Bio-Based Trivalent Phytate:A Novel Strategy for Enhancing Fire Performance of Rigid Polyurethane Foam Composites

Biomass phytic acid has potential flame retardant value as the main form of phosphorus in plant seeds.In this study,phytate-based flame retardants aluminum phytate(PA-Al)and iron phytate(PA-Fe)were synthesized and characterized.Subsequently,they were introduced into rigid polyurethane foam(RPUF)as flame retardants by one-step water-blown method.The results indicated that RPUF/PA-Fe30 exhibited the highest char residue of 22.1 wt%,significantly higher than 12.4 wt%of RPUF.Cone calorimetry analysis showed that the total heat release(THR)of RPUF/PA-Al30 decreased by 17.0%and total smoke release(TSR)decreased by 22.0%compared with pure RPUF,which were the lowest,demonstrating a low fire risk and good smoke suppression.Thermogravimetric analysis-Fourier transform infrared spectrometer(TG-FTIR)implied the release intensity of flammable gases(hydrocarbons,esters)and toxic gases(isocyanate,CO,aromatic compounds,HCN)of composites was significantly reduced after the addition of PA-Fe.The analysis of char residue indicated that the RPUF composites formed a dense char layer with a high degree of graphitization after the addition of PA-Al/PA-Fe,endowing RPUF composites with excellent mass&heat transmission inhibition effect and fire resistance in the combustion process.

Optimization Design of Vibration Characteristics of Ship Composite Brace with Rigid Vibration Isolation Mass

In considering the theory of structural dynamic optimization design, a design method of the structural style of ship composite brace with rigid vibration isolation mass was studied. Two kinds of structural dynamic optimization formulations minimizing the vibration acceleration of the non-pressure hull on the restraining condition of the gross weight of the ship cabin were established: 1) dynamic optimization of the sectional dimensions of the rigid vibration isolation mass in the composite brace; 2) dynamic optimization of the arranging position of the rigid vibration isolation mass. Through the optimization results, sectional dimensions and the arranging position of the rigid vibration isolation mass with better performance in reducing vibration were gained, and some reference was provided for practical engineering designs as well as enrichment of the design method of a novel ship vibration-isolation brace.

Static behavior of semi-rigid thin-walled steel-concrete composite beam-to-column joints with bolted partial-depth flush end plate:experimental study

A new type of semi-rigid thin-walled steel-concrete composite beam-to-column joint has been proposed in this paper.Five semi-rigid composite beam-to-column joint specimens subjected to hogging moments under monotonic loading were tested to study the static behavior of this new type of joint.The main variable parameters for the five joint specimens were the longitudinal reinforcement ratio and the joint type.The experimental results designated that the magnitude of extension of the longitudinal reinforcement is the most important factor that influenced the moment-rotation characteristic of the new type of joint.The concrete slabs could resist 3.8%-19.1% of the total shear load applied to the cross-sections near the beam-to-column connection.The edge stiffened elements,such as the flange of the lipped I-section thin-walled steel beam,were capable of having considerable inelastic deformation capacity although they had comparatively large width-to-thickness ratios.The shear failure of the concrete cantilever edge strip must be taken into account in practical design because it has significant influence on the anchorage of the longitudinal reinforcement in the new type of external joints.

Study of the Bearing Capacity at the Variable Cross-Section of A Riser- Surface Casing Composite Pile

Reducing the cost of offshore platform construction is an urgent issue for marginal oilfield development.The offshore oil well structure includes a riser and a surface casing.The riser,surface casing and oil well cement can be considered special variable cross-section piles.Replacing or partially replacing the steel pipe pile foundation with a variable cross-section pile to provide the required bearing capacity for an offshore oil platform can reduce the cost of foundation construction and improve the economic efficiency of production.In this paper,the finite element analysis method is used to investigate the variable cross-section bearing mode of composite piles composed of a riser and a surface casing in saturated clay under a vertical load.The calculation formula of the bearing capacity at the variable section is derived based on the theory of spherical cavity expansion,the influencing factors of the bearing capacity coefficient N_(c) are revealed,and the calculation method of N_(c) is proposed.By comparing the calculation results with the results of the centrifuge test,the accuracy and applicability of the calculation method are verified.The results show that the riser composite pile has a rigid core in the soil under the variable cross-section,which increases the bearing capacity at the variable cross-section.

