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《玻璃钢/复合材料》2021,(2)
以重组竹为代表的竹纤维复合材料是具准脆性断裂特征的生物基纤维复合材料,强度值存在尺寸效应问题,影响其构件的设计理论。为研究重组竹的强度尤其是纵向拉伸强度的尺寸效应现象,进行了三点弯曲试验与直接拉伸试验测试材料的尺寸效应行为,并应用基于断裂理论的拉伸强度模型分析材料缺陷尺寸及尺寸效应的计算方法。试验结果表明,重组竹的拉伸强度存在明显的尺寸效应现象,而基于断裂理论的拉伸强度模型可计算不受尺寸效应限制的理论塑性拉伸强度,且该塑性拉伸强度考虑了材料表面的缺陷影响。因此,尺寸效应对重组竹纵向拉伸强度的影响可采用理论塑性拉伸强度与表面缺陷尺寸确定。 相似文献
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玻纤/环氧层合板三点弯曲强度分布及其预测 总被引:1,自引:0,他引:1
本文应用概率和断裂力学,从体积微裂纹的研究出发探讨了复合材料的强度分布。进行了加载方向垂直和平行于纤维所在面的三点弯曲破坏试验。拟合检验了玻纤/环氧层合反在三点弯曲时的强度遵循σu=0的Weibull分布,并估计了分布参数。给出了试样的平均强度、体积和强度分布参数间的关系。预测了不同体积试样的强度。 相似文献
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纤维缠绕CFRP圆管强度特性分析及试验研究 总被引:2,自引:2,他引:0
首先,本文采用各向异性弹性力学的方法,结合复合材料层合理论,研究了纤维缠绕层合圆管的应力分析和变形分析方法;其次,分析了由碳纤维复合材料(CFRP)构成的圆管的强度;而后,对纤维缠绕成型的两种尺寸的CFRP圆管进行压缩和拉伸实验,着重研究了CFRP圆管在这两种受力状态下直至破坏的应力-应变关系、极限强度以及材料宏观破坏模式. 相似文献
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本文提出了一种简单有效的预氧化处理方法,用来强化反应烧结碳化硅(RBSC),研究了800~1 300 ℃预氧化处理对其微观结构和力学性能的影响,探究了含不同尺寸压痕裂纹的材料在氧化前后残余弯曲强度的变化规律。结果表明,随着氧化温度的升高,RBSC的室温强度和Weibull模数均存在先下降后上升,然后再下降的趋势,主要原因是不同温度氧化后的RBSC表面形貌不同。在1 200 ℃下预氧化2 h,RBSC的弯曲强度和Weibull模数都明显变大,强度提升了19.9%,Weibull模数由7.3提升到11.8。然而,800 ℃低温氧化不完全和1 300 ℃高温氧化反应过于强烈均会导致弯曲强度和Weibull模数下降。在最优氧化条件(1 200 ℃氧化2 h)下,含压痕裂纹(载荷20 N)的RBSC试样的残余弯曲强度在氧化后由201.1 MPa提高到324.2 MPa,强化机理是高温氧化生成的SiO2能够消除材料表面缺陷和微裂纹。 相似文献
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采用经典复合材料混合率公式[σ]=σfVf+σm(1-Vf)预测国产碳纤维复合材料(CFRP)筋拉伸强度与实测值存在较大误差。本文通过大量实验分析,分别研究复合材料界面粘结性不同,碳纤维、树脂力学性能、体积含量不同,以及复合材料宏观尺寸、形貌差异等对国产CFRP筋拉伸强度及其预测值的离散性影响规律,并对影响因素进行评价。综合试验数据,提出CFRP筋轴向拉伸强度混合率公式修正因子。 相似文献
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考虑残余应力对压痕弯曲梁应力场强度的贡献后,对相应的K_(IC)表达式进行了修正。研究表明:在合适的压痕压制荷载范围内,弯曲梁强度σ_r与压痕裂纹深度的倒数平方根(1/a)~(1/2)之间存在线性关系;压痕处的残余应力效应可以用σ_(?)-(1/a)~(1/2)直线关系式中的强度修正项加以描述。高温下强度修正项的值随温度的升高而减小,说明残余应力在高温作用下得到了部分消除;退火处理也导致了强度修正项的减小。采用强度修正项后的K_(IC)计算公式,压痕弯曲梁法可望应用于各种温度下的K_(IC)测试;由σ_(?)(1/a)~(1/2)直线斜率求得的K_(IC)值不受残余应力影响。 相似文献
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含缺陷陶瓷材料的强度 总被引:3,自引:0,他引:3
含缺陷材料强度不仅与缺陷的形状,尺寸有关,而且还与材料脆性相关的破坏发生区的大小有关。由此推导了含各种缺陷材料的强度方程,计算了不影响材料强度的临界缺陷尺寸。最后,用含有各种人工缺陷的Si3N4试样进行了验证实验。 相似文献
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复合材料圆管弯曲强度研究 总被引:1,自引:0,他引:1
对两组不同支距(100,200,300,400,500mm),在管芯加与不加塞子情况下的纤维增强复合材料圆管进行了弯曲试验。结果显示加与不加塞子,对圆管的弯曲强度的试验结果影响很大。对于所测试的玻璃纤维增强复合材料圆管,管芯不加塞子情况下的纤维增强复合材料圆管的弯曲强度约为加塞时的42%~60%,试验结果离散性较加塞时高出2%~4%。为探索一种合理的复合材料圆管弯曲性能的评价方法,本文对此现象进行了分析,建立了复合材料圆管弯曲强度模型,并采用修正的Hill平面应力准则给出了加与不加塞子情况下两者弯曲强度之间的关系。理论计算结果与测试值符合得很好,表明可以采用管芯加塞弯曲实验方法,再利用本文所建立的关系获得复合材料圆管较真实的弯曲强度。 相似文献
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Mineo Mizuno 《Journal of the American Ceramic Society》1991,74(12):3017-3022
The microstructure of mullite ceramics hot-pressed and sintered at different temperatures was studied using transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) with EDS, and electron probe microanalysis (EPMA). The specimens, consisting of stoichiometric mullite grains without glassy phase, are obtained by hot-pressing stoichiometric mullite powder at 1575°C for 1 h. Silica-rich glassy phases are observed using TEM at three-grain junctions of mullite grains in specimens heated at and above 1600°C. However, high-resolution transmission electron micrographs show no glassy phase at two-grain boundaries in all specimens. SEM with EDS analyses show that the average value of Al2 O3 contents of mullite grains increases slightly with increasing temperature. These results are consistent with a published Al2 O3 –SiO2 phase diagram. The flexural strength of mullite specimens at room temperature depends on their microstructure, such as the grain size and grain size distribution of mullite grains. The strength is high at room temperature and up to 1200°C, and it decreases at and above 1350°C, irrespective of the presence of the glassy phase. 相似文献
