Assessment Of The Shear Properties Of Thermoplastic .
Manufacturing Rev. 7, 10 (2020) A.G. Stamopoulos et al., Published by EDP Sciences ble online at:https://mfr.edp-open.orgRESEARCH ARTICLEAssessment of the shear properties of thermoplastic compositesusing the 45 tension and the V-notched rail shear methodsAntonios G. Stamopoulos*, Luca Glauco Di Genova, and Antoniomaria Di IlioDepartment of Industrial and Information Engineering and Economics (DIIIE), University of L’Aquila, Montelucco di Roio,67100 L’Aquila, ItalyReceived: 4 December 2019 / Accepted: 28 January 2020Abstract. Composite materials consisting of thermoplastic matrix are gaining the interest of both theaeronautical and the automotive industry as they comprise a series of advantages regarding their mechanicalperformance, their recyclability and their ability to be produced in large quantities. Nevertheless, some notabledrawbacks have been noticed related to the fabrication process affecting their in-plane shear properties thecharacterization of which is complicated. Among the notable number of testing methods proposed throughoutthe years, several advantages and drawbacks were observed, mostly related to the way the load is applied, thestress uniformity and the applicability of each method to various material architectures. In the present work, themodified V-notched rail shear and the 45 shear testing methods are applied to short and textile glass fiberreinforced thermoplastics aiming to assess the influence of both the fabrication method and the strands direction.Consecutively, the results obtained from the two different testing methods are compared revealing a relativelygood agreement while, in parallel, the stress uniformity and the local failures observed on the specimens areanalyzed.Keywords: Shear characterization / injection molded composites / textile composites1 IntroductionAs the use of composite materials has been increasingthroughout the years by all the industrial sectors, thethermoplastic composites are gaining the interest incrementally. The main reasons are their strength-to-weightratio, their recyclability and the ability of the industry toproduce them in large quantities and volumes. Nevertheless, there has been noticed that defects related to themanufacturing process may influence significantly theirmechanical performance. These defects may be generatedin the matrix, such as porosity or delaminations [1,2] oreven in the reinforcement such as the fiber knitting ormisalignment [3–6]. These material properties’ degradationalongside with the production cost has been constantlyincreasing the skepticism of the industry towards them, forexample from the vehicle manufacturers as addressed byMangino et al. [7] while, on the other hand, the necessity ofusing more ecological, high strength and widely producedmaterials is evident.Of particular interest are the short fibre reinforcedthermoplastic composites mainly due to the fact that theycan be produced directly into the desired form using the* e-mail: antonios.stamopoulos@univaq.itinjection molding process and can be used in a variety ofapplications in which the service load is relatively low [8,9].Nevertheless, even though there has been noticed a fiberalignment towards the injection molding direction [10–12],the percentage of the aligned and intact fibers as well as therelation between the injection direction and the shearproperties is quite uncertain.Another interesting composite material category aretextile composites in which the local fibre misalignment orknitting may influence the overall mechanical behavior ofthe material [13–14]. In addition, the influence of thefabrication of a component using as primary fibredirection the warp (or the weft) on the shear behaviorof composites is also not investigated much. Nevertheless,the nature of the textile, the waviness of the strandstowards the out-of-plane direction and how the warp orweft directions, when taken as primary, influence theresult is of great interest.On the other hand, for characterizing mechanically theshear properties, until today there has been proposed asignificant number of standardized testing methods. Thedifference between them lies on their applicability ondifferent composite architectures, the way the load isapplied to the corresponding specimen, their limitationsand their universality of their application on differentcomposite material categories. In fact some standards wereThis is an Open Access article distributed under the terms of the Creative Commons Attribution License h permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
