Water Absorption and Flexural Test for Glass Fibre Reinforced Polymer - Case Study Example

WATER ABSORPTION AND FLEXURAL TEST FOR GLASS FIBRE REINFORCED POLYMER (GFRP) by Physical address Experimentation: Water absorption and flexural test for Glass Fibre Reinforced Polymer (GFRP) Abstract It will be examination of the time dependence of water absorption by immersing the samples of Glass fibre-reinforced polyester (GFRP) in salt and normal water, after that measuring the mass of the specimens at specific moments. After that a flexural test will be done using a three point bending method. The main objective of this experiment is to expand the knowledge about the GFRP and its behaviour. Glass fibre reinforced unsaturated polyester (GFRP) were subjected to water immersion tests to know the results of the water absorption on the mechanical properties. 20 specimens with 10cm long of GFRP were used to this experiment, measuring their weight under different types of water and temperatures. Salt water and normal water was under 20c and 60c temperatures. The weight of these specimens was taken during a different time periods. The weight of the GFRP specimens was increased slightly in both types of water for a few days until it was stable. After that a flexural test (three point bending test) was done on these GFRP specimens. (H Dhakal, Z Zhang, M Richardson, 2006) Equipment 1: Water absorption test The absorption of water for the Glass fibre-reinforced polyester (GFRP) remains the key mechanism for degrading mechanical property in this experiment. A water bath machine as in the figure (ten) and two cups of glass as on the figure (eleven) were used in this experiment. The water bath has 6oc water and the two cups were at 20c water temperature. Figure ten: water bath machine at 60c Figure eleven: GFRP specimens at 20c Experiment 2: Flexural test The flexural test was done by a flexural machine as on the figure (twelve). The flexural strength and modules of the composite after the water immersion were determined using three point bending method. The main objective of this test is to know how the temperature and the sea water effects the flexural of the GFRP specimens ( H Dhakal, Z Zhang ,M Richardson ,2006) Figure twelve: flexural machine Experimentation procedures 20 specimens of GFRP were used in 4 groups. Group 1 and 2 were in two jars marked with A and B as on the figure (thirteen). Jar A was containing fresh water and jar B was containing salt water. The 2 jars were inside a water bath machine at 60c water temperature. Group 3 and 4 were in two cups of glass marked with A and B as on figure (eleven). Cup A was containing fresh water at 20c and cup B was containing salt water at 20c as well. Every group has five specimens. The weights of one single specimen from each group were taken in a different time periods using a sensitive scale as on figure (fourteen). At the first day the weight was taken every hour for 6 hours. After that the weight was taken once every day until the weight is settled. At the end the flexural test was done for all the specimens and every specimen has its own flexural graph. Figure thirteen: jars at 60c temperature Figure fourteen: sensitive scale Results and Discussion: Water absorption test Water absorption test were conducted by immersing the GFRP specimens in de-ionised water and salt water. The water bath machine at 60c was containing 2 groups, group 1 was in A jar containing a normal water and group 2 was in B jar containing a salt water. Groups 3 and 4 were at 20c in a glass cups group 3 was in A glass cup containing a normal water and group 4 was in B glass cup containing a salt water. The immersion for the specimens into the water was totally for 144hr. after immersion for 1hr, one specimen from each group were taken out of the water and all surface water was removed with a clean soft dry cloth. The specimens were weighed