STUDY ON THE STRENGTH OF LAP-JOINT OF GLASS/POLYESTER COMPOSITE WITH DIFFERENT SURFACE PROPERTIES

Pham Thanh Nhut,Tae Hyoung Kim,Young Jin Yum 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11

The lap-joint composite samples were fabricated by hand lay-up and vacuum method at room temperature whose main components are unsaturated polyester, fiberglass woven and mat. The adhesive used in joints is also unsaturated polyester resin. Joining process of the specimens was performed on six types of surface with two different methods: terminal-joint and secondary-joint but the same geometry properties. Experiment method was used to determine the mechanical properties of adhesive, adherends, terminal-joint and secondary-joint specimens. The tensile test results and geometry parameters of specimens were combined with bonding theory to calculate the maximum and average shear stresses. Six joints were compared and evaluated together by the results of maximum and average shear stresses. From the results, it was observed that grind/acetone case had the highest strength in three types of terminal-joint and grinding case had near the same value. For secondary-joints, mat-mat and mat-woven case had the highest strength with the same value. While no treatment and woven-woven bonding had very low strength. For failure tendency, it occurred strongly at two ends and then moved to the middle area of overlap length in x-z plane but only appeared at an edge and then spread to opposite edge in x-y plane.

Study on Improved Methods for Interfacial Properties of Gelcoat-Composites

Pham Thanh Nhut,Tae Hyoung Kim,Young Jin Yum 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12

Gelcoat resin is applied to improve the surface properties of composite materials. Combinations of gelcoat and glass/epoxy or carbon/epoxy will make a perfect composite structure. However, mechanical properties of these bonds need to study before application. Two pairs of material (glass/epoxy-gelcoat, carbon /epoxy-gelcoat) were studied to improve the interfacial properties by experiment with four treatment methods on the surfaces of outer and inner adherends. Three different tests (single-leg bending, peel and single lap-joint) were carried out for above works. Experiment results were combined with equations to obtain the strength or energy. From the results, it was observed that the strength or energy of of GEG and CEG material were almost the same. After using the treatment methods of surfaces, the energy and strength of four methods were higher than the values of initial surfaces. The P-method has the lowest and GAP-method has the highest strength or energy. G-method and GA-method were better than P-method but negligible.

Evaluation of cavitation erosion of a propeller blade surface made of composite materials

Nhut Pham-Thanh,Hoang Van Tho,염영진 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.4

Cavitation erosion strongly impacts the efficiency and strength of marine propellers. This is more important for propellers made fromdifferent types of composite materials. Thus, an investigation of cavitation erosion on the blade surface of composite ship propellers isnecessary. A small three-blade propeller was made from fiberglass combined with epoxy, polyester and gelcoat resin. This propeller wastested in a circulating water channel and revolution speed and depth were determined by conditions of cavitation number. Cavitation erosionwas observed and evaluated by images, weight loss and cavitation area. The results indicated that the cavitation erosion occurred atregions 0.4 R (Radius) and 0.7 R from the center, and cavitation also occurred randomly on pressure or suction surfaces and leading ortrailing edges. Most damaged regions propagated along the circumferential direction of the propeller. Among the blade materials, the Ge-GF blade had the best property. This material had the smallest cavitation area and the most stable cavitation area rate. The Po-GF blade hadthe worst property with strong progression of the cavitation area, and the Ep-GF blade was of medium quality with a small reduction of thedamage area rate. Besides, the depth of the damaged area of the Ge-GF blade was also lower than that of the Ep-GF and Po-GF blade.

THE EFECT OF SURFACE PROPERTIES ON THE JOINT STRENGTH OF GLASS/POLYESTER COMPOSITE

Pham Thanh Nhut,Young Jin Yum 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.5-2

적층복합재료구조물의 변형에 미치는 제작조건과 작동조건의 영향에 대한 실험적 고찰

팜탄눗 ( Pham Thanh Nhut ),염영진 ( Young Jin Yum ) 한국복합재료학회 2013 Composites research Vol.26 No.4

섬유강화플라스틱(Fiber-reinforced plastic, FRP)은 복합재료 보트를 만드는 데 주 구조물로 사용되고 그것들 대부분은 몰드에서 만들어진다. 이러한 제품들은 몰드에서 분리될 때나 높은 온도의 환경에서 변형이 생긴다. 그러므로 다양한 제작 및 작동 조건에서 적층복합재료 구조물의 변형에 대한 실험적 조사 및 평가는 필수적이다. 불포화 폴리에스테르수지와 유리섬유를 이용하여 L-shape과 Curve-shape 시편을 제작하였다. 경화제 비율과 제작온도, 네 가지 작동온도가 입력인자(독립변수)로 사용되었고 출력인자는 시편에서 측정되는 변형이다. 결과로부터 경화제 비율이 높을수록 또한 제작온도가 높을수록 변형이 작게 생김을 알 수 있었다. 작동온도가 상승할 때 초기 변형 값에 따라 큰 변화를 보였다. 또한 변형 값이나 입력인자들은 회귀 방정식으로부터 예측할 수 있었다. Fiber-reinforced plastic (FRP) is applied to fabricate the main structures of composite boats. Most of them are made from molds. These products deform after releasing from the mold and they also deform in high temperature environment. Therefore, experimental investigation and evaluation of deformation of laminated composite structures under various manufacturing and working conditions are necessary. The specimens of L-shape and curveshape were made from unsaturated polyester resin and fiberglass material. Input factors (independent variables) are percentage of hardener and manufacturing temperature and four levels of working temperature and output factor is the deformation which is measured on these specimens. From the results, it was observed that the higher the hardener rate and temperature, the lower the deformation. When the working temperature increased, the specimens showed great variations for the initial deformation values. Besides, the values of deformation or input factors could be predicted by regression equations.

