材料基础知识

应力：应力（工程应力或名义应力）σ=P/A。

式中，P为载荷；A。

为试样的原始截面积应变：应变（工程应变或名义应变）ε=（L-L。

）/L。

；L。

为试样的原始标距长度一般是（20mm 25mm 50mm）引伸计；L为试样变形后的长度拉伸的应力应变曲线斜率就是拉伸模量。

拉伸模量大，拉伸性能好拉伸模量：（Tensile Modulus）是指材料在拉伸时的弹性，其计算公式如下：拉伸模量（㎏/c㎡)=△f/△h(㎏/c㎡)其中，△f表示单位面积两点之间的力变化，△h表示以上两点之间的距离变化。

更具体地说，△h=（L-L0）/L0，其中L0表示拉伸长前的长度，L表示拉伸长后的长度。

霍普金森压杆应变率：g.mm-3强度：模量：模量＝拉伸强度/应变应力应变曲线中最高的拉伸强度通常是最大的应力力学性能表征量:拉压弯剪ESEM 环境扫描电镜：environment scanning electron microscopeInfiltration 渗透渗透物XRD：X-ray diffraction ，X射线衍射，通过对材料进行X射线衍射，分析其衍射图谱，分析材料的成分等闪点（Flash point）是指可燃性液体挥发出的蒸汽在与空气混合形成可燃性混合物并达到一定浓度之后，遇火源时能够闪烁起火的最低温度。

在这温度下燃烧无法持续，但如果温度继续攀升则可能引发大火。

和着火点（Fire Point）不同的是，着火点是指可燃性混合物能够持续燃烧的最低温度，高于闪点。

闪点的高低也是染液是否安全的重要指标。

剥离强度（peel strength）：粘贴在一起的材料，从接触面进行单位宽度剥离时所需要的最大力。

剥离时角度有90度或180度，单位为：牛顿/米（N/m）。

它反应材料的粘结强度。

如安全膜与玻璃。

MWK 多轴向径向编织复合材料Multi-axial warp knittedThreshold strain level阈值应变水平Longitudinal and transverse 横向和纵向的Through-thickness reinforcement of polymer laminatesChanges in the interior structure and mechanical response of composite materials may occur under such conditions内部结构的变化和复合材料的力学响应可能发生在这种情况下tensile strength and modulus 拉伸强度和模量specific strength 比强度；强度系数specific modulus比模量塑性是一种在某种给定载荷下,材料产生永久变形的材料特性,对大多的工程材料来说,当其应力低于比例极限时,应力一应变关系是线性的。

英文专业名：Plasticity. Ductility, Briquettability.塑性材料的数据一般以拉伸的应力—应变曲线形式给出。

材料数据可能是工程应力（p/A0）与工程应变（dl/l0），也可能是真实应力（P/A）与真实应变（Ln (l/l0) ）。

大应变的塑性分析一般采用真实的应力，应变数据而小应变分析一般采用工程的应力、应变数据。

在材料科学及冶金学上，韧性是指当承受应力时对折断的抵抗，其定义为材料在破裂前所能吸收的能量与体积的比值。

flexure modulus 弯曲模量load/deflection curves负载/挠度曲线braiding angle,编织角initial stage,初始阶段,stress displacement curve应力位移曲线The damage and fracture morphology of the composite samples after bending testswere observed by a FEI Quanta250 Field Emission Scanning Electron Microscope (FESEM).All the curves linearly increase at the initial stage, but with different slopes。

At the room temperature (19 C), the load immediately drops after it has reached the maximal point, and no clear yield phenomenon can be observed在室温(19 C),加载后立即地已达到最大点,没有明确的屈服现象可以观察到。

brittle fracture feature脆性断裂特征platform['plætfɔːm]n. 台，平台E为弯曲模量，l为试样跨距30mm，Δp为力的改变量，b为试样的宽度，h 为试样的厚度，Δf为形变的改变量。

σ为弯曲强度，p为最大力。

fibers fracture smooth cross-sections纤维断裂是光滑截面interface between fibers and matrix remains high strength bonding纤维和基体之间的接口仍高强度粘合plastic deformation[力] 塑性变形，塑性应变l裂纹扩展的英文名：crack propagation用平纹组织织成的织物叫平纹织物。

