Young s modulus measurement of wood and CFRP

Transcription

1 Deiverae WP D.4 First Detaied Design and Laoratory Testing 7-1 Young s moduus measurement of wood and CFRP Viet An Nguyen, Roert Le Roy, Jean-François Caron 1. Ojetives Te ojetive is to arry out ending test on two wood-omposite eams and a wooden eam to estimate te wood and CFRP (denoted as aron ereafter for te sake of simpiity) easti properties vaues, i.e. te Young s moduus, and te sear moduus G. A diret tension experiment is aso onduted on a sma aron oupon taken from one of te wood omposite eam. Tree and four point-ending tests were reaized on different eams. Measurements of strain and dispaement were reaized y gauges and sensors paed in positions su as tere is no order effet (wood knot). Te apaity of te maine is 1 kn. Te oad appied varies etween 5 to 18 kn for te ending tests.. Bending test devie.1. Four point ending test F/ F/ 198m a,6m 1,78m a,6m 9m apteurs Figure 1. Four point ending test : dimensions.. Tree point ending test F 9m apteurs 78m Figure. Tree point ending test : dimensions. Anaysis of resuts. Maximum appied oad is equa to approximatey 4% of te utimate oad, so tat te materia is kept in te easti range. a oading onsists of 4 yes. Te Young s moduus and te sear moduus G of materias are dedued. or LCPC PAG : 1 OF 6 Fie : Deiv_4_LAM_Annex.do

2 Deiverae WP D.4 First Detaied Design and Laoratory Testing Determination of wood s Young moduus y pure ending tests. For te 4 point ending tests of a wood guam (GL) ea te foowing metod desried in te standard NF-48 is detaied eow : 1. m, R M M m, R. P. a 1 w P. a 1 ( + ) (. 8. w. 8. w P. a 1 m, 16. w m, + were,, M, R are, respetivey, te oa average moduus, inertia of setion, ending moment and radius of urvature. Te measures are taken in te entra zone, were te ending moment remains onstant. Te dimensions are given on te figure 1: ) 1 1 y 149x - 496,69 R, ,1,,,4,5,6,7 Figure. Fore (N) versus reative defetion (mm) 4points ending test of wooden eams, setion 18x9m ² Tree suessive tests were arried out on te same eam for oads varying from to 1N. Te Young s moduus of wood was found etween 1. to Te auation is detaied in Tae 1.. Determination of wood sear moduus. Ten a point-ending test was onduted on te wooden eam of.1. Te part of te defetion generated y te sear fore is te differene etween te tota defetion and te defetion generated y pure ending moment. Tus: F. F. F. d 4. G. S app or LCPC PAG : OF 6 Fie : Deiv_4_LAM_Annex.do

3 Deiverae WP D.4 First Detaied Design and Laoratory Testing 7-1 finay, k G 4. G.. 4. app kg G k G 1 1.( app may e otained y te foowing formua : app.. G app. 1 ) m, app 1 ( F F1 ) 48..( w w ) 1 were k G te setion fator, k G 1, for retanguar setions y 1159x - 579, R,9898,,4,6,8 1 1, Figure 4. Fore (N) versus reative defetion (mm) - points ending test of wooden eams, setion 18 x 9m ² n tis test, te wood sear moduus was measured etween 575 MPa and 5 MPa wen te moduus varies respetivey from 1. to Te resuts are detaied in Tae 1.. Determination of CFRP s Young moduus, ayered on te intrados of te wood eam We ave done two 4 point-ending tests on two wood-omposite eams, one reinfored wit 1 ayers of unidiretiona CFRP, te oter wit 1 ayers. To simpify te anaysis, equivaent dimensions were assiay introdued (see figure eow). quivaent widt : eq quivaent wood setion in T-sarp to sandwi setion eq eq eq. 1 1 or LCPC PAG : OF 6 Fie : Deiv_4_LAM_Annex.do