2A.G. Stamopoulos et al.: Manufacturing Rev. 7, 10 (2020)Table 1. Test matrix of the experimental campaign.MaterialLay-upSpecimen orientation5–Parallel to the injectiondirectionASTM D70708Perpendicular to the(V-notched rail shear)injection directionTextile E-glass TwillTextile Material 1 Weave fibre reinforced(47%) polypropylene[0 ]4[90 ]4[45 ]2[45 ,–45 ]WarpWeft––ASTM D7078(V-notched rail shear)5555Textile E-glassTwill Weave fibreTextile Material 2reinforced (42%)polypropylene[0 ]4[90 ]4[45 ]2[45 ,–45 ]WarpWeft––ASTM D7078(V-notched rail shear)PP-GF-30DescriptionMolded short glass fibrereinforced polypropyleneused almost exclusively for a composite material categorysuch as the 45 Tension-ASTM D3518 [15] while the loadmay by transmitted from the apparatus to the specimeneither via bending (Iosipescu) [16] or by shear excitation(Two Rail Shear ASTM D4255 [17], V-notched rail shearASTM D7078 [18]). The majority though of these standardized methods is developed mostly for unidirectional (UD)composites. For instance, the V-notched rail shear method,even though exhibits some attracting aspects such us the waythe load is transmitted from the apparatus to the specimenand its uniformity, it is not recommended for textilecomposites as it is critical to maintain the distance betweenthe two parts of the apparatus during the execution of themechanical test. On the contrary, the only establishedmethod for assessing the shear properties of textilecomposites lacks of stress uniformity on the specimen asseen in previous works [19] and according to the ASTMD3518 standard, the test should be stopped after 5% sheardisplacement for avoiding the fibre scissoring phenomenon[15].In the present work, investigated is the effect of theinjection molding direction to the in-plane shear propertiesof short fibre reinforced thermoplastic composites using amodified V-notched rail shear testing method [18].Moreover, the same testing method is implemented forassessing the in-plane shear properties of textile glass fibrereinforced thermoplastics. In parallel, the same propertiesare evaluated using the 45 tension and a straightcomparison between the two testing methods is conducted.The applicability of each method is examined as well as therelativeness of the results obtained. In addition, the effectof the textile placement towards the warp or the weftdirection of these materials is investigated. Thus, thepresent work aims not only to assess the differencesbetween standardized methods, but primarily to evaluatethe shear behavior of short and textile thermoplasticcomposite materials, introducing in parallel a modificationon the apparatus of a state-of-the-art characterizationtechnique.Standard followedASTM D3518( 45 Tension)ASTM D3518( 45 Tension)Numberof tests555552 Materials and specimensAs previously mentioned, there are two main materialcategories this work copes with, namely the short glass fibrereinforced polypropylene and the textile glass fibrereinforced polypropylene respectively. From the firstcategory evaluated is a typical commercial PP-GF-30material used in the automotive industry. As for the secondmaterial category, there are two similar textile glass fibrereinforced polypropylene composites, the main differenceof which lies to their textile architecture and themanufactures; the first one is a plain weave GFRTPwhich comes from the European market while the secondone is a twill weave GFRTP from the Asian market. Forreasons of industrial confidentiality and competitivenessthe two materials are labeled as Textile Material 1 andTextile Material 2. More details about the materials andthe corresponding specimens are presented in the followingsections. The overall test matrix is presented in Table 1.2.1 Short glass fibre reinforced polypropyleneThe polypropylene based PP-GF-30 (30% glass fibercontent) short fiber reinforced material is considered.For producing the plates of the material from which thespecimen were cut, the injection molding process wasutilized with a typical injection rate of 80 cm3/s andaverage temperature of 220 C. As previously mentioned, itis noted in numerous works a strong influence of theinjection direction on the short fibre alignment as well asthe percentage of the intact fibres remained in the materials[10–12]. This particular observation was evaluated experimentally via mechanical testing for defining the tensileproperties of these materials. Consequently, even if thepercentage of fibres that reinforces the material is relativelysmall, the material behaves more as a composite and not asa neat polymer. To this end, for evaluating the shearproperties of the PP-GF-30 material, as principal direction
A.G. Stamopoulos et al.: Manufacturing Rev. 7, 10 (2020)3Fig. 1. Schematic representation of the fibre direction related to the fabrication of the PP-GF-30 (a) and the textile thermoplasticcomposite materials (b).Fig. 2. V-notched rail shear specimen’s nominal dimensions.(0 ) is selected the direction of the injection molding. Then,the specimens are cut using waterjet cutting towards theprincipal direction and perpendicularly to it as shown inFigure 1. Therefore, the produced specimens are labelled“Longitudinal” and “Transverse” respectively. The corresponding specimen nominal dimensions are presented inFigure 2. All specimens are measured after their fabricationin order to ensure the conformity with the ASTM D7078standard [18].2.2 Textile glass fibre reinforced polypropyleneThe second material category evaluated is the textile glassfibre reinforced polypropylene. In this particular categoryassessed are, as previously mentioned, two materials, onefrom a European manufacturer and one from the Asianmarket. They are both fabricated using automatedcontinuous lamination process in which the fabric isimpregnated with polypropylene, a process which allowsthe production of a quasi-final product which practicallymeans that they are produced directly in the form of aplate. The reinforcement in both cases is E-glass