Hybrid S2/Carbon Epoxy Composite Armours Under Blast Loads

Civil and military structures, such as helicopters, aircrafts, naval ships, tanks or buildings are susceptible to blast loads as terroristic attacks increases, therefore there is the need to design blast resistant structures. During an explosion the peak pressure produced by shock wave is much greater than the static collapse pressure. Metallic structures usually undergo large plastic deformations absorbing blast energy before reaching equilibrium. Due to their high specific properties, fibre-reinforced polymers are being considered for energy absorption applications in blast resistant armours. A deep insight into the relationship between explosion loads, composite architecture and deformation/fracture behaviour will offer the possibility to design structures with significantly enhanced energy absorption and blast resistance performance. This study presents the results of a numerical investigation aimed at understanding the performance of a hybrid composite (glass/carbon fibre) plate subjected to blast loads using commercial LS-DYNA software. In particular, the paper deals with numerical 3D simulations of damages caused by air blast waves generated by C4 charges on two fully clamped rectangular plates made of steel and hybrid (S2/Carbon) composite, respectively. A Multi Materials Arbitrary Lagrangian Eulerian (MMALE) formulation was used to simulate the shock phenomenon. For the steel plates, the Johnson-Cook material model was employed. For the composite plates both in-plane and out-of-plane failure criteria were employed. In particular, a contact tiebreak formulation with a mixed mode failure criteria was employed to simulate delamination failure. As for the steel plates the results showed that excellent correlation with the experimental data for the two blast load conditions in terms of dynamic and residual deflection for two different C4 charges. For the composite plates the numerical results showed that, as expected, a wider delamination damage was observed for the higher blast loads case. Widespread tensile matrix damage was experienced for both blast load cases, while only for 875?g blast load fiber failure damage was observed. This agrees well with the experimental data showing that the composite panel was not able to resist to the 875?g blast load.     

Experimental and numerical study of composite lightweight structural insulated panel with expanded polystyrene core against windborne debris impacts

Natural disasters such as cyclone, hurricane, tornado and typhoon cause tremendous loss around the world. The windborne debris usually imposes high speed localized impact on the building envelope, which may harm people inside the building and create dominant openings. A dominant opening in the building envelope might cause internal pressure increasing and result in substantial damage to the building structures, such as roof lifting up or even collapse. To withstand the impact of such extreme event, the penetration resistant capacity of wall or roof panels to windborne debris impact should meet the requirements specified in the wind loading codes, e.g., the Australian Wind Loading Code (AS/NZS 1170.2:2011). In this study, a composite Structural Insulated Panel (SIP) with Extended Polystyrene (EPS) core sandwiched by flat metal skins that is commonly used in building industry was investigated. To study the structural response and penetration resistant capacity of the composite panel against windborne debris impacts, a series of laboratory tests were carried out by using a pneumatic cannon testing system. The effects of various specimen configurations, impact locations and debris impact velocities on their performance were investigated. The failure modes under various projectile impact scenarios were observed and compared by using two high-speed cameras. The dynamic responses were examined quantitatively in terms of the opening size, residual velocity of projectile, deformation and strain time histories on the back skin measured in the tests. The penetration resistance capacity of the panels subjected to windborne debris impact were examined and analyzed. In addition, numerical models were developed in LS-DYNA to simulate the response and damage of the composite SIP under windborne debris impact. Laboratory tested panels were first modeled. The test data was used to calibrate the accuracy of the numerical model. The validated numerical model was then used to conduct more numerical simulations to obtain more results such as energy absorption, impact force and vulnerability curve of the SIP against windborne debris impact.     

