Influence of winding angle on the strength and deformation of filament-wound composite tubes subjected to uniaxial and biaxial loads

Experimental data are presented to show the effects of winding angle on the strength of 100 mm diameter, 1 mm thick, filament wound E-glass fibre reinforced epoxy resin tubes tested under various combinations of internal pressure and axial tension or compression. Leakage and fracture strength envelopes are presented for ±45°, ±55° and ±75° winding angle tubes subjected to a wide range of different biaxial membrane stress states. Strengths range from 30 to 1250 MPa. Axial compression test results for tubes with wall thicknesses ranging from 1 to 3·6 mm establish the influence of shell buckling. Stress/strain curves up to fracture under three different types of loading show the effects of the winding angle on elastic constants and on nonlinear stress strain behaviour.     

含孔CFRP正交层合板的双轴拉伸力学行为

采用加载臂开槽的中心开孔等厚度十字形试样,实验研究了正交对称铺层碳纤维增强聚合物基复合材料（CFRP）层合板在双轴拉伸载荷作用下的力学行为,分析了3种双轴加载比对其拉伸强度和破坏行为的影响。研究表明:纤维被切断的铺层部分在拉伸作用下容易与其相邻铺层脱粘,导致层合板承载力下降;等双轴加载时,在孔边的被切断纤维与连续纤维间基体在横向拉伸和纵向剪切组合作用下首先开裂;非等双轴加载时,在垂直于快速拉伸方向的铺层中沿孔边应力集中处先出现基体裂纹;随着加载比的增大,快速拉伸方向的细观结构损伤随载荷的增大发展更快,刚度下降更快,破坏时主裂纹的扩展方向更趋于垂直于快速拉伸方向;强度包络线的分析表明快速拉伸方向的拉伸强度随加载比的增大呈缓慢增大的趋势。      

The rate-dependent behaviour of ± 55 ° filament-wound glass-fibre/epoxy tubes under biaxial loading

This paper presents the results of an experimental investigation into the behaviour of glass-fibre-reinforced epoxy tubes subjected to monotonic biaxial loading. Commercially available tubes with a filament winding pattern of ± 55 ° were tested in a biaxial testing machine with various ratios of axial stress to hoop stress. In addition, the tubes were tested at three rates of monotonic loading. The resulting stress/strain curves were analyzed and biaxial failure envelopes in terms of stress and strain were constructed demonstrating the complexity of the behaviour of the tubes. It is shown that the rate and ratio of biaxial loading affect the monotonic failure strength, damage accumulation and the mode of failure. In addition, these results are discussed based on macro and micro observations of damage and failure modes.     

基于弹塑性损伤本构模型的复合材料层合板破坏荷载预测

在连续损伤力学和塑性力学框架内,建立一个同时考虑塑性效应和损伤累积导致材料属性退化的复合材料弹塑性损伤本构模型。基于最近点投影回映算法,开发本构模型的应变驱动隐式积分算法以更新应力及与解答相关的状态变量,并推导与所开发算法相应的数值一致性切线刚度矩阵,保证有限元分析采用NewtonRaphson迭代法解答非线性问题的计算效率。采用断裂带模型对已开发的本构模型软化段进行规则化,以减轻有限元分析结果的网格相关性问题。对损伤变量进行粘滞规则化,并推导出相应的粘滞规则化数值一致性切线刚度张量,解决了在有限元隐式计算程序中采用含应变软化段本构关系的数值分析由于计算困难而提前终止的问题。开发包含数值积分算法的用户材料子程序UMAT,并嵌于有限元程序Abaqus v6.14中。通过对力学行为展现显著塑性效应的AS4/3501-6V型开口复合材料层合板的渐进失效分析,验证本文提出的材料本构模型的有效性。结果显示,预测结果与已报道的试验结果吻合良好,并且预测精度高于其他已有弹性损伤模型。表明已建立的弹塑性损伤本构模型能够准确预测力学行为,展现显著塑性效应的复合材料层合板的破坏荷载,为其构件和结构设计提供一种有效的分析方法。     

Failure analysis of fiber-reinforced composite laminates subjected to biaxial loads

A nonlinear constitutive model for a single lamina is proposed for the failure analysis of composite laminates. In the material model, both fiber and matrix are assumed to behave as elastic-plastic and the in-plane shear is assumed to behave nonlinearly with a variable shear parameter. The damage onset for individual lamina is detected by a mixed failure criterion, composed of the Tsai-Wu criterion and the maximum stress criterion. After damage takes place within the lamina, the fiber and in-plane shear are assumed to exhibit brittle behavior, and the matrix is assumed to exhibit degrading behavior. The proposed nonlinear constitutive model is tested against experimental data and good agreement is obtained. Then, numerical analyses are carried out to study the failure behavior of symmetric angle-ply composite laminates and symmetric cross-ply composite laminates subjected to biaxial loads. Finally, the conclusions obtained from the numerical analysis are given.     

