrations of the actual honeycomb sandwich panel are analyzed experimentally under different boundary conditions and numerically using different mesh basic cell shapes. It is found that this approach is accurate for the first few modes used for pre-design purpose.

• Earthquakes and Structures
• /
• v.16 no.3
• /
• pp.369-373
• /
• 2019

Construction industry is one of the largest markets for composite materials. Composite materials are mostly utilized as surface coatings or concrete reinforcements, and they can hardly be found as a load bearing member in buildings. The three-dimensional composite structures with considerable bending, compressive and shear strengths are capable to be used as construction load bearing members. However, these composites cannot compete with other materials due to higher manufacturing costs. If the cost issue is resolved or their excellent performance is taken into consideration to overcome disadvantages related to economic-competitive challenges, these 3D composites can significantly reduce the construction time and result in lighter and safer buildings. Sandwich composite panels reinforced with 3D woven glass fabrics are amongst composites with highest bending strength. The current study investigates the possibility of utilizing these composite materials to construct ceilings and their application as slabs. One-to-one scale experimental loading of these composite panels shows a remarkable bending strength. Simulation results using ABAQUS software, also indicate that theoretical predictions of bending behavior of these panels are in good agreement with the observed experimental results.

• Composites Research
• /
• v.29 no.6
• /
• pp.342-346
• /
• 2016

Carbon fiber reinforced plastic (CFRP), one of lightweight materials, is the fiber structure using carbon fiber. It is the composite material that has the characteristics of carbon and plastic. As for the fiber structure, it has the great strength due to fiber direction. CFRP for woven type is used mostly as such a CFRP with lightweight. Woven type is more stable when compared with unidirectional type. On the other hand, woven type is highly priced. Therefore, this study aims to analyze the fiber structure of unidirectional CFRP. In this study, as the stacking angle [0/X/-X/0], X is the variable. This is unidirectional CFRP in which the angle phase of X has been reversed and stacked. By using such a unidirectional CFRP, the analysis model which had a crack at the center as the form of panel with the thickness of 2 mm was used. On analysis, the load is applied on the upper and lower parts being connected with a pin. The damage in the area near center crack was investigated. As for the analysis model, 3D surface model was designed by using CATIA. For CFRP stacking, the stacking direction was determined by using ACP in ANSYS program and the analysis model with two stacks was made. Afterwards, the structural analysis was carried out.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.6 no.1
• /
• pp.73-87
• /
• 1996

The mechanical properties of 2D ceramic composites fabricated bythe newly developed powder infiltration and subsequent multiple impregnation process were characterised by both 3-point flexure and tensile tests. These tests were performed with strain gauge and acoustic emission instrument. The woven fabric composites used for the test have the basic combinations of $Al_{2}$$O_{3}$ fabric/$Al_{2}$$O_{3}$ and SiC fabric (Tyranno)/SiC. Uniaxially aligned SiC fibre(Textron SCS-6)/SiC composites were also tested for comparison, The ultimate flexural strength and first-matrix cracking stress of SiC fabric/SiC composite with 73% of theoretical density were about 300 MPa and 77 MPa respectively. However, the ultimate tensile strengths of composite were generally one third of flexural strengths, and first-matrix cracking stress in a tension test was also much lower than the value obtained from flexure test. The lower mechanical properties measured by tension test were analysed quantitatively bythe differences in stressed volume using Weibull statistics. This showed that the ultimate strength and the firs-tmatrix cracking stress of woven laminate composites were mainly determined bythe gauge length of fibres and the stressed volume of matrix respectively. Incorporation of SiC whiskers into the matrix increased first-matrix cracking stress by increasing the matrix failure strain of composites.

• Journal of Fashion Business
• /
• v.19 no.4
• /
• pp.153-167
• /
• 2015

This paper proposes knit slacks patterns by lower body shape of middle-aged women. In addition, this paper aims to propose a design method for a prototype of nice knit slacks using the properties of knitwear. To select basic woven slack patterns which would be used in designing prototype of knit slacks for middle-aged women, two industrial slack patterns and two educational slack patterns were collected, and lab coats were prefabricated using muslin. Then, a shape test was performed by an evaluation board which consisted of eight experts who majored in Clothing Construction. Using blended yarn (1/17's) with 64% wool, 23% rayon and 13% nylon, 12G knit slacks in plain stitch were made. In terms of waist circumference of knit slacks, the front and the back were set to W/4+1+2(D) and W/4-1+2(D), respectively, with 1cm of difference using waist circumference (Omphalion) to cover the abdominal circumference. To make the front-back width of the side line even, the front waist circumference was increased by 1cm. The ease of hip circumference was set to 4cm in total with H/4+1+0.8 in front and H/4+1-0.8 in the back (0.8cm in difference). Crotch length was set by adding 3cm (width of waist belt) after deducting crotch height from waist height (Omphalion). The center front angle was shifted by 1cm while the center back angle was shifted from the center front to the side line by 5cm.

• Textile Coloration and Finishing
• /
• v.20 no.3
• /
• pp.1-7
• /
• 2008

Three kinds of 135D/108F ITY were produced from raw yam 85D/72F + SDY 50D/36F with. interlacing pressure $1.5kg/cm^2$, $2.5kg/cm^2$, $3.5kg/cm^2$ respectively. 72 kinds of sized yams were manufactured from three ITYs by altering sizing speed, sizing temperature and sizing tension. The mechanical characteristics of 72 kinds of plain fabrics which were woven using the sized yam as a warp were analyzed after scouring. The initial modulus of scoured fabric responded sensitively to the sizing speed in high tension. The WT of scoured fabric recorded the. highest1n the conditions of sizing tension 30g, and air pressure $2.5kg/cm^2$ in interlacing treatment. When sizing temperature was high, the WT value appeared low, but when sizing speed was high, the WT value was much affected by air pressure in interlacing raw yam. The MIU value of fabric according to sizing tension variations increased up to sizing tension 40g, but decreased above it. The bulk density decreased up to sizing tension 30-40g, but increased above it. In addition, the bulk density decreased as sizing temperature increased.