twillweave textile. According to the manufacturers, eventhough the two materials demonstrate similar densities(1.67 g/cm3 for the Textile material 1 and 1.4 g/cm3 for theTextile material 2) and almost identical melting points(163 C), while the material datasheets also report similartensile properties, they have some interesting differences.More precisely, the Textile Material 1 (European) fibrecontent corresponds to 47% of the composite volume and,while the composite plate is being produced, additionalbond agent was added to the polypropylene, aimed toincrease the fibre-matrix bond. On the other hand, theTextile Material 2 (Asian) also consists of E-glass fibretextile but with two main differences namely the fibrevolume fraction, which in this case is 42%, and the absenceof additional bonding agents in the polypropylene. Theyboth have equal amount of fibres towards the warp andweft direction (50-50 warp-weft fibre weight distribution)while it is evident their difference regarding their cost; theTextile Material 1 costs significantly more than the Asianone. Therefore, even though both of them exhibit similartensile properties, their performance under shear deformation is to be investigated. To this end, for assessing the inplane shear properties using the V-notched rail sheartesting the specimens were cut from composite plates usinga high precision milling machine towards the warp(Longitudinal) and weft (Transverse) directions respectively as seen in Figure 1b. The specimen nominaldimensions are those described by the ASTM D7078standard [18] and presented previously in Figure 2. Thematerial total thickness in this case consists of 4 layers of0.5 mm each, achieving a total thickness of 2 mm so as to bein accordance with the minimum thickness of thecorresponding testing standard.For comparing the modified ASTM D7078 results withthe ASTM D3518, specimens with nominal dimensionssimilar to the tensile ones described by the ASTM D3039[19] standard were also prepared. Also in this case thespecimen categories were sub-divided into two categories:one with lay-up consisting of 2 layers of 45 and anotherone of 2 symmetrical layers of 45 and 45 . Thespecimen nominal dimensions may be observed in Figure 3.3 Experimental3.1 Modified V-notched rail shear apparatusThe standardized apparatus of the V-notched rail sheartesting method is described by the ASTM D7078 standard.It consists of 2 independent main parts in which the
4A.G. Stamopoulos et al.: Manufacturing Rev. 7, 10 (2020)Fig. 3. 45 tensile test specimen’s nominal dimensions.Fig. 4. Cross-sectional area of interest for calculating the inplane shear properties of a typical ASTM D7078 specimen.Fig. 5. Rendering of the modified V-notched rail shearapparatus.Fig. 6. Typical load-displacement curves for the PP-GF-30 and the Textile Material 1.specimen is inserted and clamped by the tabs. One part ofthe apparatus remains fixed while the other half movesalong the vertical axis away from the fixed part, intensestress is concentrated between the notches. In this case thestress may be calculated in any instant by dividing the loadby the cross-sectional area between the tips as seen inFigure 4.One of the disadvantages of the apparatus lies on thedifficulty in aligning the specimen inside the apparatus andto maintain the proper alignment of the two main partswhile testing. The corresponding standard [18] suggests theuse of proper spacers placed between the two main parts inorder to maintain the right distance and to align thespecimen before testing. From the original apparatus,Gude et al. [20] pointed the difficulty of maintaining thehorizontal distance between the two main parts during thetest and proposed a modification by adding 2 guidingcylinders which are housed in the main body in a copperring. One of the main problems of this particularmodification on the apparatus is the friction between theguiding cylinders and the main body of the apparatuswhich is developed during the testing procedure as a result
A.G. Stamopoulos et al.: Manufacturing Rev. 7, 10 (2020)5of the high horizontal forces caused by the bi-directionalcomposites. This problem practically forces the authors toremove the guiding cylinders, turning the apparatus intothe one established, by the standard, ASTM D7078. Basedon that modification, in the present work a linear rollingbearing system is added in the cylinders that minimizes thefriction between the cylinders and the main part whilebeing loaded with horizontal loads. This system is alsocapable of performing mechanical tests both in higher andbelow zero temperatures as the bearing rings exhibit lowfriction values in a large temperature range. The completerendering of the modified V-notched rail shear apparatus ispresented in Figure 5. The material used for the realizationof the apparatus is medium carbon steel C45 (ISO 6831:2018) while the low-friction bearing rings and supportsare commercial provided by the SKF.3.2 Devices and measuring systemsFor conducting the experimental campaign, the MTSCriterion 43 servo-electrical universal testing machine withload capacity of 50 kN is utilized. In parallel, for registeringthe specimen deformation during the modified V-notchedrail shear tests, a Nikon high resolution photo camera isimplemented in collaboration with