Papers by Author: Hirotsugu Inoue

Abstract: This present study has been re-established to investigate failure mode and resistance characteristics of the PC/ABS blends and their ABS constituents under impact for a range of rubber contents. This present study has still been experimentally performed under an instrumented-drop weight impact test (DWIT) at a room temperature. It has been finally revealed that with a particular size of rubber particle, content of rubber significantly influenced impact failure modes and impact resistances of the PC/ABS blends and their ABS constituents as well. The test results showed that impact strength of the blends was improved about 23.22% and 155.33% due to increase in content of rubber up to 15 wt% and 20 wt%, respectively. There was also found that an increase in impact toughness of the blends for 57.48% and 239.23% was due to increase in content of rubber up to 15 wt% and 20 wt%, respectively. Whilst, impact strength of the ABS was improved about 392.98% and 190.12% due to increase in content of rubber up to 15 wt% and 20 wt%, respectively. An increase in impact toughness of the ABS for 308.20% and 172.56% was due to increase in content of rubber up to 15 wt% and 20 wt%, respectively.

Abstract: This study presents an experimental study on failure modes and resistances of polycarbonate (PC)/Acrylonitrile Butadiene Styrene (ABS) blends and their ABS constituents under a drop weight impact test (DWIT). Failure modes and impact resistances such as impact strength and impact toughness of such blends are generally influenced by molecular weight of the PC, rubber content and size of rubber particle in ABS system. A preliminary study on ABS materials using a DWIT showed that size of rubber particle not only determined their failure modes but also influencing their resistance characteristics. However, in a previous study performed using the similar DWIT on PC/ABS blends with a 10 wt% rubber content, it was revealed that size of rubber particle did not significantly influence their resistances. Their failure modes were even macroscopically very difficult to be distinguished. This study, hence, is aimed to further explore role of the size of rubber particle on failure mode and impact resistance characteristics of the PC/ABS blends and their ABS constituents with a higher rubber content. The impact test results have revealed that with a 20 wt% rubber content, size of rubber particle only influenced the resistances of the PC/ABS blends. It did not significantly contribute to affect failure mode of the PC/ABS blends. Whilst, it significantly influenced failure modes and resistances of the ABS. The DWIT results also re-confirmed that blending a brittle ABS into PC led to produce a tougher PC/ABS blend.

Abstract: Experimental works using a drop weight impact test method have been performed on a circular sheet specimen to evaluate and to characterize the impact resistance of the sheet-type plastic components designed for automotive wheel covers. Evaluation has been conducted for a set of engineering plastics: polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS) and their blend (PC/ABS). The testing results showed that the PC/ABS blend specimens failed in brittle manner under higher impact speeds with very few of whitening zones. Secondary cracks captured perpendicular to fracture surface were also found in the mid-plane of the scattered PC/ABS blend specimens. Investigation is then focused on this blend and the testing results describe that impact resistance of the specimen made of this alternative material is determined by ABS not by PC. Combination of structures between PC and ABS through the thickness in the core due to their immiscibility was observed by scanning electron microscope (SEM) on the etched PC/ABS specimen. This latter result well correlates the results obtained from the testing. It therefore reveals that immiscibility between PC and ABS in the blend plays an important role in determining the impact resistance of the components. This paper also presents simulative results of the test obtained from a FEA work by introducing a 3D- layered finite element (FE) model of the PC/ABS specimen to take into account effect of a layer in the core on the behavior of the blend.

Abstract: Adhesives are widely used in our life and industrial world. However, it is difficult to characterize their mechanical properties because those strongly depend on environmental and mechanical conditions such as temperature, humidity or strain rate. In this paper, we focus on the strain rate dependence of the interfacial strength and investigate the interfacial strength by peel tests under several peel rates. The results show that, in lower rate region (under 1.0 mm/s), the interfacial strength is constant and, in transition region (1.0 to 10 mm/s) the interface strength increased with the peel rate. In middle rate region (10 to 103 mm/s), the interfacial strength is constant again. Over 103 mm/s region, the interfacial strength drops and became lower than those in middle rate cases. From the observation of peeling front by a high speed video camera, the deformation behavior of adhesives changes with the peel rate.􀀁Finite element analysis by using cohesive zone model is also conducted, and influence of the rate dependency of adhesive and base material is discussed.