DYNAMIC ANALYSIS OF UNDERGROUND COMPOSITE STRUCTURES UNDER EXPLOSION LOADING

In selecting rational types of underground structures resisting explosion,in order to improve stress states of the structural section and make full use of material strength of each part of the section,the research method of composite structures is presented. Adopting the analysis method of micro-section free body,equilibrium equations,constraint equations and deformation coordination equations are given. Making use of the concept of generalized work and directly introducing Lagrange multiplier specific in physical meaning,the validity of the constructed generalized functional is proved by using variation method. The rational rigidity matching relationship of composite structure section is presented through example calculations.

Investigation of Mechanical Properties for Reinforced Polyester Composites with Palm Fronds

Natural fibers have become essential elements to produce composites, which have the renewability, sustainability, low cost and less health hazardous. Natural wastes improved the physical and mechanical properties of polyester-based composites. Reinforced polyester composites with natural fibers are spread widely in recent decades as an alternative to synthetics. This paper deals with effectiveness of palm fronds when they were added to a polyester. Percentage of palm fibers with respect to polyester is considered through present work. A Pin-on-disc tribometer has been used in experimental work under external forces, and the correlations of coefficient of friction have been used to make analysis of the experimental results. Ibertest universal testing machine was used to measure the tensile strength at a crosshead speed of 8 mm/min. The experimental analysis shows the improvement of properties of the used reinforced polyester, where, the results show that the highest values of coefficient of friction are 1.16667 for 5 N load and the lowest value is 0.55 for 9 N load. And the change for load 11 N is not significant. And also, 7.01 MPa is the highest value for tensile strength with the lowest value of modulus of rigidity 5.84 when the palm frond content is 3% and the lowest value of tensile test is 4.81 MPa with the highest value of modulus of rigidity 11.9 when 21% content.

Analysis of Vibrations of Roller of the Polymer Composite Coating Equipment on Stitches of Tarpaulin Materials

The article presents a structural diagram and the principle of operation of the installation of a sewing machine for applying a polymer composition to the stitch lines of tarpaulin materials. The calculation schemes and the mathematical model of oscillations of the axis of the composite roller during the application of the polymer composition along the lines of tarpaulin materials are presented. Based on the numerical solution of the problem, the regularities of roller oscillations are presented. The main parameters of the system are substantiated.

A comparative study on rigid and flexible magnetoelectric composites:Review

This review reports the latest trends in the ceramic composite matrix used for the magnetoelectric(ME)effect.In the last few years,ME composite has become the center of attraction for use in various electrically and magnetically coupled devices.The growth and use of electronic components everywhere have propulsively accelerated the exploration of self-powered electronic and sensor network devices.ME is a feasible technique for addressing difficulties of traditional batteries such as short life span and frequent recharge difficulties.Self-charging multiferroic components have been found for the constant working of mobile electronics that use multiferroic composites in response to magnetoelectric energy transformation.Researchers have rigorously studied the rigid and flexible magnetoelectric composites for their suitability in applications.This paper gives a comparative study between rigid and flexible magnetoelectric composites based on their properties and provides knowledge about the materials for such types of composites.It reviews the latest polymer-based ME materials as well as the related fabrication and polarization methods.The review finally encapsulates the applications in biomedicine,ranging from mechanical energy harvesters to sensors and actuators.

刚柔复合式路面结构与材料及发展趋势

刚柔复合式路面作为一种耐久性路面结构,广泛应用于重载交通、特殊地质条件、桥隧铺装等工程。为进一步推动耐久性刚柔复合式路面的应用,明确研究中的关键问题及发展方向,该文综述了国内外刚柔复合式路面的相关研究进展。在梳理刚柔复合式路面结构设计理论及施工技术的基础上,首先阐述了刚柔复合式路面的结构力学行为特征,分析了沥青面层和刚性基层的荷载应力、温度应力及其交互影响,刚性基层上的沥青面层一方面直接承受荷载和环境作用,另一方面可以改善下卧结构层的应力场和温度场,是影响刚柔复合式路面服役性能及使用寿命的关键;明确了刚柔复合式路面的病害主要出现在沥青面层,由于沥青面层与刚性基层之间的模量差异巨大,刚性基层上的沥青面层更倾向于产生压剪破坏,刚性基层的开裂以及刚‒柔层间的结合状态对沥青路面的性能也有着显著影响;最后,分别从沥青面层抗剪、基层板整体性、刚‒柔层间结合3个方面归纳了刚柔复合式路面性能的提升技术。基于刚柔复合式路面的结构力学特性,开展结构‒高性能材料一体化设计是提升刚柔复合式路面使用性能和耐久性的有效途径。