the MatLab’s Ncorr[21]. The implementation of the DIC analysis is preferredeven though the corresponding standard [18] proposes theuse of strain gages. The main reason is the intensedeformation of the specimen, the creation of cracks in theregion between the V shaped notches that may detach thestrain gages. Moreover, this way the strain field may beobserved in various phases of each mechanical test, inparticular at large deformation stages.On the contrary, for conducting the 45 tensile testsfollowing the ASTM D3518 standard [15], even though thesame testing machine is utilized, implemented is an MTSstandardized extensometer placed at the center of thespecimen with a gage length of 25 mm. In parallel to that,a high resolution photo camera is placed so as topotentially observe the failure evolution of the ASTMD3518 specimen.4 Results4.1 Shear mechanical behavior and failure modesBefore analyzing the obtained material properties thatcorrespond either to the short fibre or the textile reinforcedpolypropylene materials, a correlation between the loaddisplacement curves and the failure modes of representative tests conducted with the V-notched rail shear testingmethod is presented in Figure 6. Starting with the PP-GF30 material, the behavior is non-linear and the materialarrives to the final failure with a diagonal crack causing anintense load drop as seen in Figure 6a. Regarding the shearmechanical behavior of the PP-GF-30 (30% short glassfibre reinforced polypropylene) a comparison between the“Longitudinal” and the “Transverse” specimens is observedin Figure 7a. It is obvious that there is no significantdifference of the shear behavior between the two PP-GF-30Fig. 7. In-plane shear mechanical behavior of the short fibre (a)and the textile glass fibre reinforced thermoplastic materials 1 (b)and 2 (c).specimen categories. To this end, aiming to conduct furtherinvestigation on the fractured surface of the PP-GF-30specimens, optical microscopy is implemented using aLeica M205 microscope. In Figure 8, typical Longitudinal(Fig. 8a) and Transverse (Fig. 8b) specimen fracturedsurfaces are presented, where it can be observed a largenumber of fibres oriented parallel to the x-axis. Eventhough the number of them appears to be significantly
6A.G. Stamopoulos et al.: Manufacturing Rev. 7, 10 (2020)Fig. 8. Short fibre alignment and porosity as seen in optical microscopy analysis of fractured PP-GF-30 specimens.higher for the case of specimen produced via injectionparallel to the x-axis (Longitudinal specimens), there is noabsolute orientation of the fibres; in both cases observed arefibres oriented towards the injection molding direction andperpendicular to it resulting similar properties to the twospecimen categories. Also, observed is a non-uniformdispersion of the fibres as they are concentrated mostly atthe mid-plane region. Moreover, a number of pores aredetected throughout the crack line in both the case of theLongitudinal and the Transverse specimen.On the contrary, a typical textile specimen incorporatesmore complex phenomena while being deformed as seen inFigure 6b. As indicated also in the corresponding ASTMstandard [18], in the case of textiles the fibres are beingrotated after the shear failure, allowing this way anincrement to the portion of the specimen load carryingcapacity. It is, therefore, recommended the determinationof the maximum shear load as the point in which there iseither a visual failure causing a slight load drop or a radicalincrease on the slope of the curve. During the execution ofthe V-notched rail shear tests, minor phenomena such astow cracks are observed as well as intense deformations onthe surface of the specimen, a fact that supports the use ofoptical systems (DIC) for measuring the shear deformationas this phenomenon may lead to the detachment of anystrain gage attached to it. These phenomena may be alsoobserved in Figure 9 in which specimen of the two textilecomposite materials before and after the test are presentedusing optical microscopy. Before the analysis, the specimensurface is treated with acetone in order to removeimpurities. The specimens are mostly damaged at thecentral region between the notches while the rest of thespecimen remains almost intact. As it can be seen inFigure 9, in the region between the notches a large numberof cracks at the top of the fibre strands are observed alongwith some fibre-matrix debonding or even fibre cracking inthe case of the Textile material 2. Also, especially in thecase of the Textile material 2, intense delamination isobserved at the V region.Generally, the shear behavior of these materials is nonlinear and during the mechanical test the fibres areinteracting between the warp and weft direction, increasingthe horizontal forces, favoring on the other hand, the use ofguiding cylinders for avoiding any potential horizontalrelative movement from the two parts of the apparatus.This way also, the shear strain concentration remainsconstantly concentrated at the central region of thespecimen as reported by the DIC analysis presented inFigure 10. The stress-strain curves of the two textilematerials obtained with the V-notched rail shear testingmethod for both the “Longitudinal” and the “Transverse”specimens are presented in Figure 7 b and c, respectively.
