Dear All
I have made a 4-layer woven glass fiber epoxy composite plate 8 months ago (hand-layup method) and I extracted all of its mechanical properties by experimental tests and theoretical calculation. I put the plate in our Lab exposed to air and I have been working on it. but I accidentally found out that its mechanical properties have changed and it is vivid when a guided wave propagates in it. (the Group Velocity has changed and as the plate has a pre-made defect in it, The results related to damage also have changed). I was wondering what might be the reasons of this phenomenon and I appreciate if any one introduces me related papers about the influence of time on composite plates.
Many thanks
Although this strange to here about GFRP Plates, but anyhow, infrared vilots is the only harmful thing on glass fabrics. If cured (maximum 7 days) and protected by protection material, time does not affect GFRP epoxy composits.
Dear Professor Elsayed
Thank you so much for answering. the plate was just exposed to air and there was not protection materials. Do not you think that these changes are related to epoxy property? I mean by getting dry the epoxy properties changed
Sure, thanks professor
I used to get signals from damage part much more less than healthy part in amplitude but after at first days of manufacturing of plate but after 16 weeks of manufacturing, I repeated the same experiment and this time signals related to damage part was almost as same as healthy part in amplitude. (the reduction was eliminated) the damage is a predefined rich resin area between 2th and 3th layers.
(And sorry professor for late answer, Researchgate did not send me the notification)
Thus, curing was developed and took place during this time period. This seems to be logic.
Dear Professor Elsayed
Thank you so much for the help. It helps me a lot
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