模块化建筑刚性桩复合地基共同作用试验分析

本文依据某模块化示范楼,制作了简化后的1∶10的模块化建筑刚性桩复合地基的室外缩尺模型,考虑了上部模块结构与地基基础共同作用。通过模型试验分析了上部模块刚度变化对上部模块钢柱、筏板基础和刚性桩复合地基各受力体的影响。结果表明:模块化建筑中部柱轴力>边部柱轴力>角部柱轴力;随上部模块刚度的增加,中部柱轴力逐渐减小,边部柱和角部柱轴力逐渐增大;筏板基础中部沉降最大,边部沉降最小,整体沉降随上部模块楼层的增加逐渐增大;角部桩身轴力>边部桩身轴力>中部桩身轴力,桩身轴力沿着桩深度方向先增大后减小;桩身上部一定范围内产生负摩阻力。分析结果能够为模块化建筑单元构件设计及刚性桩复合地基基础优化设计提供参考。

不均匀地层中刚性桩复合地基变形及加固措施分析

刚性桩复合地基凭借其工后沉降小、施工周期短、整体稳定性强、社会经济效益高等优势,逐渐得到广泛应用,但也伴随着一些工程问题,如在不均匀地层下刚性桩复合地基路堤容易出现稳定性问题。本文针对不均匀地层下刚性桩复合地基典型工程案例展开研究,采用有限元软件建立三维模型,揭示改进方案前后不均匀地层下刚性桩复合地基的变形规律,研究3种加固方式对于刚性桩复合地基稳定性的增强效果。结果表明:不均匀地层下刚性桩复合地基会产生偏应力进而引起路堤差异沉降,结构稳定性较差,改进方案可以有效降低路堤沉降,提高结构整体稳定性,横梁加固可以有效提高刚性桩复合地基的水平稳定性。

单向冻结下渠基土的锅盖效应试验研究

寒旱区刚柔复合衬砌渠道铺设的复合土工膜阻碍土体冻结过程中的水分蒸发,出现复合土工膜下土体增水的现象,即“锅盖效应”。为探究土体的锅盖效应发生机制和规律,制备不同含水率的土柱试样进行单向冻结试验,分析复合土工膜对土柱温度场和水分场的影响。研究表明:有复合土工膜覆盖土柱的降温速率及土层间温差均小于未覆盖复合土工膜的土柱;冻结过程中,未覆盖复合土工膜的土柱底部水分通过土体孔隙通道不断向顶层迁移补充后蒸发,整个土柱含水率降低,且呈不均匀状分布;而有复合土工膜覆盖的土柱,在水分迁移和锅盖效应作用下,底部土体含水率降低,膜下顶层土体含水率显著增加,且膜下结冰,表明复合土工膜使土体在冻结过程中产生明显的锅盖效应。初始含水率不同的土柱受锅盖效应影响后产生的水分迁移量和形态存在差异,初始含水率较小的土柱顶层含水率的增加以气态水迁移为主,初始含水率较大的土柱含水率的增加则以液态水迁移为主。

大跨梁-拱组合刚构桥船撞力和抗撞性能研究

梁-拱组合刚构桥是一种新桥型,船撞研究较少。该文以礼嘉嘉陵江大桥为工程背景,研究大跨度上承式梁-拱组合刚构桥梁的船撞力标准值和抗撞性能。首先确立了代表船型和船撞计算工况,利用ANSYS/LS-DYNA非线性有限元瞬态动力软件模拟了单墩模型在各工况下船桥碰撞过程,并对比了船撞力有限元仿真结果与多种经验公式计算结果。最后利用全桥模型和验算截面的极限承载力反推得到桥墩的极限抗船撞力,对桥墩的抗撞性能进行了评估。结果表明:船撞力具有很强的非线性波动特征,船艏最大撞深发生时刻滞后于最大撞击力发生时刻,船桥碰撞过程中的系统能量主要是由船舶动能转化为船艏局部变形内能;不同的船撞力经验公式的计算结果相差较大,推荐采用动力仿真模拟值;极限抗船撞力验算结果表明礼嘉嘉陵江大桥主墩的抗撞性能满足要求。

