Papers by Keyword: Collapse Mode

Abstract: –The behaviour of extruded glass fibre reinforced thermoplastic pipe under axial crushing load was investigated experimentally. It was envisaged that the difference between the axial and hoop moduli and strengths as well as the volume fraction would influence the mode of collapses and energy absorption. The moduli could be varied using a new extrusion technology, which controls the fibre orientation pattern, hence, the mechanical properties. The ability to vary the moduli and the fibre volume fraction provide means of controlling the collapse mode in order to optimise specific energy absorption. Axial compression tests were performed on glass filled Polypropylene and Polyethylene composite pipes. The samples were chosen with a variety of fibre volume fraction, V_f = 5% to 20% and average angle of orientation, θ = 50^o to 80^o to evaluate the effect of anisotropy and V_f on the energy absorption capacity and collapse modes. The observations indicate that, the samples containing of higher V_f and θ, collapsed in brittle failure mode (fragmentation), while those with less V_f and θ angle collapsed in non-axis-symmetric (diamond) mode with local fracture. The galss fillet with polypropylene-60^o (GPP-60) displayed the highest specific energy absorption (E_s) compared to the other GPE, MDPE and LDPE pipe samples. However, the glass fillet polyethylene – 75^o (GPE-75) displayed the highest E_s and the glass fillet polyethylene – 65^o (GPE-65) displayed the lowest E_s compared with in the GPE pipes. The specific energy absorption of GPP-70 pipe (24 kJ/kg) and GPE-75 pipe (12 kJ/kg) is almost 50 % and 25% of the amount of specific energy absorption of aluminium tubes (60 kJ/kg), respectively. Moreover, it is close to the specific energy absorption of glass-epoxy 15^o (GE-15) / which is 30 kJ/kg, and much higher than aramid-epoxy-15^o (AE-15)/ which is 9 kJ/kg.

Abstract: CFRP (Carbon Fiber Reinforced Plastics) is an anisotropic material which is the most widely adapted lightweight structural member. CFRP of the advanced composite materials as structure materials for vehicles has a widely application in lightweight structural materials of air planes, ships and automobiles because of high strength and stiffness. The CFRP Square members were made of 8ply unidirectional prepreg sheets stacked at different angles and interface numbers. Based on the collapse characteristics of CFRP member, the collapse characteristics and energy absorption capability were analyzed. The impact collapse tests were carried out for each section member. The purpose is to examine experimentally absorption behavior and strength evaluation depending on changes in the stacking configuration when the CFRP Square member s with different stacking configuration is exposed to separate impact velocity.

Abstract: This study is intended to show possibility of using high strength steel for H-shaped beams with large depth-thickness ratio in the elastic range by conducting loading tests. Test specimens are manufactured with high strength steel of over 700N/mm2 yield stress. Elastic behaviors of such beams under cyclic loading are mainly concerned. In addition, the redundancy and the stability of these beams in plastic range are investigated. It is shown that these beams are useful as seismic design beams although the depth-thickness ratio of H-shaped beams is larger than the limit of current standards in Japan. Also, by referring to a recent study, a new limit value of plate slenderness ratio (depth-thickness ratio of web plate and width-thickness ratio of flange plate) is proposed.

Abstract: In order to investigate the collapse mode of double-layer space trusses, the whole collapse process is simulated by the explicit finite element methods. The calculation results indicate that horizontal earthquake and vertical earthquake waves will lead to two typical collapse modes of the structure. The collapse mode of the structure under horizontal earthquake are mainly strength failure, which is characterized by the failure of members connected to the columns; the collapse mode of the structure under vertical earthquake are mainly dynamic instability, which is characterized by the V shape deformation. The analytical results agree with the experimental results.

Abstract: Currently, the most important objective in designing automobiles is to focus on environment-friendly and safety performance aspects. For the environment-friendly aspect, the issues relate to the shift towards lightweight automobile production, for improving fuel-efficiency and reducing exhaust fumes. However, in contrast, the issues of the safety performance such as crash safety, comfort level and muti-functional programs demand increase of automobile’s weight. Therefore, the design of automobile should be inclined towards the safety aspects, but at the same time, it also should consider reducing the structural weight of an automobile. In this study, for lightweight design of side member, CFRP side member was manufactured from CFRP unidirectional prepreg sheet. The stacking condition related to the energy absorption of composite materials, is being considered as an issue for the structural efficiency. Therefore, the axial collapse tests were performed with change of the stacking condition, such as fiber orientation angle and interlaminar number. The collapse modes and energy absorption characteristics were analyzed according to fiber orientation angle and interlaminar number.

