塑料土工格栅力学行为研究--Ⅱ.长周期力学行为的预测

对塑料土工格栅长期蠕变行为进行了预测。预测以有限周期内的蠕变数据为依据,采用适当的数据处理方法来进行。数据处理方法有多种,现采用了一种线性外推的方法来处理数据,得到实验温度下格栅的长周期失效时间和蠕变极限强度数据;然后再根据时温等效原理,采用WLF方程将上述结果扩展到其他温度下。预测结果显示约50~120年后,格栅的蠕变极限强度下降到原来的21%~26%。     

塑料土工格栅的长期性能与质量保证

利用时温叠加原理和最小偏差原理,对同一系列多种规格的高密度聚乙烯（HDPE）单向拉伸土工格栅在不同温度下的蠕变性能进行测试,并结合数学方法在短期内预测其长期性能。该方法置信度高,可广泛应用于塑料土工格栅质量保证及工程设计中,大大减小了工程设计的误差,确保了塑料土工格栅使用的安全性。     

大连研发单双向拉伸塑料土工格栅生产线

大连塑料研究所研制开发的单、双向拉伸塑料土工格栅生产线及技术，近日通过鉴定。专家认为，该生产线设计合理，土工格栅纵向拉伸的双极多点拉伸技术为国内外首创，横向拉伸技术采用了结构合理的夹具及先进可靠的调速手段与加温方式，生产线传动平稳，温度均匀。采用本技术生产的土工格栅，具有强度高、质量轻、价格低廉、性能可靠的特点。该产品经检测，各项性能指标达到国外同类产品水平，其中2%、5%伸长率下的单位宽度拉力均超过国际同类产品水平。本刊摘编自《中国化工报》，2002-9-2大连研发单双向拉伸塑料土工格栅生产线     

侧限荷载和温度对PE-HD土工格栅蠕变特性的影响

采用能同时研究温度和侧限荷载对土工格栅蠕变特性影响的自制设备,研究了温度和侧限荷载对高密度聚乙烯(PE-HD)土工格栅蠕变特性的影响,并采用相关性分析方法进行了分析。结果表明,在低荷载水平(拉伸强度的20%)条件下,温度和侧限荷载对土工格栅的蠕变特性影响显著。土工格栅的蠕变应变随土工格栅温度的增加而显著增大。当温度为25℃时,在侧限荷载分别为0,50,100 kPa条件下,土工格栅的最终蠕变应变比15℃时分别增大67%,77%,58%;当温度为35℃时,在侧限荷载分别为0,50,100 kPa条件下,土工格栅的最终蠕变应变比25℃时分别增大34%,35%,22%。蠕变应变随土工格栅所受侧限荷载的增加而显著减小。在侧限荷载为50 kPa条件下,土工格栅在15,25,35℃时的最终蠕变应变比无侧限荷载时减小19%,14%,14%;在侧限荷载为100 kPa条件下,土工格栅在15,25,35℃时的最终蠕变应变比侧限荷载为50 kPa时减小9%,18%,26%。对土工格栅蠕变应变与时间对数曲线进行线性拟合,拟合度大于0.9。温度、侧限荷载对土工格栅蠕变应变的相关性分别为0.735,–0.643,土工格栅温度对土工格栅蠕变应变的影响程度大于侧限荷载。     

塑料土工格栅长期蠕变行为的预测

建立塑料土工格栅蠕变性能测试室,测试了格栅试样的蠕变应变随时间的变化情况。测试在一定温度、湿度条件下进行,并对各试样加载了不同的载荷。从得到的时间-应变关系图中发现,当载荷水平较低时,蠕变发展缓慢;载荷水平较高时,蠕变发展较快且应变较大,并在测试周期内发生断裂。采用时间-温度等效和时间-应力等效相结合的叠加方法,预测了格栅的长期蠕变行为。根据叠加结果得出,格栅在温度为15℃、载荷水平为20％的使用环境下,使用寿命可达100a以上。测试的格栅试样在低于20％载荷水平下使用是安全的,而当载荷水平高于40%时,很可能在短时间内发生断裂。     