Behaviour of steel-fibre-reinforced concretes under biaxial compression loads

In the case of metal fibre concretes under biaxial compression, the gain of strength yielded by metal fibres can be considerable. Using a biaxial press with brush bearing platens (to avoid lateral confinement), we verified this result and studied the behaviour of metal fibre concrete subjected to biaxial loadings. Two different types of fibres were used. The results obtained demonstrate the following points: the addition of fibres makes the material much more ductile; there is an influence of the type of fibre on mode of failure, a gain of strength and an influence of the orientation of the fibres.     

三维机织碳/碳复合材料双轴压缩载荷下的力学行为

基于三维机织碳/碳复合材料的细观结构特征, 设计平板十字形试样, 在材料双轴力学性能试验机上开展了复合材料单轴、 双轴加载压缩试验, 对比分析了三维机织碳/碳复合材料在双轴压缩载荷下的力学行为。研究表明: 三维机织碳/碳复合材料的压缩行为表现为非线性、 脆性断裂; 双轴载荷作用下非线性特征更为显著, 压缩模量随应力的增加而增大, 强度与模量相较于单轴有较大幅度增加, 双轴压缩载荷作用下材料的强化效应显著; 试样破坏位置并未出现在试样中心区, 而是发生在试样的加载端部或十字形试样的加载分枝根部, 主要表现为基体开裂、 纤维断裂和层间脱粘, 碳布及其层间界面剪切强度的强弱直接影响材料的压缩强度。     

自密实轻集料混凝土双轴受力力学性能

为探究自密实轻集料混凝土双轴力学性能,采用三轴试验机对其进行双轴压-压和双轴拉-压试验,得到不同工况下的应力-应变曲线及其破坏形态,通过提取应力-应变曲线峰值应力和峰值应变,并与相关文献普通混凝土与轻集料混凝土研究成果对比,分析自密实轻集料混凝土双轴力学性能。研究结果表明:双轴压-压工况下,当侧向压应力较低时,试件主要呈现剪切破坏形态;当侧向应力较高时,试件呈劈裂破坏形态。双轴拉-压工况下,试件主要呈劈拉破坏形态,与侧向应力无关。随着侧向压应力的提高,自密实轻集料混凝土主压应力相对比无侧向应力工况明显提高,峰值应力最大提高均值幅度为68.08%,主拉应力随侧向压应力的提高逐步降低,最大降低幅度为62.35%。应用Kupfer双轴受力破坏准则验证自密实轻集料混凝土受侧向应力影响变化规律较为保守,同时基于Kupfer提出自密实轻集料混凝土双轴力学性能破坏准则,所得到的破坏准则方程具有良好的适用性。      

纤维缠绕复合材料夹芯圆柱体准静态压缩吸能机制

提出并设计了一种新型纤维缠绕复合材料夹芯圆柱体吸能结构单元。为探讨其在准静态压缩载荷作用下初始损伤的产生、扩展及演变规律,基于ABAQUS建立该单元数值分析模型,并开展了准静态压缩试验。数值模拟与试验现象综合分析表明,准静态压缩载荷作用下单元结构的响应具有三阶段特征,包括初始线弹性压缩阶段、渐进损伤阶段和结构破坏阶段。固体浮力芯材在压缩载荷作用下产生塑性损伤变形和剪切断裂破坏,纤维缠绕复合材料表层在芯材横向膨胀效应引起的环向应力作用下发生环向纤维的拉伸断裂破坏,导致单元结构稳态吸能过程的终止。研究结果表明,该单元比吸能效率远高于传统的复合材料圆柱壳结构。     

准静态压痕力作用下复合材料层压板的损伤阻抗分析

建立了一种复合材料层压板在准静态压痕力作用下的损伤阻抗的预测方法。首先分别针对基体破坏、分层、 纤维断裂等失效模式引入相应的失效变量 , 并建立不同失效模式下的刚度折减方法 , 然后采用基于应变描述的 Hashin和 Yeh失效准则并结合有限元方法 , 对复合材料层压板在准静态压痕力作用下的破坏过程进行渐进损伤分析 , 在此基础上进一步预测了层压板的损伤阻抗。采用商用有限元软件 ABAQUS/ Standard 的 UMAT用户子程序实现数值模拟。计算结果表明 , 分层起始与扩展是导致载荷2位移曲线发生第 1 次卸载的主要原因 , 当接触力达到其最大值时出现较明显的纤维断裂。分层起始载荷和最大接触力的预测结果与实验数据吻合良好。     

