Originally Posted by
peteeng
Hi Spot - Again sorry - the fibre composite industry has very specific definitions of weaving, knitting and tape laying,. I have been involved in all of these. The machine in the video is a tape layer. The tape is prepreg epoxy and carbon fibre. The resin is formulated for a specific "tack' so it is heated via an infra red element that you can see the glow from. It comes off the roll and is just like sticky tape. There is no stitching thread (sewing) or intertwining of fibres (knitting).
I suggest you read up on mechanics of solids... There is enough weight of evidence that Portland cement cracks and that every civil design code is based on the concrete cracking so the code has to mitigate the cracking issue with "reinforcement" which is a poor descriptor for what it does. FEA is only as good as your assumptions used and the interpretation within those assumptions. A manual calc is as good for something simple...
I have tested many materials personally or at labs. Concrete or grout - I have various samples that I have used for stepping stones around the place... some are quite expensive! steps...
Your saying that 0.25m3 is $35 USD and that 91.2kg od steel is $105 USD. So take your concrete at 2400kg/m3 is 600kg so concrete is 0.058 $/kg and steel is $1.15 per kg.
around here concrete cost around $250/m3 laid so thats 0.25 $/kg. At the hardware 20kg of cement costs $8 AUD so that makes 26kg of concrete so thats 0.31 $/m3
I'll use $0.10 USD / kg and steel at $1.00 USD/kg so the maths is easy.... Peter