影响塑料性能测试结果的因素分析

以低密度聚乙烯(LDPE)薄膜和抗冲共聚聚丙烯为例,讨论了制样工艺及测试中的各种因素对塑料性能测试的影响.结果表明,制样工艺对材料的性能影响很大;在制样过程中需考虑各工艺参数间的关系,减小和避免试样内部缺陷的产生,从而减小或避免制样工艺对塑料性能测试结果的影响;在冲击强度测试中,制备样品缺口的刀具速度对测试结果产生影响;测试熔体质量流动速率时,口模直径、温度对测试结果产生影响,在测试中需注意这些影响因素,可减小和避免其对结果的影响.     

关于抗冲击聚苯乙烯(PS-1)悬冲强度测试结果再现性的探讨

抗冲击聚苯乙烯(PS-1)悬臂梁缺口冲击强度测试是与制样、环境状态调节、铣缺口、测试环节等多个要素相关的条件实验,这些实验条件直接影响了冲击强度的再现性.由于仪器等条件限制,目前国内各生产厂家执行的制样及检测标准不完全一致,导致分析结果可比性差.本文注重讨论如何提高 PS-1悬臂梁冲击强度测试结果的再现性问题,使不同生产企业的抗冲击聚苯乙烯(PS-1)的悬臂梁冲击强度结果有较好的可比性.     

不同制样方法对塑料悬臂梁缺口冲击强度的影响

在测试聚乙烯产品的悬臂梁缺口冲击强度时,发现采用压塑法和注塑法制得的样条测试结果有较大区别,本文就两种不同制样方法引起聚乙烯产品冲击强度变化的原因进行分析,认为制样对结晶尺寸和分子的取向性的影响是造成强度变化的原因。     

制样方式及注塑工艺对聚酰胺6抗冲击性能的影响

通过改变注塑压力、注塑速度、模具温度、注塑温度等注塑成型工艺参数,研究了两种制样方式对改性聚酰胺(PA)6抗冲击性能的影响.结果表明:相同注塑成型工艺条件下,自带缺口试样的冲击强度都高于自制缺口的试样;注塑压力和注塑速度对自带缺口试样的冲击强度影响较大,但对自制缺口试样的冲击强度影响不大;模具温度和注塑温度对两种制样方...     

丙烯腈-丁二烯-苯乙烯共聚物缺口试样悬臂梁冲击强度研究

通过改变不同的测试条件,对丙烯腈-丁二烯-苯乙烯共聚物(ABS树脂)缺口试样悬臂梁冲击强度测试结果的影响因素进行了对比和分析,发现试样在状态调节与铣缺口操作先后顺序条件下的状态调节时间、铣缺口的工艺和不同摆锤能量对ABS树脂缺口试样悬臂梁冲击强度测试值影响不大,试样缺口中心相对台钳平面距离是影响ABS树脂缺口试样悬臂梁冲击强度测试值的主要因素。     

聚丙烯材料简支梁缺口冲击性能的时温效应研究

将聚丙烯(PP)树脂在一定注塑工艺条件下制备成用于简支梁冲击测试的样条,分别为ISO注塑A型缺口冲击样条和无缺口样条(然后通过铣缺口机机械加工成A型缺口冲击样条),通过摆锤冲击试验仪进行简支梁缺口冲击强度测试,研究共聚型PP材料注塑缺口和铣缺口冲击性能的时温效应。结果表明,共聚型PP材料铣缺口在标准环境下调节,简支梁缺口冲击强度基本无变化,机械加工内应力对其影响较小;注塑缺口在标准环境下调节,简支梁缺口冲击强度随着调节时间的延长先快速降低,后缓慢衰减;注塑缺口的冲击强度明显大于铣缺口的冲击强度;缺口冲击强度与温度成指数型增长。     