就是经纱和纬纱每隔一根纱就交织一次（即纱是1上1下的）。

这种布的特点是交织点多，质地坚牢、挺刮、表面平整，较为轻薄耐磨性好，透气性好。

平纹布的基本特征是采用平纹组织，纱线在织物中的交织点多，使织物挺括坚牢，比同规格的其它组织织物耐磨性好，强度高，布面匀整且正反面相同。

无纬布高性能纤维“UD”无纬布，是采用超高强•高模聚乙烯纤维为基材，经先进高科技设备均匀铺丝，用高强弹性体树脂浸渍涂胶和薄膜粘合，再经0°/90°；双正交复合层压而成。

该产品具有手感柔软、密度小、耐磨蚀、抗冲击、抗切割韧性强等优异性能，产品广泛应用于软质防弹衣、轻质防弹头盔、轻质防弹装甲板材，防刺、防切割服装衬片和特殊公共防暴设施，是当今世界强度最高、比重最轻的防弹材料。

网胎见pptplain cloth平纹布non-woven cloth 无纬布Tensile stress (rt)–strain (et) plots for the nonwoven compositesin the longitudinal direction at room temperature (RT) and 77 K areshown in Fig. 5a. These represent typical examples of the stress–strain curves. Some nonlinearity can be seen in tensile stress–应力应变曲线非线性的原因strain responses. This may be the result of progressive failuredue to various interacting micro-failure modes, such as matrix 基体破坏和纤维剥离cracking and fiber debonding [1]. The nonlinear behavior at roomtemperature can also be attributed to the material nonlinearityof polymeric materials, and the near-linear behavior at 77 K canbe related to polymer hardening. In addition, the nonwoven compositesfail in a brittle manner. Fig. 5b exhibits initial parts of tensilestress–strain curves. The lines in the figure show the linearfitting curves, and the initial slope of the stress–strain curve wastaken as the Young’s modulus. Fig. 6宏观断裂图shows typical specimens afterthe tension tests at room temperature and 77 K. Failure occurs inthe gage section of the specimens.Table 1 summarizes the Young’smoduli in tension Et, ultimate tensile strengths rtB and strains-to failure 对表格模量强度的描述etB at room temperature and 77 K. In the table, the overbarrepresents the average value. The tensile Young’s modulus andultimate tensile strength increase as temperature decreases fromroom temperature to 77 K. This can be explained by the temperaturedependence of the constituent material properties [10]. Also,the strain-to-failure应变造成的损害decreases as temperature varies from room temperature to 77 K since cryogenic temperatures cause polymersystems to become less ductile. Fig. 7 shows the SEM images ofthe fracture surfaces for the tension test specimens at room temperatureand 77 K. Fiber/matrix interface debonding is found onthe fracture surfaces. Also, the fibers aligned perpendicular to the垂直于断裂表面的纤维fracture surface are pulled out from the matrix after the interfacedebonding. These features are a result of a poor interface bondingbetween the fiber and the matrix. Obvious cleavage planes areshown in the matrix region, indicating brittle fracture. This isconsistent with the brittle behavior observed during testing. Itshould be noted that the failure mechanism is independent oftemperature.断裂机理不受温度的影响Typical flexural load (P)–deflection (d) curves at room temperatureand 77 K are illustrated in Fig. 9. The flexural behavior at roomtemperature is slightly nonlinear while the behavior at 77 K is linear.The composite specimen loses its load carrying capacity instantlyafter the maximum load. Fig. 10 shows representativephotographs of the specimens after the flexure tests at room temperatureand 77 K. The specimen failure is located within the span.Table 3 presents the flexural moduli Ef and flexural strengths rfB atroom temperature and 77 K. At both temperatures, the flexuralstrength is higher than the ultimate tensile strength. The differencebetween the flexural and tensile strengths may be due to the presenceof a stress gradient in the flexure test [12]. The flexural modulusand strength at 77 K are higher than those at roomtemperature. The SEM images of Fig. 11 show the fracture surfaceson the tensile side of the flexure test specimens at room temperatureand 77 K. Fiber/matrix interface debonding and matrix cleavagefracture are observed. Based on the classical beam theory, theshear stress varies parabolically through the specimen thicknessand the maximum shear stress occurs at the midplane. Also, thebeam theory predicts that the longitudinal normal stress distributionvaries linearly through the thickness and is a maximum at thebottom surface. Thus, the effect of the shear stress on the flexuralfailure may be small. As a result, the fracture surfaces for the flexurespecimens exhibit similar characteristics to those for the tensiontest specimens.结论The interface debonding between the fiber and the matrix isseen on the tensile fracture surfaces. The matrix material alsoexhibits a typical fractographic feature of brittle fracturebehavior. In addition, fractographic examination shows littledifference in composite failure mechanism between roomtemperature and 77 K.材料的破坏分塑性破坏和脆性破坏两种。