Experimental study on hybrid CFRP-PU strengthening effect on RC panels under blast loading

Recently, fiber reinforced polymer (FRP) usages for strengthening RC infrastructures have been continuously increasing. Especially, the use of FRPs to strengthen structures against a blast terror or an impact accident is receiving great interests from specialists in the structural retrofitting and strengthening field. In order to achieve better protections from blast or impact loading, a new retrofit composite material has been proposed by combining highly stiff and strong material of carbon fiber reinforced polymer (CFRP) with highly ductile material of Polyurea (PU). The combination of CFRP and PU can result in a retrofit composite with enhanced stiffness and ductility properties as well as fragment catching characteristic. To estimate the hybrid composite’s blast resistant capacity, nine 1000 × 1000 × 150 mm RC panel specimens retrofitted with either CFRP, PU, or hybrid composite sheets were blast tested. The blast load was generated by detonating a 15.88 kg ANFO explosive charge at 1.5 m standoff distance. The data of free field incident and reflected blast pressures, maximum and residual displacements, and steel and concrete strains, etc. are measured from the test. Also, the failure mode and crack patterns were evaluated to determine the failure characteristic of the panels. The results from the experiments showed that the hybrid composite has better blast resistant capacity than ordinary retrofit FRPs. The study results are discussed in detail in the paper. The test results will not only provide blast resistant capacity of each retrofit material, but they will be valuable backup data for preliminary estimation of RC structural members’ blast protection performances.     

水下冲击波作用的铝合金蜂窝夹层板动力学响应研究

为研究铝合金蜂窝夹层板水下爆炸冲击波载荷作用的动态响应及抗冲击性能,利用非药式水下爆炸冲击波加载装置对气背固支5A06铝合金夹层板及具有相同面密度的单层板进行水下冲击波加载试验。利用高速相机结合三维数字散斑技术(DIC)对夹层板后面板动态响应进行实时测量,获得夹层板气背面受水下冲击波作用的动态响应历程及变形毁伤模式,比较分析铝合金蜂窝夹层板抗冲击防护性能。结果表明,较相同面密度的单层板,蜂窝夹层板受水下冲击波载荷作用的芯层压缩能有效减少气背面板的塑性变形,提高夹层结构整体抗冲击性能。     

POZD涂层对防护门抗冲击性能影响研究

聚异氰氨酸酯噁唑烷酮(polyisocyanateoxazodone,POZD)是一种弹性材料,可以在结构表面形成高强度和高弹性涂层,具有减轻不同结构冲击和爆炸的潜力.为研究POZD作为涂层时梁板式钢结构防护门的抗冲击性能,采用数值模拟方法对该门扇在6级载荷作用下的动态响应过程进行研究,分析面板厚度、工字钢型号变化时对...     

Analysis of a bridge collapsed by an accidental blast loads

Analysis of the structural failure of a bridge caused by an accidental fireworks explosion is presented in this paper. The equivalent mass of TNT due to the fireworks explosion and the structural response of the bridge due to the dynamic load imposed by the explosion are modeled by engineering algorithms and numerical simulations. Analysis confirmed that bridge failure occurred due to the blast load and there was no inherent design defect. The results of this investigation are relevant towards understanding future events wherein a dynamic load might be accidentally applied to fixed structures.     

Damage prediction of concrete gravity dams subjected to underwater explosion shock loading

The damage prediction of concrete gravity dams under blast loads has gained importance in recent years due to the great number of accidental events and terrorist bombing attacks that affected engineering safety. It has long been known that an underwater explosion can cause significantly more damage to the targets in water than the same amount of explosive in air. While the physical processes during an underwater explosion and the subsequent response of structures are extremely complex, which involve lots of complex issues such as the explosion, shock wave propagation, shock wave-structure interaction and structural response. Hence a sophisticated numerical model for the loading and material responses would be required to enable more realistic reproduction of the underlying physical processes. In this paper, a fully coupled numerical approach with combined Lagrangian and Eulerian methods, incorporating the explosion processes, is performed. The RHT (Riedel–Hiermaier–Thoma) model including the strain rate effect is employed to model the concrete material behavior subjected to blast loading. Detailed numerical simulation and analysis of a typical concrete gravity dam subjected to underwater explosion are presented in this study. In terms of different TNT charge weights, the structural response and damage characteristics of the dam at different standoff distances are investigated. Based on the numerical results, critical curves related to different damage levels are derived.     