regularly at 1, 2, 3, 4, 5, 6, 24, 48, 72, up to 144hr. ( H Dhakal, Z Zhang ,M Richardson ,2006) After immersion the GFRP specimens into the water for a week at ambient temperature at 60c and 20c, all the specimens were dried in a room temperature group 1 and 2 specimens at 60c they haven’t changed in colour and appearance in the first few hours, the same was for the group 3 and 4 at temperature of 20c, however the weight for the specimens of all groups was increasing. A graph of mass against time for all groups When the GFRP specimens are immersed in de ionized and salty water, they absorb water through diffusion. The amount of water absorbed increases with increase in time at the same temperature. This is evident from progressive increase in specimen masses. For instance, the mass of specimen immersed in de-ionized water increases from 12.83494g at t= 1hr to 12.92457g at t =72hr when temperature is kept constant at 20oC. However, more water is absorbed in salty condition. For example the change in masses for specimen immersed in de-ionized water and salty water at 20oC between t = 2hrs to t =120hrs is 0.06206g and 0.09084g respectively. When temperature is increased, the water absorption is accelerated both for specimen I de-ionized and salty water. For instance, the change in mass of specimen placed in salty water at 20oC between t = 1hr to t = 5hrs is 0.04995g. The corresponding change in mass at 60oC is 0.09900g. The increase in temperature is proportional to degradation or amount of moisture absorbed by GFRP. Higher temperature means larger quantity of heat. This heat causes expansion of both the fibre and matrix. Since, the two materials have different expansion rates, gaps emerge at the interface where the two are bonded. These pores take in more water into the GFRP resulting in large change in mass at high temperature. Flexural test The flexural test was made by a flexural machine using a 3 point bending method. The 4 groups had a different flexural strain results Theoretical Values Series Emod F at 0.1% plastic deformation F at 0.2% plastic deformation Upper yield point dl at upper yield point Fmax GPa N N N mm N x 28.37401 3026.516 3000.532 3125.698 3.737538 2784.072 s 0.469676 41.63588 87.4253 88.03177 0.280158 666.125  1.655302 1.375703 2.913659 2.816388 7.495802 23.92628 dL at Fmax FBreak dL at break a0 b0 S0 mm N mm mm mm mm² 4.455869 937.5601 7.497742 8 8 64 1.571792 26.36941 1.077328 0 0 0 35.27466 2.812557 14.3687 0 0 0 Results Emod F at 0.1% plastic deformation F at 0.2% plastic deformation Upper yield point dl at upper yield point Fmax dL at Fmax FBreak GPa N N N mm N mm N Specimen 1 28.33222 3086.029 3111.097 3159.573 3.908794 1793.069 6.782115 947.6539 Specimen 2 28.5916 3007.598 2909.853 3056.838 3.366292 3056.838 3.366292 917.0278 Specimen 3 27.73966 3021.664 3024.387 3051.682 3.682104 3051.682 3.682104 915.3193 Specimen 4 28.83258 2990.775 2956.792 3234.699 3.992962 3234.699 3.992962 970.2392 dL at break a0 b0 S0 mm mm mm mm² 8.984636 8 8 64 6.405447 8 8 64 7.307097 8 8 64 7.293787 8 8 64 Deformation Force Deformation Force Deformation Force 0.003258 18.83624107 0.064782 79.27963855 0.13458 122.0039743 0.196226 164.2578257 0.257878 209.4398635 0.319527 257.4792217 0.381177 307.2122646 0.442828 358.1180964 0.504478 410.2936789 0.566128 463.3953725 0.627778 517.3608102 0.689426 571.5433086 0.75108 626.3495879 0.812727 682.0536697 0.874377 737.8259228 0.936029 794.6527496 0.997677 852.2619678 1.05933 910.2728667 1.120978 968.7786007 1.182625 1027.70877 1.244279 1087.013979 1.305919 1146.677272 1.367575 1206.492415 1.429225 1266.575403 1.490874 1326.473913 1.552524 1386.458315 1.614176 1447.161935 1.674888 1506.842797 1.735808 1566.911519 1.797453 1627.862852 1.85911 1688.753626 1.920753 1749.819672 1.982406 1810.838105 2.044057 1871.761587 2.105705 1932.678035 2.167354 1993.488242 2.229007 2054.177025 2.290653 2114.395877 