不同条件对聚碳酸酯缺口冲击强度测试结果的影响

以纯聚碳酸酯(PC)、阻燃PC和阻燃增韧PC试样为研究对象,研究了ISO 7391–2,ASTM D256和ISO180三种标准测试的悬臂梁缺口冲击强度差异,同时探讨了缺口制作方式和退火处理(135℃,2h)对缺口冲击强度测试结果的影响。结果表明,不同PC试样采用ASTM D256标准测试的缺口冲击强度较ISO 7391–2稍高,而采用ISO 180标准测试的缺口冲击强度最低。偏光应力仪和扫描电子显微镜测试结果表明,由于ISO 180标准规定的试样厚度相对较大,试样产生了过大的残余应力,加之阻燃PC中阻燃剂与PC的相容性较差,进而导致采用ISO 180标准测试的阻燃PC缺口冲击强度测试数据极低。实际应用中尽量选用断裂行程短、试样厚度大的ISO 180标准对改性PC试样的缺口冲击强度进行测试,其更能体现材料的缺陷和实际韧性。采用机铣缺口测试的缺口冲击强度稍高,而采用模塑缺口测试的缺口冲击强度离散系数小,数据稳定性更好。退火处理虽可消除试样的内部应力,但会导致试样边缘位置应力集中更加明显,退火处理后各试样的缺口冲击强度测试数据均大幅度降低。     

试样缺口对悬臂梁缺口冲击强度测试结果的影响研究

选择聚碳酸酯（PC）、均聚聚丙烯（PP）、聚氯乙烯（PVC）和聚丙烯腈-丁二烯-苯乙烯树脂（ABS）四种原材料作为研究对象,对比研究试样缺口差异对悬臂梁缺口冲击强度测试结果的影响。结果表明,PC材料的注塑试样和机铣试样的冲击强度均值相同,但是前者的波动明显高于后者;而对于均聚PP,注塑试样的冲击强度明显高于机铣试样;另外相比于PVC,缺口加工方式、缺口加工速度以及缺口剩余宽度对ABS材料的冲击强度结果影响不大。     

样品制备工艺对石材干挂胶性能测试结果的影响

探讨了石材干挂胶性能测试中样品制备工艺对钢/钢拉剪强度和冲击强度测试结果的影响。结果表明,制备钢/钢拉剪样品时用垫丝控制胶层厚度的方法,控厚更精确,测试结果重复性好;相比于硅胶模具,钢模具制2备的试样冲击强度要高出0.5~0.8 k J/m,样品制备中不同的表面找平方法对冲击强度的影响相对较小。     

影响塑料冲击试验结果的因素

阐述了试样尺寸,温度、湿度、缺口以及缺口加工方式等因素对塑料冲击强度测试结果的影响。     

Evaluation of a structural epoxy adhesive for timber-glass bonds under shear loading and different environmental conditions

This article presents a study of timber-glass adhesive joints. It examines the shear specimen and shear tools preparation process and the evaluation of the results backed up with an overview of existing similar studies. The chosen adhesive was a cold-curing two-component structural bonding epoxy resin (Mapei Adesilex PG1). The shear tests were performed under different temperatures and the timber samples had different moisture contents. A simple shear test tool was designed and was clamped into a universal testing machine for the shear test. The force and crosshead displacement values from the universal testing machine were used for evaluating the results. The environmental conditions of 20 °C and 5% timber moisture content resulted in the highest average shear strength obtained from the shear tests of the analysed joints (9.89 MPa), whereas the environmental conditions of 50 °C and 20% timber moisture content resulted in the lowest average shear strength (3.42 MPa). It was found that the joint strength is dependent on the environmental temperature and timber moisture content. Moreover, the shear specimen load-displacement behaviour at the environmental temperature of 50 °C was linear and nonlinear – depending on the timber moisture content. The most frequent failure type was timber failure. Additionally, a nonlinear contact finite element analysis was performed to demonstrate the additional shear specimen rotation due to the clearance between the shear specimen and shear tools. This impact was evaluated regarding the stress distribution in the bond line. The evaluated epoxy resin adhesive was proved to be suitable for timber-glass bonds.     

Specimen design,manufacturing and testing procedures for flat carbon fiber reinforced plastic laminates under biaxial loading

The optimization of a specimen design allowing the investigation of the biaxial strength of composite laminates over the full range of failure strain was the primary objective of this work. Multiaxial strength criteria are often found unreliable mainly as a result of the inherent complexity of biaxial tests and, in many cases, as a result of inefficient specimen designs. As a result of a development program combining numerical simulations and experimental measurements, a flat cruciform-shaped specimen has been developed for carbon fiber reinforced plastic (CFRP) laminates. The design fulfills the basic criteria for such a specimen, namely allowing for a uniform biaxial stress/strain state to exist in the gauge area and for testing the virgin material up to failure in both the tension-tension and tension-compression quadrants of the strain/stress space. The fabrication of the specimen is described and a three-step testing procedure for generating biaxial strength data is proposed. Typical results obtained from specimens of the proposed configuration tested in accordance with this procedure are presented. Results compare well with those obtained from tubular specimens, thus confirming the effectiveness of the proposed design. Experimental data obtained for the AS4/3501-6 carbon/epoxy composite system are finally compared against strength predictions of recognized failure theories.     