复合材料开孔层板压缩渐进损伤试验

为研究碳纤维增强树脂基复合材料开孔层板在压缩加载过程中的损伤起始、演化方式和损伤特点,采用微距拍摄、逐级加载超声C扫描、X光扫描和扫描电子显微镜观测4种观测手段对国产CCF300/5228A[45/0/-45/90]4s、[452/02/-452/902]2s、[454/04/-454/904]s3种铺层方式的开孔层板进行了压缩试验研究。对压缩载荷作用下开孔层板的损伤起始和损伤演化进行了观察和对比。对试验中观测到的纤维微屈曲、纤维挤出、孔边开裂和分层扩展等现象之间的关系进行了分析和说明。试验结果表明:压缩载荷下45°和90°铺层相邻位置为层板易分层位置,含45°和90°铺层相邻位置的开孔层板渐进损伤过程较为明显:开孔层板在压缩载荷下较早出现损伤,损伤的起始和演化缓解了孔边应力集中,促使压缩应变能在孔边逐步释放,推迟开孔层板压缩破坏的发生,提高层板压缩承载能力。研究结果可为材料结构损伤容限设计提供依据。     

准静态压痕力作用下复合材料层合板的凹坑深度预测方法

建立了一种在准静态压痕力作用下复合材料层合板凹坑深度的预测方法。首先采用基于应变描述的Hashin 和 Yeh 失效准则并结合有限元法, 对复合材料层合板在准静态压痕力作用下的失效过程进行渐进损伤分析, 获取一系列的材料性能退化信息。其次采用Sun的方法对局部损伤区材料的弹性参数进行等效处理。最后结合Turner的接触理论预测了凹坑深度-接触力曲线。计算结果表明, 基体开裂与分层是导致层合板开始产生凹坑的主要原因, 纤维断裂是导致凹坑深度急剧增加的主要原因。分层起始载荷、 最大接触力及各自相应的凹坑深度的预测结果与试验值具有较好的一致性。      

缝合复合材料层板低速冲击损伤数值模拟

建立了缝合复合材料层板在低速冲击载荷下的渐进损伤分析模型。模型中采用空间杆单元模拟缝线的作用;采用三维实体单元模拟缝合层板,通过基于应变描述的Hashin准则,结合相应的材料性能退化方案模拟层板的损伤和演化;采用界面单元模拟层间界面,结合传统的应力失效判据和断裂力学中的应变能释放率准则判断分层的起始和扩展规律。通过对碳800环氧树脂复合材料（T800/5228）层板的数值仿真结果和试验结果相比较,验证了模型的正确性,同时讨论了不同冲击能量下缝合层板的损伤规律。研究结果表明：缝线能够有效地抑制层板的分层损伤扩展;相同冲击能量下缝合与未缝合层板的基体损伤和纤维损伤在厚度分布上相似,缝合层板的损伤都要小于未缝合层板。     

基于Puck理论的复合材料层合板横向剪切失效分析

针对复合材料层合板三维失效分析问题,建立了一种基于Puck失效准则的分析模型。针对Puck失效理论中的基体失效,分别采用遍历法和分区黄金分割法（PGSS）的一维搜索算法预测了不同应力状态下基体失效的断裂面角度,并对比分析了两种算法的计算精度和计算效率。研究表明,PGSS具有较高的搜索精度和搜索效率。在ABAQUS有限元分析平台下,编写了基于Puck失效准则的VUMAT显式用户自定义材料子程序,对复合材料层合板横向（G₂₃）剪切性能进行了数值预测和渐进失效分析,并与试验载荷-位移曲线、DIC测得的应变场及破坏模式进行了对比。分析结果表明:当前的分析模型能较好地预测复合材料层合板G₂₃剪切试验的力学响应和破坏模式。      

弯剪复合载荷作用下复合材料层合板屈曲的强度校核方法

基于复合材料各向异性板的大挠度方程,采用Ritz法和最小势能原理推导出了正交各向异性复合材料层合板在面内弯曲载荷作用下临界屈曲弯矩的解析解;给出了面内弯剪复合载荷作用下复合材料层合板屈曲的强度校核方法,并将本文方法所得结果与用有限元法（FEM）所得结果进行了比较。结果表明,本文方法与有限元方法相吻合,并且形式简洁,便于工程应用。     