塑料土工格栅的特性及其在土木工程中的应用

介绍以聚烯烃为主要原料制备塑料土工格栅的生产工艺，塑料土工格栅具有拉伸强度高，伸长率低、与土石结合效果好，耐久性强、施工简便等特点，是一种优良的土工材料，在土木工程中得到广泛应用。     

关于塑料土工格栅冲孔模具的相关研究

冲孔模具在塑料土工格栅产品生产中占据着十分重要的地位,并且冲孔模具参数也会直接影响到生产产品的拉伸强度、单位面积质量等,加强塑料土工格栅冲孔模具研究就非常有必要。本文联系塑料土工格栅的基本概述,对塑料土工格栅生产工艺、冲孔装置、模具参数等进行细致的分析,并围绕冲孔模具工作失效问题,尝试从优化模具参数、合理模具结构、选用合适钢材、加强模具维护等方面入手,提出几点有效应对策略,以供参考。     

土工格栅拉伸速率试验分析

通过对土工格栅(塑料格栅和玻纤格栅)在不同速率下进行拉伸试验,得出拉力—变形曲线及2%,5%应变和峰值拉伸强度、最大断裂力时的延伸率等数据。经过对数据分析和曲线拟合,得出格栅受拉伸速率影响的规律,并最终选定合适的室内拉伸试验速率。结果表明,塑料格栅和玻纤格栅,纵、横向的断裂拉力随着拉伸速率的增加而增大,延伸率随着拉伸速率的增加而减小。塑料格栅和玻纤格栅,纵、横向同等规格时,纵向拉伸强度总体大于横向拉伸强度。     

塑料土工格栅拉伸过程的试验研究

通过试验研究了塑料土工格栅的拉伸过程,总结了结晶聚合物土工格栅试样拉伸的一般规律,根据聚合物拉伸理论解释了试验现象,并探讨了塑料土工格栅连续稳定拉伸的条件。试验表明,塑料土工格栅试样的各成肋部分沿纵向被依次拉伸伸长是连续生产的基础;可由材料的应力-应变关系初步判定塑料土工格栅试样拉伸的连续性,这对新型塑料土工格栅材料、工艺的研发,缩短试验周期是有利的。     

塑料土工格栅的现场破坏实验

论述塑料土工格栅现场破坏实验的必要性,以青岛颐中格栅股份有限公司生产的EGR系列塑料土工格栅为对象,进行了现场破坏实验。实验测得不同型号的塑料土工格栅在不同填料中的最高损伤因子,得到了适用于工程设计的损伤因子,并发现填料的级配是影响塑料土工格栅损伤因子的主要因素之一。     

塑料土工格栅的生产开发

综述了塑料土工格栅的生产开发进展．着重介绍了塑料土工格栅原料(聚丙烯、聚乙烯)、生产工艺、性能指标、生产企业．并提出了我国加快塑料土工格栅生产开发的建议。     

塑料土工格栅的生产与应用

介绍塑料土工格栅的生产设备，原材料配方，生产工艺流程，工艺控制要点，产品性能指标和应用。     

Creep and recovery behavior of kenaf/polypropylene nonwoven composites

This article reports an exploratory study on the creep and recovery behavior of kenaf/polypropylene nonwoven composites (KPNCs), serving as a bio‐based substitution for polypropylene (PP) plastics in the automotive industry due to the environmental concern. The creep and recovery behavior of KPNC and solid virgin PP were performed by dynamic mechanical analyzer (DMA) which allowed it to be studied extensively. The linear viscoelastic limit (LVL) was found at 1 MPa. Two popular creep models, the four‐element Burgers (FEB) model and the Findley power law (FPL) model, were used to model the creep behavior in this study. The FEB model was found only appropriate for characterizing short‐term creep behavior. In contrast, the FPL model was satisfactory for predicting the long‐term creep performance. The long‐term creep behavior of KPNC in comparison to virgin PP plastic was predicted using the time‐temperature superposition (TTS) principle. The 1‐year creep strains were estimated to be 0.32% for KPNC and 1.00% for virgin PP at 40°C. A three‐day creep test was conducted to validate the effectiveness of the TTS prediction. KPNC showed a better creep resistance and higher recoverability than the virgin PP, especially in a high‐temperature environment. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40726.     

