Effects of micromechanical factors in the strain invariant failure theory for composites

Master'sMASTER OF ENGINEERIN

Post-consolidation process for modifying microscale and mesoscale parameters of 3D printed composite materials

Advancements in additive manufacturing technology (3D printing) have enabled us to fabricate reasonably good parts using continuous fiber-reinforced matrix composites. Unfortunately, most of these 3D-printed composite parts inherently possess a large number of voids originating from the trapped air within and between molten composite beads during the deposition stage. Removing the voids has thus become a key challenge in attempts to apply 3D printed composite parts for fabricating stiff/strong load-bearing structures. Here, we employed a classical process, viz. compression molding, to post-consolidate 3D-printed continuous carbon fiber-reinforced polyamide (CFPA), and to investigate the implications in terms of microscale parameters (void content) and mesoscale parameters (mechanical properties, plasticity, damage) using matrix-dominated lay-up of [±45]2s. We found that the proposed post-consolidation process could reduce the void of 3D-printed CFPA from 12.2% to 1.8%, enhancing the shear modulus and shear strength by 135% and 116%, respectively. The mesoscale analysis shows that, albeit with less ductility, the post-consolidated CFPA laminate was more resistant to damage than the 3D-printed CFPA. Classical compression molding is thus a promising technique for improving the physical and mechanical performances of 3D-printed composites by reducing inherent void built-ups

Analisis Strategi Produk Smart Panin Pada PT. Panin Bank, Tbk

Companies have a tendency to compete with other companies engaged in similar business. Company in order to maintain its viability in order to survive in the competitive climate should have a strategy in creating products of excellence to attract consumers to switch to its products. In conducting its business, the Panin Bank's product namely SMART Integration compete with others who have similar products. To face the competition so that product development strategy is needed to achieve corporate goals. The purpose of this study was to determine the company's strategic alternatives in developing SMART products Panin using SWOT analysis. This research is a descriptive study with qualitative data support. Data collection techniques gained through in-depth interviews as well as real data in the field of internal and external. Based on the results of the SWOT analysis, the resulting nine alternative strategy, namely (1) Carry out a good promotional activities so that potential customers know SMART Panin; (2) Maintain and improve the position of the national rankings in order to improve the bank's reputation in the eyes of the public; (3) Making changes more flexible system in particular in the field of revenue assurance; (4) Increase the number of KCU order to facilitate prospective customers when credit agreement; (5) Conduct an attractive promotions that keep customers willing to put their money in the bank; (6) provide an interesting variety of products as well as competitive rates; (7) Taking more policy refers to the ease of customers; (8) Improving and promoting attractive; (9) Continuously innovate as a form of readiness to compete with other banks

静的および疲労荷重下での炭素繊維／エポキシ縫合複合材の力学特性と損傷メカニズム

Objective of this thesis is to understand the effect of stitch parameters (stitch density, stitch thread thickness, stitch pattern, stitch orientation) on the in-plane mechanical properties and damage mechanisms of Vectran-stitched and Kevlar-stitched carbon/epoxy composites under static and fatigue loads. Experimental test series comprising static tension, static compression, open hole tension, open hole compression, tension-tension and compression-compression fatigue tests are performed. Characterization of architectural changes induced by stitching process, e.g. fiber breakage, fiber waviness, resin-rich region, stitch debonding, and their correlation with mechanical performance and damage mechanisms is discussed in details. Two analytical works are also described in this thesis: first, a multi-scale modeling scheme to predict 3-D thermo-elastic constants of stitched composites by employing asymptotic expansion homogenization method; second, application of Average Stress Criterion to predict open hole tension strength of stitched composites. Investigation of Vectran-stitched composites shows that moderately stitched composites (stitched 6x6; moderate stitch density) under static tension experience a slight strength reduction, while densely stitched composites (stitched 3x3; high stitch density) exhibit a modest improvement of strength in comparison with unstitched composites. Stitching with either stitch density is found to promote a vast number of cracks, but densely stitched composites are sufficiently effective in impeding the growth of delamination, which translates into higher tensile strength. Accordingly, under fatigue loads, densely stitched composites exhibit better fatigue life due to similar mechanism: delamination impediment provided by the stitches. Tensile modulus of stitched composites is slightly reduced mainly due to fiber waviness. Compression tests on Vectran-stitched composites show that regardless stitch density or thread thickness stitched composites generally exhibit lower compressive strength than unstitched composites. Stitching induces a formation of resin-rich region, which triggers early cracking, fiber splitting and fiber kinking at relatively lower compression load. Analytical work dealing with the predictions of 3-D thermo-elastic constants of Vectran-stitched composites shows that homogenization results are in a good agreement with the experiments. Investigation of Kevlar-stitched composites shows that stitched composites with hole are sensitive to stitch orientation, in which transverse stitching (perpendicular to loading direction) significantly reduces tensile strength due to stitch debonding and ensuing interaction amongst debondings. On the other hand, stitched composites with holes are independent of stitch orientation because the failure is greatly controlled by the stress concentration at the hole rims that surpasses the criticality of stitch debonding. Thus, normal stress distribution in Kevlar-stitched composites with holes can be estimated by Lekhnitskii theory, and open hole tensile strength can be estimated by Average Stress Criterion. Investigation of Kevlar-stitched composites under fatigue loads reveals that stitch pattern of round stitching (stitches encircling the holes) reduces .fatigue life due to damage acceleration around the hole rim, whilst parallel stitching does not pose any significant effect on fatigue life. Finally, recommendation on how to improve the mechanical performance of stitched composites is given. This thesis endorses that stitching is an effective through-thickness reinforcement method for composites in the next generation aircraft.首都大学東京, 2013-03-25, 博士 (工学), 甲第372号首都大学東