化爆作用下FRP加固RC板的试验研究及动力响应分析

我国20世纪60年代、70年代修建的大量防护工程抗力等级较低,急需进行加固补强。进行了化爆作用下,外贴FRP条带加固钢筋混凝土(RC)双向板抗爆性能的试验研究。按介质-结构相互作用理论确定结构的爆炸冲击荷载,建立了加固板的三折线弯曲抗力模型,利用虚功原理建立了加固RC板的运动微分方程,按数值方法求解了外贴FRP加固双向板在化爆冲击波作用下的动力响应时程,分析结果与试验结果吻合较好。研究结果表明:外贴FRP条带加固可以有效延缓混凝土的开裂、限制裂缝的开展,提高RC双向板的刚度,减小结构位移,减轻结构破坏程度,外贴FRP加固RC双向板的抗爆炸冲击波能力得到了明显提高,外贴FRP条带在极限状态时发生了剥离破坏和断裂破坏。     

Application of a coupled Eulerian–Lagrangian method to simulate interactions between deformable composite structures and compressible multiphase flow

Interactions between deformable composite structures and compressible multiphase flow are common for many marine/submarine problems. Recently, there has been an increased interest in the application of composite structures in marine industry (e.g. propulsion system, ship hulls, marine platforms, marine turbines, etc) to take advantage their high stiffness to weight and strength to weight ratios, and high impact/shock resistance characteristics. It is therefore important to evaluate the performance of composite structures subject to dynamic loads. In this paper, a coupled Eulerian–Lagrangian numerical method is proposed to model the two‐dimensional (2D) or axisymmetric response of deformable composite structures subject to shock and blast loads. The method couples an Eulerian compressible multiphase fluid solver with a general Lagrangian solid solver using an interface capturing method, and is validated using analytical, numerical, and experimental results. A 2D case study is shown for an underwater explosion beneath a three‐layered composite structure with clamped ends. The importance of 2D fluid–structure interaction effects on the transient response between composite structures and compressible multiphase flow is discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

Blast impact response of aluminum foam sandwich composites

Military and civilian structures can be exposed to intentional or accidental blasts. Aluminum foam sandwich structures are being considered for energy absorption applications in blast resistant cargo containers, ordnance boxes, transformer box pads, etc. This study examines the modeling of aluminum foam sandwich composites subjected to blast loads using LS-DYNA software. The sandwich composite was designed using laminated face sheets (S2 glass/epoxy and aluminum foam core. The aluminum foam core was modeled using an anisotropic material model. The laminated face sheets were modeled using material models that implement the Tsai-Wu and Hashin failure theories. Ablast load was applied using the CONWEP blast equations (*LOAD_BLAST) in LS-DYNA. This paper discusses the blast response of constituent S2-glass/epoxy face sheets, the closed cell aluminum foam core as well as the sandwich composite plate.     

“Collapsible” lightweight aggregate concrete. Part II: characterization under static and dynamic loadings

In this work a granular cementitious composite has been developed, tailoring its performance to a low compressive strength and high deformation and energy dissipation capacity, which can be required to the material when employed in post-installed screeds for protection of structures and infrastructures against accidental actions such as impact and blast. The required level of performance can be achieved by uniform grain size distribution, paste content as low as minimum theoretical void ratio and low paste strength: it is believed that the synergy between the aforementioned three requirements can allow for energy dissipation capacity after paste cracking due to both rearrangement of grain meso-structure and, in case, grain crushing. After the mix design concept and optimization of the material composition, illustrated in the first part of this companion paper study, the mechanical performance of the composite under static and impact compressive loadings has been thoroughly characterized, as affected by mix-design variables, such as paste volume fraction, water to cement ratio and aggregate size. The reliability will thus be thoroughly checked, of the employed material concept, and the influence will also be investigated, if any, of specimen shape, size and boundary conditions.     

Experimental and computational investigations on fire resistance of GFRP composite for building façade

Composite materials such as glass fibre reinforced polymers (GFRPs) possess the advantages of high strength and stiffness, as well as low density and highly flexible tailoring; therefore, their potential in replacing conventional materials (such as concrete, aluminium and steel) in building façade has become attractive. This paper addresses one of the major issues that hinder the extensive use of composite structures in the high-rise building industry, which is the fire resistance. In this study, a fire performance enhancement strategy for multilayer composite sandwich panels, which are comprised of GFRP composite facets and polyethylene foam core, is proposed with the addition of environmentally friendly, fire retardant unsaturated polyester resins and gel-coats. A series of burning experimental studies including thermo-gravimetric analysis (TGA) and single burning item (SBI) are carried out on the full scale composite sandwich as well as on single constituents, providing information regarding heat release rate, total heat release, fire growth rate, and smoke production. Experimental results are compared with fire safety codes for building materials to identify the key areas for improvements. A fire dynamic numerical model has been developed in this work using the Fire Dynamics Simulator (FDS) to simulate the burning process of composite structures in the SBI test. Numerical results of heat production and growth rate are presented in comparison with experimental observations validating the computational model and provide further insights into the fire resisting process. Parametric studies are conducted to investigate the effect of fire retardant additives on the fire performance of the composite sandwich panel leading to optimum designs for the sandwich panel.     