소형 복합재료 프로펠러를 위한 복합재료 몰드 평가

팜탄누트(Pham Thanh Nhut),염영진(Young Jin Yum) 대한기계학회 2013 大韓機械學會論文集A Vol.37 No.2

소형 복합재료 프로펠러를 제작하기 위한 기존의 알루미늄 몰드를 복합재료 몰드로 대체하기 위한 타당성 연구를 수행하였다. 소형 알루미늄 프로펠러의 세 날개는 복합재료 몰드를 만들기 위해 플러그로서 사용되었다. GRPG 복합재료 몰드와 프로펠러는 실내온도에서 압축과 진공법을 이용하여 불포화된 폴리에스테르 수지, Epovia 겔코트, 우븐과 매트 유리 섬유 등으로 만들어졌다. 표면의 경도와 거칠기, 압축과 흡입 몰드에 의한 강도와 변형은 실험에 의해 결정되었다. 결과는 ISO 484/2 규격과 몇몇의 알루미늄 합금과 비교되었다. 결과로부터 몰드의 변형은 날개 두께에 관한 공차를 만족하는 것을 알 수 있었다. GRPG 복합재료 몰드의 몇 가지 특징은 알루미늄 합금 몰드보다 좋았으며(표면의 매끈함, 중량, 작동 능력과 비용), 다른 몇 가지 특징들은 비슷하였다(분리 능력과 라이프 사이클). 결과적으로 복합재료 몰드는 소형 복합재료 선박 프로펠러를 만들기에 적합한 것을 알 수 있었다. The feasibility of substituting a composite mold for an aluminum mold in the fabrication of a small ship propeller was investigated. A small three-blade aluminum propeller was used as a plug for manufacturing the composite mold. A GRPG composite mold and propeller were made from an unsaturated polyester resin, Epovia gelcoat, and woven and mat glass fibers using the compression and vacuum method at room temperature. The hardness and surface roughness and the strength and deformation of the compression and suction molds were experimentally determined. The results were compared with the ISO 484/2 standard and some aluminum alloy materials. The results showed that the deformation of the mold satisfied the tolerance of the thickness of the blade. Some characteristics of the GRPG composite mold were better than those of the aluminum alloy mold (surface smoothness, weight, performance, and cost), and some characteristics were similar (detachment ability and life-cycle). Therefore, the composite mold is considered suitable for the fabrication of a small composite ship propeller.

유리섬유/폴리에스테르 복합재료 패널 접합부의 접착강도에 관한 표면성질의 효과

팜탄눗(Pham Thanh Nhut),염영진(Young Jin Yum) 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.12

복합재료 접합부의 접착강도에 대한 접착면 성질의 영향을 알아 보기 위해 불포화폴리에스테르, 우븐과 매트 유리섬유를 사용하여 복합재료 접합시편들을 제작하였다. 접착제, 복합재료 접착물, 말단접합과 이차접합 시편들의 기계적 성질을 실험에 의해 구하고 실험결과를 접합이론에 적용하였다. 6 개의 접합부들에서 발생하는 최대 및 평균 전단 응력은 최대 인장력과 접합 시편의 기하학적 변수들로부터 계산되었다. 실험 결과 접합면을 연마한 후 아세톤으로 처리한 경우가 말단접합의 3 가지 형태 중 가장 큰 강도를 가지고 있음이 관찰되었다. 마찬가지로 매트-매트와 매트-우븐 접합이 거의 같은 값으로 이차 접합의 3 가지 형태 중 가장 큰 강도를 가지고 있었다. 반대로 아무 처리도 하지 않은 접합시편과 우븐-우븐 접합시편은 매우 낮은 강도를 가졌다. 각각의 경우 파손은 접합부 양끝에서 심하게 발생하였고 접합부 가운데로 이동하였다. Adherend samples were made from unsaturated polyester and woven and mat glass fibers by the hand layup and vacuum methods. The mechanical properties of the adhesive, composite adherends, and terminal-joint and secondary-joint specimens were determined experimentally. Combinations of the experiment results and the bonding theory were used in this study. The maximum and average shear stresses were calculated based on the maximum tensile force and geometry parameters of the joint specimens. The results of the maximum and average shear stresses were compared and evaluated for six joints. The results showed that the grinding and grind/acetone joint had the highest strength among three types of terminal-joints. Similarly, the mat-mat and mat-woven joints had the highest strength among three types of secondary-joints with the same value. Conversely, no treatment and woven-woven bonding had very low strength. In each case, failure occurred always at two ends and then moved toward the middle area of the overlap length.

TENSILE, FLEXURAL PROPERTIES OF WOVEN JUTE/GLASS AND JUTE/SILK HYBRID COMPOSITES

P. Noorunnisa Khanam,Chi Hoon Jeon,Pham Thanh Nhut,Young Jin Yum 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10

Unsaturated polyester based woven jute/glass and woven jute/silk fibre hybrid composites were prepared by hand layup method. Mechanical properties like tensile and flexural properties were studied for these hybrid composites. Tensile and flexural properties were also studied for woven jute, woven silk fibre composites and also for matrix. The results of jute/glass and jute/silk composites were compared with the results of jute/silk hybrid composites. From the results, it was observed that jute/glass hybrid composites showed better properties than jute/silk fibre reinforced hybrid composites. It was also observed that jute fibre properties were improved by adding glass and silk fibre in hybrid composites. Mechanical tests were carried out by using ASTM methods.