2.35231 2174.705124 2.413957 2235.117471 2.475605 2294.940469 2.537258 2354.705844 2.598903 2413.976246 2.660557 2471.797066 2.722205 2529.662809 2.783853 2587.724629 2.845504 2645.552979 2.90715 2703.435732 2.968803 2760.727935 3.030453 2817.307195 3.092102 2872.603997 3.159771 2925.425366 3.224568 2976.696249 3.286217 3029.17076 3.375246 3023.626696 3.458674 3008.891252 3.520337 3055.84862 3.581796 3082.032642 3.668513 3101.109923 3.807753 3125.850797 3.914126 2846.010449 3.96807 1018.903329 4.032607 1065.599431 4.120528 1113.692386 4.212993 1157.48328 4.308056 1198.41395 4.419242 1242.22395 4.54152 1288.15434 4.66678 1332.375079 4.792294 1375.920813 4.916136 1418.481584 5.039724 1460.394921 5.163021 1501.778845 5.28475 1541.173224 5.410812 1580.591342 5.547599 1621.841945 5.697865 1664.67974 5.867961 1705.209067 6.070028 1731.421621 6.32246 1758.942505 6.640812 1783.87856 6.907869 1773.794394 7.002887 1723.795588 7.044522 1670.994302 7.091524 1618.609748 7.12994 1567.850104 7.173819 1515.622298 7.231314 1454.851886 7.300407 1402.295773 7.379765 1356.371077 7.494538 1313.774041 7.618394 1271.488126 7.725081 1227.5174 7.830353 1184.990314 7.969798 1141.939361 8.174892 1103.102011 8.435815 1070.430638 8.678512 1034.24161 8.877209 993.2966193 4.837717 948.7999779 Deformation Force Deformation Force Deformation Force 0.00258 17.97498 0.055828 73.45234 0.119528 112.194 0.174077 150.4554 0.228622 191.4745 0.283171 234.0907 0.337709 277.6916 0.392256 322.3108 0.446801 367.9431 0.501352 414.5738 0.555894 462.0194 0.610437 510.1478 0.664985 558.6858 0.719528 607.3789 0.774074 656.9192 0.828616 706.7846 0.883163 757.1705 0.937705 808.2999 0.992254 859.9843 1.046802 911.9292 1.101351 963.8161 1.155892 1016.235 1.210439 1068.687 1.264983 1121.611 1.319529 1174.51 1.374076 1227.7 1.428617 1280.812 1.483167 1333.603 1.53771 1386.507 1.592256 1439.764 1.646577 1492.815 1.700514 1545.367 1.755057 1598.639 1.809607 1651.733 1.864151 1705.011 1.9187 1757.931 1.973246 1811.139 2.027784 1864.001 2.082335 1916.899 2.136872 1969.735 2.191425 2022.425 2.245969 2074.986 2.300517 2127.183 2.355061 2179.703 2.40961 2231.781 2.464152 2283.766 2.518696 2335.435 2.573241 2386.972 2.627786 2438.227 2.682333 2489.028 2.737326 2539.109 2.795591 2587.06 2.850136 2637.069 2.904676 2686.766 2.959222 2736.405 3.01377 2785.516 3.068318 2832.922 3.12286 2880.927 3.177411 2928.796 3.231951 2975.609 3.292775 3018.282 3.362974 3039.166 3.439393 3006.198 3.4828 2929.268 3.523794 2856.071 3.561503 2630.261 3.600519 2526.044 3.648168 2480.635 3.676664 2426.292 3.703916 2355.908 3.731206 2140.43 3.758793 2038.287 3.806948 1991.193 3.875066 1947.814 4.042712 1915.619 4.233032 1883.881 4.34825 1845.912 4.399608 1795.545 4.431072 1743.816 4.493807 1702.36 4.570923 1662.169 4.627006 1615.492 4.692371 1573.487 4.754581 1531.608 4.815384 1491.372 4.884796 1451.336 4.972937 1413.302 5.082881 1375.689 5.187537 1337.404 5.271489 1298.004 5.38622 1260.468 5.516868 1223.493 5.612817 1184.261 5.699554 1144.998 5.77856 1106.092 5.889116 1068.706 6.006838 1030.783 6.166936 995.8735 6.285266 955.6317 3.478827 918.2129 Deformation Force Deformation Force Deformation Force 0.002632 17.607 0.057585 71.78843 0.134637 115.2292 0.192083 151.7001 0.247348 189.525 0.30262 229.9911 0.357887 272.692 0.413159 316.9169 0.468422 362.2434 0.523696 408.3288 0.578966 455.2102 0.634237 502.6901 0.689505 550.3891 0.74477 598.2299 0.80004 646.7312 0.855307 695.5954 0.910583 744.9196 0.965846 794.8652 1.021125 845.3892 1.076389 896.2948 1.131661 947.3201 1.186932 998.8029 1.242195 1050.448 1.297464 1102.531 1.352737 1154.561 1.408006 1207 1.463271 1259.526 1.518546 1311.968 1.573815 1364.191 1.629085 1416.921 1.684353 1469.763 1.738201 1521.098 1.793225 1573.772 1.848491 1626.515 1.903765 1679.507 1.959031 1732.035 2.014304 1784.921 2.069572 1837.87 2.124846 1890.476 2.180111 1943.307 2.23538 1995.809 2.290648 2048.35 