刚性桩复合地基的载荷试验问题

《建筑与市政地基基础通用规范》(GB 55003—2021)对刚性桩复合地基承载力验收的条文是:复合地基承载力的验收检验应采用复合地基静载荷试验,对有粘结强度的复合地基增强体尚应进行单桩静载荷试验。在实际工程中,可能会遇到这样的情况:(1)复合地基静载荷试验合格,单桩静载荷试验不合格,复合地基承载力真的不合格吗?(2)复合地基和单桩静载荷试验都合格,复合地基承载力就一定合格吗?本文对此进行了分析讨论,认为与地质条件有关,规范方法主要是针对单一均匀地基的情况,对于多层土地基,规范方法有局限性,由于试验压板尺寸小,压板试验还不能反映深层土的影响。对于大尺寸的基础,还要进行科学的分析,应对实际尺寸的基础沉降进行计算分析,才能判断和保证工程的安全,仅靠小尺寸的压板载荷试验是不够完善的。

连续刚构箱形-双薄壁组合式主墩及其刚度匹配设计方法

文章针对因受到建设条件制约而不得不采用主墩高度相差较大的连续刚构桥梁,应用箱形-双薄壁组合式桥墩作为主墩结构,提出了对应的主墩刚度匹配设计方法,并对刚度计算过程进行了推导,得到了组合式桥墩墩顶顺桥向抗推集成刚度的计算公式,用实桥计算示例对提出的主墩设计和传统设计的结果进行了对比。结果表明,文章提出的箱形-双薄壁组合式主墩刚度匹配设计方法能有效地避免主墩高度差引起的内力不均匀分配问题,从而改善高、低主墩连续刚构桥梁在温度、制动力等水平荷载下的力学表现,提高结构的抗震性能。

基于光谱学分析的硬质聚氨酯泡沫/钢渣/次磷酸铝复合材料阻燃机理研究

硬质聚氨酯泡沫(RPUF)的优异性能使其在各领域被广泛应用,但本身的易燃性为其在应用过程中埋下了巨大的安全隐患。钢渣(SS)作为提炼铁精矿后排放的固体废弃物,因其综合利用效率低下而造成一系列环境污染问题。为提高RPUF火灾安全性和钢渣的附加值,将SS和次磷酸铝(AHP)引入到RPUF中,采用一步全水发泡法,制备一系列阻燃RPUF(FR-RPUF)复合材料。利用射线荧光光谱分析(XRF)探究了SS的化学成分,并系统研究了SS/AHP对FR-RPUF复合材料的微观形貌、热稳定性、阻燃性能以及气相产物的影响。XRF测试表明:钢渣的化学成分主要是CaO、SiO_(2)、Al_(2)O_(3)、Fe_(2)O_(3)、SO_(3)、MgO,以上金属氧化物能够作为协效剂促进聚合物成炭,并覆盖在材料表面阻隔燃烧热,在凝聚相达到阻燃目的。扫描电镜(SEM)测试表明:SS/AHP与RPUF基体的相容性较差导致FR-RPUF的泡孔出现不同程度的破损。阻燃测试表明:RPUF-1、RPUF-4、RPUF-5的极限氧指数分别为24.2 vol%、23.4 vol%、19.7 vol%,说明SS和AHP存在一定的协效阻燃作用,且RPUF/SS/AHP复合材料全部通过UL-94 V-0级别,满足外墙保温材料使用要求。热重-红外分析(TG-FTIR)测试表明:SS/AHP并未改变RPUF的降解过程,气相产物主要为碳氢化合物、羰基化合物、氨基甲酸酯、CO_(2)、异氰酸酯化合物、芳香族化合物、氰化氢、羰基化合物和酯类。对典型挥发性产物进一步分析发现,AHP和SS的加入促进RPUF基体早期降解。拉曼测试表明:当SS/AHP加入到RPUF后,RPUF-4的D峰与G峰的峰面积比(I_(D)/I_(G))值最小,表明SS/AHP的加入提高了FR-RPUF复合材料炭渣的致密性、石墨化程度。结合上述分析提出阻燃机理:首先AHP吸热分解,降低了火焰周围的温度,其分解的PO·自由基捕获游离的HO·抑制连锁反应,分解产生的焦磷酸铝与炭渣覆盖在基体表面,抑制了火焰和可燃气体的扩散。AHP分解产生的PH3遇氧气生成酸性物质(磷酸和聚磷酸),促进了RPUF脱水成炭,并且钢渣中的矿物成分会与磷酸或聚磷酸反应,形成致密炭层,与AHP共同发挥协效阻燃作用。研究为SS和AHP复配阻燃硬质聚氨酯泡沫材料提供理论依据和实验基础。