4 Deiverae WP D.4 First Detaied Design and Laoratory Testing 7-1 eq is a funtion of and. Troug te tests, eq is auated to dedue te modue of aron. quivaent sandwi setion: axe neutre axe neutre eq..1 Determination of aron s moduus using a strain gauge at mid-span. Te strain of te ower fier is measured and potted as a funtion of oad (fig.5). Hene te urvature, and te equivaent fexura rigidity () eq are dedued, and ten te omposite Young s moduus. On te eam wit 1 ayers of aron, te Young s moduus of CFRP varies etween 94 and 86 were varies etween 1. and Wit 1 ayers, CFRP Young s moduus varies etween 14 and 111. t seems tat a sae effet is introdued during wrapping. 5 y 17x - 84,11 R,9949 1,5,1,15,,5,,5 Figure 5. Fore (N) versus strain at mid-span (x1 ) - 4 points ending test of wood-omposite eams, setion 1 x 9 m ².. Determination of aron s moduus wit tree dispaement transduers. By tis metod of measurement, te eam wit 1 ayers of aron, te Young s moduus of aron varies etween 11 and 81 wen varies etween 1. and For 1 ayers, te aron Young s moduus varies etween 116 and 95.4, respetivey. (see resuts in Tae ). or LCPC PAG : 4 OF 6 Fie : Deiv_4_LAM_Annex.do

5 Deiverae WP D.4 First Detaied Design and Laoratory Testing y 1147x + 177,71 R,9989 8,1,,,4,5,6,7,8 Figure 6. Fore (N) versus reative defetion (mm) 4 points ending test of wood-omposite eams, setion 1x9m ² Te resuts for te two eams are sigty different. Te resut for te 1 ayers eam is oser tan te moduus dedued from te foowing tensie test performed on a singe sampe of 5 ayers. 4. Diret tensie test. A aron sampe, m ong and wit a widt of aout 1 m was taken from te wood-omposite eam. Ony 5 ayers were gued on te intrados of te GL eam. Te setion is 7.8 mm² orresponding to a tota tikness of 1.8 mm (ayer tikness.6 mm) and a widt of 1 mm. Te ongitudina and transverse strains were measured using strain gauges. Te foowing resuts were otained: ongi 9.4 ν LT.1 ontrainte de tration et déformations ontrainte (Pa) %.% %.4%.6% sigma(defo axiae) sigma(defo transverse) déformations Figure 7. Stress (Pa) versus ongitudina strain (ue) and transverse strain (pink) during diret tensie test or LCPC PAG : 5 OF 6 Fie : Deiv_4_LAM_Annex.do

6 Deiverae WP D.4 First Detaied Design and Laoratory Testing 7-1 Syntesis Te resuts are summarized in te foowing taes. Tae 1 gives te vaues for te wooden eam in referene and reversed position (were are reversed intrados and extrados, tensie and ompression ords). Tae sows te vaues of CFRP moduus for te eam of 1 (P1) and 1 aron ayers (P1). Te wood GL setion of te reinfored eams is not exaty te same as te one of wooden eam. t is assumed tat te moduus of wood is te same for a eams (tey are GL8 ass oming from te same deivery). Wooden eam Cye 1 Cye Cye xe fies Referene P_BOS_18X9_4P_917_1kN_.xs position G, Fexp_ois_18x9x78_517.xs Reverse position P_BOS_18X9_4P_917_1kN_1.xs Tae 1 : ongitudina Young s moduus and sear moduus vaue of wood Note: Te vaues of G (detaied in te fie fexp*.xs) are auated wit 1.79 Reinfored eam Cye 1 Cye Cye xe fies 9,5 18 P1 sensor 87 ois_omp_9x1_1oues_4p_ending.xs gauges ois_om_1_jauge_a_miieu_41.xs P sensor ois_omp_9x1_1oues_4p_ending.xs gauges ois_om_1_jauge_a_miieu_41.xs Tae : Caron Young moduus vaue, otained wit an average wood moduus 179Mpa, Te data proessing was arried out onsidering tat te tikness of ea aron ayer is.6mm. Te diret tensie measurement wit ayer tikness e.6 mm for te sampe of 5 ayers gives te foowing resuts: ongi 9.4 ν LT.1 Finay, a mean vaue of tota measurement was osen as: ongi 98 or LCPC PAG : 6 OF 6 Fie : Deiv_4_LAM_Annex.do