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Experimental Method for a Dynamic Biaxial Flexural Strength Test of Thin Ceramic Substrates 总被引:2,自引:0,他引:2
A dynamic piston-on-three-ball experimental technique has been developed for a biaxial flexural strength test of thin ceramic substrates at high loading rates. Analytical modeling of the technique guided the experimental design and was used to judge the validity of experimental results. Thin ceramic substrates made of 1-mol%-Al2 O3 -doped 8-mol%-yttria-stabilized zirconia (8YSZ) were tested using this experimental technique, as well as its standard counterpart—the quasi-static piston-on-three-ball technique. Results show that the mean biaxial flexural strength increased from ∼322 to ∼465 MPa as the average loading rate was increased from quasi-static to dynamic (830 GPa/s) level. 相似文献
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高抗冲高刚性EPDM改性聚丙烯的研究 总被引:2,自引:0,他引:2
加入超细改性无机刚性粒子提高三元乙丙橡胶(EPDM)的硬度,再与聚丙烯(PP)进行共混。研究了超细改性无机刚性粒子用量对EPDM硬度及流动性的影响,比较了PP与不同硬度EPDM的共混物在力学性能上的差异。结果表明:随着EPDM硬度的增加,共混物不仅韧性提高,弯曲模量也大幅度上升。选择合适的硬度,可制得高抗冲高刚性的EPDM改性PP共混材料。 相似文献
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在玻璃陶瓷基板材料中加入PS有机球能有效地降低基板的介电常数,但同时影响基板的抗折强度。通过建立空心球力学模型,得到基板材料的有效体积模量和有效杨氏模量的表达式,从而推导出表达闭合孔孔隙率与抗折强度之间关系的公式。该公式与实验结果符合较好。 相似文献
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The effect of surface-conditioning of fiber-posts on the flexural strength of the post and on the adhesion between the root dentin and cement and between the fiber-post and the composite core were assessed. The fiber-posts were subjected to cleaning with alcohol (AL), treatment with AL + silane (SIL), sandblasting with Al2O3 particles + SIL, H2O2 etching + SIL, hydrofluoric acid etching + SIL, and H3PO4 etching + SIL. For comparison, another group of specimens was left unconditioned (control group). The conditioned fiber-posts were cemented to bovine roots, and standardized cylindrical resin cores were fabricated. The specimens were subjected to 106 mechanical pulses and then sectioned perpendicular to the long axis of the root. Push-out tests were conducted on the sliced root sections, and microtensile testing was applied to the trimmed sliced core sections. The posts were also subjected to three-point bending tests. The surface-conditioning did not have any significant effect on the push-out strength. However, silanization increased the microtensile strength at the resin core. Sandblasting significantly decreased the flexural strength as compared to other surface treatments. Our study indicates that post surface-conditioning did not improve the post retention in the root canal, although silanization enhanced the adhesion to the core resin. Sandblasting with 125-µm alumina particles should be avoided. 相似文献
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