Abstract: Currently, stacking condition related to the energy absorption of composite materials is being considered as an issue for the structural efficiency and safety of automobiles, aerospace vehicles, trains, ships even elevators during collision. In particular, CFRP (carbon fiber reinforced plastics) composite materials have found wide applicability because of their inherent design flexibility and improved material properties. The most important objective in designing automobiles is currently to focus on environment-friendly aspect and safety performance aspect. Therefore, the designing automobile should be more concerned on the aspect of securing safety performance, but at the same time, it also should consider reducing weight of automobile structural member. In this study, CFRP (Carbon Fiber Reinforced Plastics) side members with single-hat-section shaped were manufactured. The axial static collapse tests were performed for the members using universal testing machine, and the collapse mode and energy absorption characteristics were analyzed according to stacking condition such as fiber orientation angle and shape of the section.

Abstract: The purpose of this study was to develop lightweight hat shaped section side members which absorb the most of the energy during the front-end collision of vehicle. The hybrid side member was manufactured by combination of aluminum and CFRP. An aluminum or CFRP (Carbon Fiber Reinforced Plastics) member is representative lightweight materials but its axial collapse mechanism is different from each other. The aluminum member absorbs energy by stable plastic deformation, while the CFRP member absorbs energy by unstable brittle failure with higher specific strength and stiffness than those in the aluminum member. Based on the respective collapse characteristics of CFRP side and aluminum members, the hybrid side members were tested on the axial collapse loads to get a synergy effect when the member is combined with the advantages of each members, such as energy absorption by the stable folding deformation of the aluminum member and by the high specific strength and stiffness of the CFRP member. Energy absorption capability and collapse mode of the hybrid side members were analyzed.

Abstract: In this study, the impact collapse tests were performed to investigate collapse characteristics of Al/CFRP member which were composed of aluminum members wrapped with CFRP (Carbon Fiber Reinforced Plastics) outside aluminum member. Aluminum members absorb energy by stable plastic deformation, while CFRP members absorb energy by unstable brittle failure with higher specific strength and stiffness than those in the aluminum member. In an attempt to achieve a synergy effect by combing the two members, Al/CFRP members were manufactured and impact collapse tests were performed for the members. Based on the respective collapse characteristics of aluminum and CFRP members, the collapse modes and energy absorption capability were analyzed for Al/CFRP member which have different fiber orientation angle of CFRP. Test results showed that the collapse of the Al/CFRP member complemented unstable brittle failure of the CFRP member due to ductile nature of the inner aluminum member and the fiber orientation angle of Al/CFRP members influence energy absorption capability and collapse mode.

Abstract: The front-end side members of automobiles, such as the hat-shaped section member, absorb the most of the energy during the front-end collision. The side members absorb more energy in collision if they have higher strength and stiffness, and stable folding capacity (local buckling). Using the above characteristics on energy absorption, vehicle should be designed light-weight to improve fuel combustion ratio and reduce exhaust gas. Because of their specific strength and stiffness, CFRP are currently being considered for many structural (aerospace vehicle, automobiles, trains and ships) applications due to their potential for reducing structural weight. Although CFRP members exhibit collapse modes that are significantly different from the collapse modes of metallic materials, numerous studies have shown that CFRP members can be efficient energy absorbing materials. In this study, the CFRP hat-shaped section members were manufactured using a uni-directional prepreg sheet of carbon/Epoxy and axial collapse tests were performed for the section members. The collapse mode and the energy absorption capability of the section members were analyzed under the static load.

Abstract: An aluminum or CFRP (Carbon Fiber Reinforced Plastics) tube is representative light-weight materials but its axial collapse mechamism is different from each other. The aluminum tube absorbs energy by stable plastic deformation, while the CFRP tube absorbs energy by unstable brittle failure with higher specific strength and stiffness than those in the aluminum tube. In an attempt to achieve a synergy effect by combining the two members, aluminum/CFRP square tubes were manufactured, which are composed of aluminum tubes wrapped with CFRP outside aluminum square tubes with different fiber orientation angle and thickness of CFRP, and axial collapse tests were performed for the tubes. The crushing behavior and energy absorption capability of the tubes were analyzed and compared with those of the respective aluminum square tubes and CFRP square tubes. Test results showed that the collapse of the aluminum/CFRP square tube complemented unstable brittle failure of the CFRP square tube due to ductile characteristics of the inner aluminum square tube. The collapse modes were categorized into four modes under the influence of the fiber orientation angle and thickness of CFRP. The absorbed energy per unit mass, which is in the light-weight aspect, was higher in the aluminum/CFRP square tube than that in the aluminum square tube or the CFRP square tube alone.