Fatigue behaviour of a box-welded joint under biaxial cyclic loading: effects of biaxial load range ratio and cyclic compressive loads in the lateral direction

ABSTRACT The biaxial fatigue of a steel plate (JIS SM400B) having a box‐welded (wrap‐around) joint was experimentally studied. Special concerns were focused on the effects of the biaxial load range ratio and compressive cyclic loading in the lateral direction. The direction of fatigue crack propagation under biaxial cyclic tensile loading, which has a phase difference of π, changed according to the biaxial load range ratio, R_xy = ΔP_x/ΔP_y. When R_xy was less than 0.56, fatigue cracks propagated along the toe of the weld in the x‐direction because the principal tensile stress range Δσ_y at that location exceeded the orthogonal value Δσ_x at the box‐weld toe. The fatigue lives in biaxial tests related well to the data from uniaxial tests when invoking the Δσ₅ criterion. However, the location and direction of Δσ₅ should be chosen according to the R_xy value and the failure crack direction. An increase in Δσ₅, as induced by the Poisson's ratio effect from either the out‐of‐phase tensile loading or the in‐phase compressive loading in the y‐direction, leads to an increase in fatigue damage (decrease in fatigue resistance or specifically a faster crack propagation rate), and this effect can be successfully estimated from uniaxial fatigue test data.     

复杂载荷下钢带缠绕增强复合管力学特性

为研究海洋油气输送用钢带缠绕增强复合管在复杂载荷下的力学响应特性,考虑非线性接触,建立钢带缠绕增强复合管数值计算模型,研究由内外压、弯曲及拉伸载荷组合作用下钢带缠绕增强复合管的变形及承载性能.结果表明,压差(外压大于内压,≤2MPa)越大钢带缠绕增强复合管的柔性越高.与纯弯曲相比,拉伸载荷和压差的附加联合作用使钢带缠绕...     

Deformation behavior of woven glass/epoxy composite substrate under thermo-mechanical loading

The deformation behaviors of woven glass/epoxy composite substrate under four thermo-mechanical loading paths, i.e. rectangular and triangular paths in clockwise and anticlockwise directions within a temperature range of 25–250 °C were investigated. Temperature scanning tests were conducted to identify the viscoelastic property of the material. The glass transition temperature of the composite substrate was 138 °C, above which significant reduction of storage modulus was observed. The deformation behavior of the composite substrate was temperature and history dependent, and change of deformation rate resulted from state transition was noticeable. The residual deformation of specimen following the anticlockwise rectangular loading path was the largest in contrast with the lowest in clockwise rectangular path. The residual deformations in two triangular paths were close after each cycle.     

A comparison of total fatigue life models for composite laminates

A total fatigue life model proposed previously by the same authors for laminated composite structures subjected to mode‐I fracture loading is evaluated by two newer models. The new models differ from the original model by normalization factor and approximation of stable delamination growth rate equation. All three models include the delamination growth in subcritical (delamination initiation), linear (stable growth) and final (unstable growth) fracture domains. All three models were evaluated by comparing the total life predictions for two different block loadings. One is a normal operation of a rotor craft‐type structure and the other is an aggressive loading. Predicted results of the three models were compared with each other and with the experimental data. The material considered was woven‐roving E‐glass fibre and vinyl ester matrix and the laminate was made by vacuum assisted resin transfer molding.     

双轴载荷下复合材料十字型试样几何形状对中心测试区系数的影响

基于双轴拉伸载荷下复合材料十字型试样的设计特点,对比分析了不同几何形状的十字型试样在不同厚度比和载荷比条件下中心测试区应力集中系数和承力系数的变化规律,并开展了不同载荷比的双轴拉伸实验进行验证。研究表明:十字型试样中心测试区系数与载荷大小无关,与试样几何形状、厚度比及载荷比有关;等宽加载臂宽度越小、厚度比越大,应力集中系数越小,载荷比不同,应力集中系数也不同;一般而言,中心测试区承力系数随厚度比增加而增大,x向承力系数βx随载荷比增加呈非线性增大,y向承力系数βy随载荷比增加呈线性减小;在双轴拉伸载荷条件下,形状D十字型试样在载荷比f=4/1时中心测试区y向应力分量为负值,表现为压应力状态。