A.G. Stamopoulos et al.: Manufacturing Rev. 7, 10 (2020)7the specimen at the end of the test exhibit the previouslymentioned combination of failures quite intensively. Inaddition, two observations should also be noted, namelythe non-uniform deformation of the specimen through itslength and the intense non-uniform thickening of it as aresult presumably by a number of parameters such as theabsence of the uniformity of the shear deformation, thespecimen size and edge effects as well as the local variationsof the material structure (imperfections of the fabric or thematrix). Starting from Figure 12, obvious is a higher degreeof the textile deformation at the center compared to theregions of the specimen near the tabs. In Figure 13, ananalysis of the distribution of the shear strain of thespecimen in the region outside the extensometer isconducted revealing a non-uniform distribution of it aftera certain point before the final failure.The shear stress-strain curves obtained by theexperimental campaign using the ASTM D3518 standardfor the 2 textile materials are presented in Figure 14a and brespectively. As previously mentioned in Section 1 of thepresent work, the corresponding standard dictates theconsideration of each test of this kind as valid up to theshear strain of 5% considering the general rule suggested byKellas et al. [22] that every 2% of axial strain causes 1 ofrelative fiber rotation. Thus, even though the load increasesafter imposing 5% of shear strain, test cannot be consideredvalid after the point mentioned before, a fact which isamong the drawbacks of the 45 tensile test.4.2 Comparison between materials and standardsFig. 9. Failure modes observed in the Textile Material 1 (a) andTextile material 2 (b).Interesting observations of the failure modes during thedeformation of the 45 tensile specimen are depicted inFigure 11. Starting from the healthy specimen passinggradually from an intermediate stage prior to the failurewhere matrix cracks appear at the top of the fibre strandsdue to the relative shear deformation of the textile andfinishing with a variety of local failures such as matrixcracks, fiber-matrix debonding and intense shear deformation of textile specimen at the center of the gage lengthappear. These tow cracks in direction perpendicular to theapplied load appear all over the specimen throughout theexecution of the tests as seen in Figure 11. This type ofcracks has been reported also in previous works [19]. Thenumber of these cracks increases constantly, consequentlyIn the present section, a comparison between the resultsobtained for the 3 materials is conducted aiming toinvestigate the reliability of the testing methods, to assessthe difference between the results obtained for the samematerial using two different testing methods as well as fortwo similar textile materials tested with the same methods.Thus, the main scope is the comparison between materialsof the same kind as well as between the standards withwhich the shear properties of these materials are evaluated.All these information are presented in Figure 15 wherethe in-plane shear strength (Fig. 15a) and modulus(Fig. 15b) of the Textile Material 1 and 2 are presentedas obtained by the two testing methods. These values arealso reported in Table 2 in which the shear modulus,strength and standard deviation obtained for each materialand testing method are presented. The term shear strengthin the case of the 45 tension refers to a shear strain of 5%while in the case of the V-notched rail shear to the point inwhich a first slight drop of the curve was observed. Theresults are accompanied by a notable standard deviationfor both testing methods. Considering the restrictionsimposed by each standard described in the previoussections of the present paper, the shear strength valuesobtained by the two testing methods appear to be similarfor both the two textile materials in terms of bothmaximum stress and modulus. Nevertheless, the significantlimitation of the 45 tensile test does not allow a reliableevaluation of the shear response to such kind of materialsbeyond the shear deformation of 5% while the modifiedV-notched rail shear test, considering that contributes to
8A.G. Stamopoulos et al.: Manufacturing Rev. 7, 10 (2020)Fig. 10. Typical distribution of the shear strain obtained during the execution of the modified V-notched rail shear test on textilematerials.Fig. 11. Progressive failure of the ASTM D3518 specimen.the maintenance of the strain uniformity of the specimen, isproven useful for achieving shear deformations beyond thispoint.Moreover, even though the two textile materials exhibitsimilar shear modulus with both standards, there is asignificant difference between them in the case of themaximum shear stress obtained; the Textile material 1demonstrates higher values compared to the Textilematerial 2. Also, by examining the failure modes of theV-Notched Shear specimens, observed is an intense fibermatrix cracking development which is significantly moreintense for the case of Textile material 2. In both materials,no significant difference is observed when the specimen isFig. 12. Typical failure modes registered in the region at thecenter and lower (near the tabs) of the 45 tensile specimen.oriented towards the warp or the weft direction (Longitudinal or Transverse). Finally, for the case of the injectedshort fibre thermoplastic composite, no significant difference is observed in both the in-plane shear strength andmodulus obtained from the specimens cut in parallel orperpendicular to the injection molding direction.5 ConclusionsIn the present work, a variety of GFRTPs’ in-plane shearmechanical behavior was characterized experimentallyusing two of the most frequently used testing methods.