疲劳/蠕变交互作用下塑木复合材料的断裂损伤

塑木复合材料在动态载荷作用下，其断裂损伤并非纯疲劳或纯蠕变作用的结果。利用交变载荷的试验方法，研究了在疲劳／蠕变交互作用下塑木复合材料的断裂损伤行为。结果表明，在交变载荷为破坏载荷的80％和60％时，其疲劳／蠕变断裂曲线为三段式曲线，即瞬时弹性变形阶段、延迟弹性变形阶段和加速断裂阶段；在交变载荷为破坏载荷的40％时，38h内其疲劳／蠕变曲线为两段式曲线。随着最大载荷保持时间的增加，塑木复合材料进入延迟弹性变形阶段越晚，弯曲挠度增加越快，断裂寿命降低。     

Prediction of the creep behavior of reinforced plastics

The time-dependent deformation of orthotropic and transversely isotropic viscoelastic materials under biaxial constant load is given in the range of linear and reversible stress-strain behavior for isothermal processes. This allows one to calculate the deformation of plastics on the basis of isochronous stress-strain diagrams. In addition, a method is presented which allows a calculation of the creep moduli of mat-reinforced unsaturated polyesters and their dependence on glass content, temperature, and time. This calculation requires only specific creep data of matrix material and the elastic modulus of the reinforcement.     

Uniaxial compressive creep of polytetrafluoroethylene

A machine to measure the creep deformation of plastics under uniaxial compressive loads is described. The problems associated with accurate creep testing in compression, primarily the application of a uniform stress to the specimen and the measurement of the resultant strain, receive particular attention. For the specimen geometries used, the effect on the measured strain of frictional restraints at the specimen ends is negligible provided the strain measurement is made with an extensometer attached to the specimen. The effect of fabrication techniques on the deformation behavior of polytetrafluoroethylene (PTFE) has been examined. Sintering time and temperature are found to be the most significant variables in the processing of PTFE. A comparison of uniaxial tensile and compressive creep data has shown that the non-linear viscoelastic behavior of the material extends into the low strain region.     

Creep and recovery behavior of novel organic‐inorganic polymer hybrids

A novel class of organic‐inorganic polymer hybrids were developed by meltblending up to 50 (v/v) % [about 83 (w/w) %] tin‐based polyphosphate glass (Pglass) and low‐density polyethylene (LDPE) in conventional plastics processing equipment. The creep and recovery behavior of these polymer hybrids at 30°C were studied to understand the effect of the Pglass on the creep resistance of the LDPE. The results suggest that the Pglass acts as a reinforcement and an increase in the Pglass loading leads to significantly lower creep strains. This creep resistance is further enhanced by pretreating the Pglass with coupling agents prior to incorporating them into the Pglass‐LDPE hybrids. The experimental creep compliance of these materials conformed excellently with empirical power‐law equation and a modified Burger's model, suggesting that the materials are linearly viscoelastic under the test conditions.     

不同铺层角度玻璃钢长期蠕变性能的研究

随着玻璃纤维增强复合材料的广泛应用,如何正确地分析其蠕变特性已成为最为迫切的课题之一。但由于实验方法和理论研究的不成熟性,致使玻璃钢长期性能的研究发展较为缓慢。在前人研究的基础上,制备不同铺层角度的玻璃钢试样,探究蠕变柔量随服役时间的增加而改变的特性,并建立相应的双变参理论模型,用理论公式拟合实验数据,并比较不同铺层角度蠕变性能的差异性。结果表明理论模型与实验数据契合度较高。