组合楼板钢框架结构的连续倒塌简化模拟

该文借助经过校验的组合楼盖精细模型,建立了组合楼板钢框架结构连续倒塌有限元简化模型,通过与组合楼盖子结构试验对比验证了此简化模型的准确性。采用简化模型,分析了柱子失效位置、结构层数和组合楼板等参数对一个五层组合楼板钢框架原型结构抗连续倒塌性能的影响。分析结果表明：原型结构具有足够的承载力以避免由单个底层柱子失效所导致的结构连续倒塌;除了角柱失效工况外,原型结构的层数变化对结构抗连续倒塌性能的影响可以忽略,而在角柱失效工况下,层间桁架承载机制的贡献会使得原型结构比单层有楼板结构的抗连续倒塌承载力更高;在考虑组合楼板之后,原型结构的抗连续倒塌承载力提升了114%。     

绿色装配式钢结构建筑体系研究与应用

发展钢结构建筑,可化解钢铁产业过剩产能,推进建筑绿色化、工业化、信息化。在国家政策推动下,我国装配式钢结构建筑从1.0时代快速迈向2.0时代,发展了以传统钢结构形式为基础的改进型建筑体系,模块化新型建筑体系和工业化住宅建筑体系。新形势下,预制混凝土构件解决了钢结构的传统难题,不同墙体交叉应用发展了新型围护系统,信息化技术促进了建筑业跨越式发展。全装配钢框架和盒子型模块化装配体系是新型低、多层模块化建筑体系,其采用“建筑元器件”的设计概念,以结构构件或建筑功能单元为基本元件组合而成,具有构件装配化、围护一体化、生产工厂化等特点。新型MCFTS（Multi-core Concrete Filled Steel Tube System）高层钢结构体系适用于住宅建筑和公共建筑,该体系分为组合多腔钢管混凝土框架-支撑住宅体系和组合多腔钢板墙核心筒-钢管混凝土框架公共建筑体系。MCFTS体系以组合多腔扁柱和双侧板连接节点为技术核心。研究结果表明,该体系具有优良的抗震性能和可修复性能。     

Design of Composite Wing Access Cover Under Impact Loads

The paper describes a design concept and prototype development study for a composite wing access cover panel which may be subjected to high velocity impact loads from burst tyre fragments. A number of design variants were fabricated in unidirectional (UD) carbon fibre reinforced polyetheretherketone (CF/PEEK) using the vacuum forming method. Emphasis in the paper is on the use of impact simulations at the design stage to assess various design concepts for the composite panel using finite element (FE) simulation techniques. These predict a damage state in the structure after impact loading, which allows the panel concepts to be ranked for impact resistance. This led to a successful design concept, which was verified by structural impact tests, in which the CF/PEEK access panel had an impact resistant liner of high performance polyethylene fabric.     

Blast response of cracked steel box structures repaired with carbon fibre-reinforced polymer composite patch

In this paper the blast resistance of cracked steel structures repaired with fibre-reinforced polymer (FRP) composite patch are investigated. The switch box which has been subjected to blast loading is chosen to study. The steel material is modelled using isotropic hardening model, pertaining to Von Mises yield condition with isotropic strain hardening, and strain rate-dependent dynamic yield stress based on Cowper and Symonds model. Three different cracked structures are chosen to investigate their capability in dissipating the blast loading. To improve the blast resistance, the cracked steel structures are stiffened using carbon fibre-reinforced polymer (CFRP) composite patches. The repaired patches reduce the stress field around the crack as the stress is transferred from the cracked zone to them. This situation prevents the crack from growing and extends the service life of the steel structure. It will be shown that CFRP repairing can significantly increase the blast resistance of cracked steel structures.     