2.345918 2100.465 2.40119 2152.596 2.456456 2204.491 2.511728 2256.292 2.566994 2307.455 2.622266 2356.759 2.677529 2405.992 2.7328 2455.544 2.788071 2505.328 2.843339 2555.528 2.898614 2606.449 2.953879 2657.063 3.009156 2707.737 3.064418 2757.98 3.120376 2807.402 3.177458 2854.046 3.232728 2901.696 3.287539 2944.178 3.345051 2919.546 3.402705 2960.545 3.45797 3005.221 3.512926 3032.264 3.629109 3034.604 3.721146 3018.249 3.810623 2982.649 3.905308 3006.956 3.95627 2667.493 3.983896 2254.035 4.011541 2180.429 4.039159 2118.193 4.066812 2052.177 4.102636 2003.52 4.135417 1937.861 4.163028 1846.692 4.191111 1779.949 4.239834 1734.88 4.354564 1696.638 4.495573 1660.398 4.629477 1623.312 4.724469 1583.189 4.79178 1539.374 4.858886 1496.813 4.937256 1456.074 4.999176 1411.787 5.074746 1372.247 5.132201 1330.872 5.217835 1292.449 5.286684 1249.452 5.441068 1213.107 5.664725 1180.794 5.804686 1143.263 6.022021 1110.996 6.267509 1081.039 6.522448 1051.209 6.754762 1017.094 6.956532 981.4305 7.093654 943.0044 3.957539 915.889 Deformation Force Deformation Force Deformation Force 0.002647 17.32643 0.056149 70.6578 0.129595 112.0617 0.185823 148.6703 0.240115 187.6443 0.29441 228.8554 0.348695 271.9573 0.402997 316.6019 0.457285 362.6273 0.511582 409.74 0.565873 457.9305 0.62017 506.4806 0.674461 555.1483 0.728749 603.9119 0.783047 653.3563 0.837335 703.1333 0.891633 753.5434 0.945926 804.6179 1.000222 856.2513 1.054515 908.4505 1.108808 960.7612 1.163097 1013.574 1.217386 1066.649 1.27168 1120.126 1.325973 1173.492 1.380267 1227.213 1.434561 1280.761 1.488856 1334.248 1.543146 1387.799 1.597438 1441.816 1.651441 1495.719 1.705193 1549.414 1.759484 1603.777 1.81378 1657.922 1.868074 1712.136 1.922369 1766.126 1.976656 1820.299 2.030948 1874.165 2.08524 1928.282 2.139535 1982.131 2.193829 2036.1 2.248121 2089.716 2.302419 2143.175 2.356705 2196.96 2.411001 2250.214 2.465294 2303.585 2.519584 2356.601 2.57388 2409.439 2.628175 2461.628 2.682467 2512.763 2.736761 2562.032 2.791051 2612.985 2.843575 2646.595 2.897971 2667.76 2.952262 2714.947 3.006558 2763.338 3.06085 2810.635 3.115145 2855.179 3.169437 2901.022 3.223728 2946.856 3.27802 2992.061 3.332313 3034.801 3.386663 3050.679 3.424692 2994.589 3.50335 2962.324 3.581492 2986.198 3.637943 3023.322 3.692238 3060.96 3.74653 3098.044 3.800828 3134.093 3.857515 3169.769 3.934303 3210.097 4.00868 3190.21 4.041305 3049.339 4.068474 2050.335 4.101323 1836.015 4.277553 1808.776 4.498681 1786.199 4.579969 1744.556 4.635422 1702.998 4.705127 1661.687 4.804518 1624.008 4.91427 1586.928 5.027211 1549.951 5.132938 1512.14 5.220912 1473.629 5.315614 1435.49 5.423521 1398.481 5.537644 1360.845 5.694973 1325.146 5.886529 1290.251 6.073325 1255.225 6.202317 1218.361 6.315852 1178.717 6.559303 1152.653 6.761047 1118.369 6.923547 1082.931 7.076156 1046.654 7.202916 1008.618 3.962996 971.7005 The mechanical properties of GFRP are affected by both temperatures and moisture content. The tensile stress and strain are reduced exponentially when GFRP are exposed to moisture. For instance, the modulus of elasticity for specimen 1 reduces to 99.85%. This change is caused by reaction involving the solutions, matrix and the fibre. The solutions diffuse and collect in between the interface of the matrix and fibre. The water hydrolyses the resin causing it its chain to rapture. The alkaline solution on the other hand dissolves the glass fibre leading to reduced toughness. When the interfacial regions, considered to be weak points, are degraded, the whole mechanical properties of material are changed. This reactions are speeded up by increase in temperature thus GFRP materials ages faster. The difference in thermal properties of glass and resin generate shear stress when the materials are heated. Thus gaps are created at the interface due to deboning. This explains why the change in tensile strength is high at higher temperatures. Read More