铜尾矿/聚磷酸铵阻燃聚氨酯的制备及研究

以聚磷酸铵(APP)/铜尾矿(CTS)为阻燃体系,采用一步全水发泡法制备硬质聚氨酯泡沫/聚磷酸铵/铜尾矿(RPUF/APP/CTS)复合材料。阻燃测试表明,RPUF-30APP的极限氧指数(LOI)达到24.0%,垂直燃烧测试达到V-0级别,其阻燃性明显提高。锥形量热测试表明,RPUF-30APP的热释放速率峰值(PHRR)由纯样的300.5 kW/m^(2)降低至139.4 kW/m^(2),下降幅度高达53.6%;总热释放(THR)由纯样的40.0 MJ/m^(2)下降至28.1 MJ/m^(2),降低幅度高达29.8%,表明APP/CTS体系明显降低复合材料燃烧过程中的热释放,其火灾安全性提高。炭渣分析表明,CTS/APP/RPUF复合材料燃烧过程中形成了致密的炭层,提高了复合材料的阻燃性能。该研究为CTS提供了一个新的应用领域,并为提高聚合物的防火安全性铺平了道路。

Behavior of composite rigid frame bridge under bi-directional seismic excitations

Pushover analysis and time history analysis are conducted to explore the bi-directional seismic behavior of composite steel-concrete rigid frame bridge, which is composed of RC piers and steel-concrete composite girders. Both longitudinal and transverse directions excitations are investigated using OpenSees. Firstly, the applicability of pushover analysis based on the funda- mental mode is discussed. Secondly, an improved pushover analysis method considering the contribution of higher modes is proposed, and the applicability on composite rigid frame bridges under bi-directional earthquake is verified. Based on this method, an approach to predict the displacement responses of composite rigid frame bridge under random hi-directional seismic excitations by revising the elasto-plastic demand curve is also proposed. It is observed that the developed method yield a good estimate on the responses of composite rigid frame bridges under bi-directional seismic excitations.

硬质聚氨酯泡沫/EG/MPP复合材料的制备及阻燃性能

将三聚氰胺聚磷酸盐(MPP)与可膨胀石墨(EG)进行复配,并采用一步法全水发泡法制备了硬质聚氨酯泡沫/可膨胀石墨/三聚氰胺聚磷酸盐(RPUF/EG/MPP)复合材料。在此基础上,采用热重分析(TG)、阻燃测试、微型量热(MCC)、扫描电镜(SEM)系统研究RPUF/EG/MPP复合材料的热稳定性、阻燃性、燃烧特性和炭渣微观形貌。研究表明,EG和MPP的加入可以明显提高RPUF/EG/MPP复合材料的热稳定性,40.6份MPP和20.3份EG的加入使得RPUF-2在800℃时,残炭率高达31.7%。阻燃测试表明,MPP和EG之间存在协效阻燃作用,其最大极限氧指数可达29.9%。微型量热测试表明,MPP和EG的加入可以有效降低RPUF复合材料燃烧过程中的热释放,提升其火灾安全性能。

舰船复合材料轴振动能量传递特性研究

针对舰船复合材料传动轴减振机理尚不清晰的问题,文中构建了某舰船复合材料轴仿真模型,基于功率流法分析了复合材料轴振动能量传递特性,并在此基础上进一步探究了钢法兰-复合材料刚柔耦合界面匹配参数和轴段内复合材料铺层方式对振动能量传递的影响规律。最后通过复合材料传动轴模态试验和振动传递试验验证了仿真模型的准确性。结论如下:刚柔耦合界面对于振动能量抑制有着显著作用,其振动能量的传递随接触面积的增大而降低,而弹性模量比仅影响传动轴固有频率;随着铺层角度的减小及铺层数量的增加,复合材料轴段隔振性能逐渐增加。