建筑物防汽车炸弹工程措施

汽车炸弹袭击作为恐怖活动中最常见和危害最大的一种方式,具有行动隐蔽、发起突然、危害性大的特点,已经引起世界各国的广泛关注.结合目前国内外在建筑物防爆抗爆研究领域的最新研究成果,详细介绍了防爆路障、防爆墙的定型产品及作用原理,总结了结构构件的加固措施,提出了防汽车炸弹工程措施体系.     

框支密肋复合墙结构地震易损性研究

地震易损性分析通过概率计算建立地震强度和结构损伤之间的关系，可以实现结构地震风险预测和评估。为了对框支密肋复合墙结构在不同地震强度下的抗震能力进行评估，该文采用OpenSEES有限元软件，选用密肋复合墙的刚架-等效斜撑简化模型，建立结构整体分析模型，基于增量动力时程分析(IDA)和易损性分析，研究不同参数的变化对结构抗震性能的影响。结果表明：转换层刚度比的变化对结构性能影响显著，结构竖向布置均匀对抗震有利，建议8度区框支密肋复合墙结构的刚度比取值为1.0～2.5；肋柱数量、砌块强度的变化可对结构的抗震性能产生影响，应合理选择；混凝土强度等级对结构的抗震性能影响较大，在实际应用中应在满足规范要求的前提下选择较大的混凝土强度等级。     

Disaster of an industrial hall caused by an explosion of wood dust and fire

This article scrutinises a disaster affecting an industrial hall built of prefabricated reinforced concrete. As a result of an explosion of technological equipment used in the woodworking process, the entire pretensioned prestressed concrete girder structure, as well as the roof slabs, was badly damaged. Additional damage was caused by the high temperature generated by the resultant fire, as well as rapid cooling due to fire-fighting activities. Increased air pressure and the ensuing shock wave caused extensive damage to the brick walls in the neighbouring technology rooms. The explosion caused deformations of a brick chimney located more than 100 m from the blast zone. Subsequent investigations showed that a lack of adhesion of the tension members in the contact zone with an incoherent concrete structure could have led to a complete destruction of the covering structure. In the degraded girders located directly above the explosion area, a gradual loss of the prestressing force was observed. To prevent spreading of the disaster, ad hoc operations to protect both the structure of the building and the remaining technological equipment were developed. The girders located directly in the explosion zone were temporarily propped up and prepared for immediate removal. The article also presents an account of the reconstruction of the damaged building. In place of the removed prestressed girders, a light cover supported on truss steel girders was designed. The investigations that followed confirmed that an immediate cause of the hall’s damage was destructive processes triggered by the self-ignition of a mixture of wood dust in the improperly ventilated wood processing machinery. The resultant flame brought about a secondary explosion of the dust accumulated in the hall. The lack of proper human supervision of the industry control systems additionally increased the extent of the damage and financial losses.     

碳纤维铝蜂窝夹芯复合结构隔声性能研究

铝蜂窝夹芯复合结构在航空工业、高速列车及汽车车体中得到越来越多的应用,其隔声性能对车内及机舱噪声有重要影响。建立了碳纤维铝蜂窝夹芯复合结构有限单元模型,用有限单元法计算了结构在声载荷激励下的响应,并计算分析了复合结构的隔声性能,分析了碳纤维复合面板厚度、面板层数、铺设角度、铝蜂窝芯层的厚度、铝蜂窝壁厚对隔声性能的影响。研究结果表明,面板采用碳纤维复合结构时,在小于1 000 Hz的低频段,相同面板厚度的铝蜂窝复合结构隔声性能比全铝合金材料的铝蜂窝夹芯复合结构有所降低,而且在高频段会出现隔声量更低的隔声低谷;相较于铝合金面板,复合结构的面板采用碳纤维复合材料时,能够实现整体结构轻量化也提高复合结构的隔声性能;各层之间按相对90°铺设时复合结构隔声性能最好;随着面板厚度的增加复合结构隔声性能增加,面板层总厚度不变的情况下,单层面板或者过多的层数都会使复合结构隔声性能降低。