Abstract: A method to predict impact load caused by drop impact of thin cone-shaped structures is investigated. The Hertzian contact theory and the spherical shell theory are applied for modeling the contact stiffness of the impact tip of the cone. Experiments and finite element simulations are performed for several cones to evaluate the accuracy of impact load prediction. It is shown that appropriate choice of contact stiffness model depending on the curvature and thickness of impact tip of the cone is necessary in order to predict the impact load accurately.

Abstract: The aim of this paper is to evaluate the cyclic interfacial strength between thin film and its substrate by cyclic nano-indentation tests. The specimen used in this study is PET substrate/ITO coatings layered specimen. From the indentation load and displacement curve, we proposed an evaluation method for the interfacial strength. The results are good agreement with the interfacial strength evaluated by peel test. After cyclic indentations, the surface profile was observed by atomic force microscope. The number of elongates increased with indentation cycles when the indentation load is low, whereas elongates number is almost constant under high load cases. These phenomena can be explained by simple models. In this study, two types of fracture modes are proposed. They are “subsidiary fracture mode” and “buckling mode”.

Abstract: The stochastic nature of aluminum foam structure, having a random distribution of voids, makes it difficult to model its compressive deformation behavior accurately. In this paper, a 2-dimensional simplified modeling approach is introduced to analyze the compressive deformation behavior that occurs in Alporas aluminum foam (Al foam). This has been achieved using image analysis on real undeformed aluminum foam images obtained by VHX-100 digital microscope. Finite element mesh for the cross sectional model is generated with Object Oriented Finite element (OOF) method combined with ABAQUS structural analysis. It is expected that OOF modeling enable prediction of the origin of failure in terms of localized deformation with respect to the microstructural details. Furthermore, strain concentration sites leading to the evolution of the deformation band can be visualized. Thus, this investigation addresses the local inhomogeneity in the Al foam structure. This study implies that the OOF modeling approach combined with experimental observations can provide better insight into the understanding of aluminum foam compressive deformation behavior.

Abstract: Adhesives are widely used in industrial world. However, it is difficult to characterize their mechanical properties because those strongly depend on environmental and mechanical conditions such as temperature, humidity or strain rate. In this paper, we focus on the strain rate dependence of the interfacial strength and investigate the interfacial strength by peel tests under several peel rates. The results show that, in low rate case (under 10-2 mm/s), the interfacial strength was constant and, in middle rate case (10-2 to 103 mm/s), the interfacial strength increased with the peel rate. Over 103 mm/s case, the interfacial strength became lower than those in middle rate cases. From the observation of peeling front by a high speed video camera, the deformation behavior of adhesives changed with the peel rate.

Abstract: An instrumented-drop weight impact test carried out at room temperature under a range of loading rates was applied to study the deformation and failure behaviors of PC/ABS (50/50) blends. Actually, these blends have different type of ABS, one grade of the blends is the blend containing small-sized particles of rubber and another grade is the blend containing larger-sized particles of rubber in the ABS systems. Testing results showed that both of the blends generally exhibited similar behaviors but they were totally different under 3 m/sec. A weld line-like formation captured on the fracture surface was found in each of the blends. Preliminary study using scanning electron microscope (SEM) indicated that crack also propagated along the weld line. Fracture of the blends might be initially induced due to fracture of the weld lines. Hence, it has been suspected as a factor affecting behavior of the blends. Since existence of the weld line-like formation has not been found in fractured ABS materials, it is necessary to point out the complex relationship among of the ABS composition, the existence of the weld line and the weld line quality in the blends. A finite element (FE) simulation of the testing was carried in order to determine whether the weld line strength is significant enough affects the behaviors. Although the model was generated using estimated failure criterion for the weld line, the simulation results showed that weld line strength might influence the blends behavior.

Abstract: Based on previous available constitutive models, a phenomenological constitutive model has been constructed and is proposed to describe the strain, strain rate and temperature dependentdeformation behavior of PC/ABS blends. In this paper, four quasi-static uniaxial tension tests of a specimen tested at different strain rates and temperatures were used to identify the constitutive model constants. By using the proposed constitutive model, predicting the stress-strain behavior of the PC/ABS blend tested at certain strain rate and different temperatures compares well to the behavior exhibited from the tests. From comparison between the DSGZ and the proposed models, proposed model shows a better prediction. Evaluation of the proposed constitutive model was also presented and it has revealed that the proposed model might have a potential to be used for predicting a wide range of temperatures and high strain rates behavior of PC/ABS blends.