Peningkatan Keamanan Perjalanan Kereta Api Dengan Penggunaan Sistem Axle Counter Dan Media Transmisi Fiber Optic Untuk Hubungan Blok Di Persinyalan VPI (Studi Kasus Hubungan Blok Stasiun Surodadi - Pemalang)

Penelitian ini disusun untuk membuat suatu alternatif penyelesaian gangguan pada  peralatan  blok Stasiun Surodadi dan Pemalang dalam rangka meningkatkan keamanan perjalanan kereta api  di Stasiun Surodadi-Pemalang. Penelitian ini menggunakan landasan teori  dan  peraturan  yang mendukung penyelesaian masalah dengan pengkajian melalui aspek teknis, aspek operasional dan aspek keselamatan. Hasil  penelitian  ini  menunjukkan  bahwa  sistem  axle  counter  relatif  lebih hemat, aman dan efisien dibandingkan track circuit. Sistem transmisi fiber opticlebih efisien dan menguntungkan dibanding sistem transmisi kabel. Sebagian keterlambatan  juga  diakibatkan  gangguan peralatan  persinyalan  dan  salah  satunya  adalah  gangguan  hubungan  blok.  Dalam keadaan hubungan blok terganggu, pemberangkatan kereta dengan sinyal darurat memungkinkan terhadinya kecelakaan yang diakibatkan oleh faktor kelelahan dan kondisi psikologis PPKA. Guna mengurangi keterlambatan  kereta  api,  mengurangi  resiko  kemungkinan  terjadinya   kecelakaan akibat pemberian bentuk darurat 1 (D.1) secara bersamaan oleh  PPKA  kedua  stasiun  yang terganggu hubungan bloknya dan meningkatkan keamanan perjalanan kereta api, sebaiknya track circuit petak jalan diganti dengan dua buah axle counter  yang  dipasang  di sinyal  masuk  stasiun untuk mendeteksi  keberadaan  bakal  pelanting  di  petak  jalan,  penelitian  ini  juga merekomendasikan agar penggunaan kabel fisik diganti menjadi kabel fiber optic

Finite element procedure to simulate sandwich structure with an auxetic core under impact loading using ABAQUS/Explicit

<p>A sandwich structure with an auxetic core is promising in improving the performance of a sandwich structure by implying an auxetic core as its core to combine the advantages of the two structures, e.g., sandwich structure's superior ability in flexural and shear resistance, auxetic structure in localizing damage, and densification phenomena. This paper discusses a finite element modeling procedure to simulate a sandwich structure with a heterogeneous re-entrant auxetic core. The material of the face is a unidirectional carbon fiber reinforced polymer (UD CFRP) and the core is polylactic acid (PLA). The model is subjected to a low-velocity impact loading and is run through the ABAQUS/Explicit software. We found that the model we developed here could simulate up to the elastic region and identify which element had failed. However, it could not fully resemble and represent the model from reference, where fracture or damage does not occur. This model can be further improved in its material modeling strategy, especially in the fracture modeling of the composite face with compatible material properties in all required sectors, especially damaged sections, which are strictly necessary.</p&gt

Modeling of single-lap joints with auxetic adhesive utilizing homogeneous and heterogeneous bondline microstructures

Producing lightweight structures can be effectively achieved using adhesive bonding that incorporates a high-performance adhesive, eliminating the mechanical joints (rivet, bolts). Here, the proof-of-concept of tailoring the high-performance adhesive using microstructures exhibiting a negative Poisson's ratio (auxetic) is investigated using two single lap joint (SLJ) models developed in ABAQUS/Standard. The SLJ models consist of two rigid adherends that are bonded using either homogeneous or heterogeneous adhesive that produces auxetic response. In homogeneous adhesive, a negative value of Poisson's ratio is defined in the adhesive part of the models. In heterogeneous adhesive, the negative Poisson's ratio is obtained by explicitly building orthogonally-arranged elliptical voids in the adhesive part of the models. In addition, the adherend-adhesive interface is represented by cohesive elements with bi-linear traction-separation rule. The effects of using two different adhesive models and thickness on peel and shear stresses, as well as failure mechanism and joint strength, are evaluated. We found that the effect of auxetic adhesive on SLJ response is more profound in the model using heterogeneous adhesive rather than the homogeneous one, where the joint strength enhancement could achieve 45 % in reference to the baseline model. The heterogeneous adhesive embedded between adherends is able to activate ligaments, the mechanism that could not be obtained using merely homogeneous adhesive. Our proposed modeling strategy can be a starting point to further the modeling approach of bonded joints utilizing auxetic adhesive