Valid KIC Determination via In-Test Subcritical Precracking of Chevron-Notched Bend Bars

The initiation of the crack in a chevronnotched bend bar was studied. Ideal testing conditions depend strongly on specimen preparation and material; valid K_IC values do not always result. An in-test precracking technique was developed for ceramics at room and elevated temperatures. A yttria-partially-stabilized zirconia ceramic was tested, and the results showed that ideal testing conditions were obtained, which guaranteed valid K_IC determination.     

Mechanical Failure Characteristics of Ceramic Multilayer Capacitors

The results of both uniaxial and biaxial flexure as well as toughness testing on actual commercial ceramic capacitor samples are reported. Necessary procedural adjustments are outlined for miniaturizing the applied-moment double-cantilever-beam test to accommodate these small samples. Strength and toughness testing showed that the metal electrodes lowered the fracture toughness and that the metal-ceramic interface was a preferred fracture path for crack propagation parallel to the electrodes. However, toughness did not clearly depend on crack propagation parallel or perpendicular to the electrodes, nor with flexural strengths. Flexural strengths were 0 to 40% lower, with the electrodes perpendicular to the tensile surface vs. parallel to the tensile surface. Fractures initiated from machining (or impact) flaws, or voids of various sizes, shapes, and locations, thus explaining the poor correlation between strength and toughness. Biaxial flexure tests of dielectric specimens of various sizes indicate that such a test could be scaled down and "calibrated" for actual testing of capacitors; e.g., a decrease in strength with increasing specimen thickness to support diameter ratio is indicated.     

Test methods for bond strength of glass fiber posts to dentin: A review

ABSTRACT

In this paper, a review of the test methods for bond strength of glass fiber posts to dentin is presented. The main variables that influence the bond strength tests are related to substrate, to specimen properties, specimen preparation, and test methodology. The impact of these variables on the test outcome is analyzed. The search was performed on studies published between 2007 and 2015. Most of the tests carried out, in the literature, were the push-out (75%), pull-out (13%), and microtensile (11.9%) tests, showing an inversion compared to the results found in studies published between 2005 and 2010, when push-out test was used in a proportion of 2% and microtensile test in a proportion of 67%. The push-out test emerged as a practical tool for evaluating the interfacial shear strength between fiber post and root canal walls.     

G／Epoxy复合材料胶接强度研究

使用G／Epoxy作为底材研究了垫板、结构胶黏剂厚度和底材表面处理对拉伸剪切强度的影响。使用光学显微镜观察了断口形貌。结果表明加垫板能减小试验过程中由于加载偏心引起剥离应力,测试结果较大;结构胶黏剂的厚度和底材表面处理对拉伸剪切强度影响十分明显,随着厚度的增大而减小,经打磨表面裸露出纤维的试样拉伸剪切强度很低。结构胶黏剂厚度较小时以内聚破坏为主,随着厚度的增加破坏模式转变为粘接破坏。     

Testing of adhesion of thin films to substrates

The results of the measurement of the adhesion strength of thin films or coatings to substrates are often influenced by system parameters that may be influenced by preparation of the specimen for testing or by deposition of the film itself. In this paper, the scratch, pull, and peel tests are analyzed in terms of criteria for film/coating removal and for the effects of system parameters such as film hardness and ductility, film thickness, substrate hardness, etc.     

石灰石粉对水泥早期性能的影响

试验采用砂浆试件,分别掺入15%、30%以及50%的石灰石粉,以早期抗折、抗压强度及水化热为研究对象,并以粉煤灰作对比研究石灰石粉对水泥早期性能的影响。研究结果表明:石灰石粉掺量为15%时,试件早期抗折、抗压强度均降低非常小,并随着水灰比的增大而加剧;同时,试件早期抗折、抗压强度随石灰石粉掺量的增大而降低,与粉煤灰相比相同掺量时石灰石粉对试件早期抗折、抗压强度的降低作用较小。石灰石粉对水泥早期水化有促进作用,选择石灰石粉作为混凝土掺合料是经济可行的。     

Glare 层板试样制备对其性能的影响研究

介绍了Glare层板的试样制备对其性能的影响。Glare层板试样制备主要包括试样设计与加工、加强片粘接以及裂纹预制等工艺,不合理的试样设计、加强片粘接缺陷以及测试工作区的加工误差都会对测试产生重要影响。