A.G. Stamopoulos et al.: Manufacturing Rev. 7, 10 (2020)9Fig. 13. Distribution of the shear strain in the regions above and below the specimen center during the execution of the 45o tensiletests for the textile composite materials.Table 2. Obtained in-plane shear properties of all materials tested according to the two testing earShearStandard deviationstrength** deviationmodulus of shear modulus[MPa]of shear[GPa][GPa]strength [MPa]Parallel to theinjection direction23.61.11.9450.17319.72.122.0140.201ASTM D70708 Perpendicular tothe injectiondirectionWarpWeft62.536.752.0410.228ASTM D707858.889.362.0340.504ASTM D351845 45 2.581.683.352.2812.2502.0260.3110.1370.328ASTM M D351845 45 39.0540.061.293.002.1712.1370.1020.275Textile Material 1Textile Material 2*Specimenorientation*In the case of the ASTM D3518 specimen orientation refers to the 2nd layer direction.In the case of the tests conducted using the ASTM D3518 method, shear strength refers to the shear stress at 5% shear strain.**
10A.G. Stamopoulos et al.: Manufacturing Rev. 7, 10 (2020)Fig. 14. Shear mechanical behavior for the Textile Material 1 (a)and 2 (b) obtained by the 45o tensile test.Starting with the injection molded short glass fibrereinforced polypropylene, the V-notched rail shear testingmethod was successfully applied in specimens cut towardsboth the longitudinal and the transverse direction of theinjection. By comparing the results, no significant difference was observed for the two specimen categories. As forthe second material category, the V-notched rail sheartesting method was implemented and its results werecompared with the more conventional 45 Tension test.Moreover, two similar materials with different provenanceand slightly different fibre content were compared. Formaintaining the proper alignment of the components of thestandardized apparatus, a modification was proposed on it.As the main objective was the investigation of theinfluence either of the injection direction (for the case of theinjected short fibre composite) or the textile fabricationdirection (for the case of the textiles), no significantdifference was observed regarding the shear strength ormodulus. Nevertheless, some differences were observedregarding the shear strength of the two textile materials.For the case of the short fibre composite, the injectiondirection, perpendicular or parallel to the specimen length,does not appear to influence significantly the shearperformance of the material.Fig. 15. Comparison of the shear standards and materials interms of shear strength (a) and modulus (b).Finally, by comparing the state-of-the-art standardized testing methods was conducted revealing theadvantages and disadvantages of them and their abilityto predict the shear mechanical performance of differentcomposite materials.
For comparing the modified ASTM D7078 results with the ASTM D3518, specimens with nominal dimensions similar to the tensile ones described by the ASTM D3039 [19] standard were also prepared. Also in this case the specimen categories were sub-divided into two categories: o
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Shear Stress vs Shear Displacement 0 20 40 60 80 100 0 2040 6080 100 Shear Displacement (mm) Shear Stress (kPa) Normal Stress - 20.93 kPa Field id: MID-AAF-0002-1 Measured Cohesion 14.99 Water Content 5.62 Shear box size 5.08 Peak Shear Stress 31.34 Intrinsic Cohesion 14.45 Wet Density 2240 Matri
Concrete contribution to the shear force capacity of a beam [N] V d Design shear force [N] V s Steel stirrups contribution to the shear force capacity of a beam [N] V p Axial load contribution to the shear force capacity of a beam [N] V i Other contributions to the shear capacity of a beam [N] V frp FRP contribution to the shear capacity [N]
