Fibre volume fraction
Round fibres can never fill a ply (78.5% square, 90.7% hexagonal packing); real prepregs sit near 56–57%. By mass the number reads higher (56% by volume is 65% by mass for M56 UD134). Along the fibres, stiffness rises almost in step: 50 → 60% fibre gives about a fifth more E1.
Predict · at 0:53 in the video
Raise the fibre volume from 50 to 60 percent. Roughly how much stiffer does the ply get, along the fibres?
About a fifth. For AS4 in 8552, from 118 to 140 gigapascals. Along the fibres it's almost a straight line: more fibre, more stiffness.
This course is our own. These books go deeper.
- Basic Mechanics of Laminated Composite Plates, A. T. Nettles, NASA Reference Publication 1351, 1994
- Mechanics of Composite Materials, R. M. Jones, Taylor & Francis, 2nd ed., 1999
- Engineering Mechanics of Composite Materials, I. M. Daniel & O. Ishai, Oxford University Press, 2nd ed., 2006
- Design and Analysis of Composite Structures, C. Kassapoglou, Wiley, 2nd ed., 2013
- Composite Materials Handbook (CMH-17), Volume 3, Rev. G, CMH-17, SAE International, 2012
The course designs in AddPly, our browser app for laminate design: regions, ply stacks with live stacking-rule checks, thickness, mass and the ply book. It does not do strength, failure or draping; where a lesson covers those, the simulation is our own.
Simulations in this lesson are our own. Ply data come from the datasheet or textbook named on screen; where a number rests on an assumption, the video says so.
