How the lay-up in composite materials affect to its mechanical properties?
A laminate is constructed by stacking a number of laminas in the thickness (z) direction. Because of its utiliy, laminate stacking sequence in composite materials are commonly used. There can be more than a thousand of combinations of laminates stacking sequences (LSS), each one with different characteristic attending to the following variables:
- Number of plies
- Thickness
- Material
- Orientation
- Sequence
Most laminate stacking sequence used
Depending on these variables and how they are combined it will define the final properties of the laminate. The following laminates are the most common one used.
- Unidirectional laminate: all the laminas have the same orientation angle. Usually are 0º laminates. Example: [0/0/0/0/0/0]
- Angle-ply laminate: the fiber orientation angles are in alternate layers. For example, /-30/30/-30/-30/30, but 0º and 90º are not allowed.
- Cross-ply laminate: fibers orientations angles are in alternate layers and only can be 0º and 90º. Example: [0/90/0/90/0/0/90]
- Balanced laminate: for each laminate with an orientation angle, exists another with a a negative orientation. Example [0/45/-45], [-30/30].
- Symmetric laminate: the ply orientation is symmetrical about the centerline of the laminate. For each ply above the midplane, there is and identical ply at an equal distance below the midplane. Examples: [0/+45/90/90/+45/90] or [0/45/90]s
- Antisymmetric laminate: the ply orientation is antisymmetric about the centerline of the laminate. To compare with the symmetric, this is a symmetric laminate X/-X/-X/X and this an antisymmetric laminate X/-X/X/-X. An antisymmetric laminate is a balanced laminate too.
- Quasi-isotropic laminate: these types of laminates need three of more plies with identical thickness and material with equal angles between each adjacent lamina. Quasi-isotropic laminates are symmetrical and balanced. Examples: [0/60/-60]s or [0/45/90/-45]s. A very common and widely used quasi-isotropic symmetrical stacking sequence is [0/±45/90].
As commented in previous posts, depending on the laminate stacking sequence in composite materials lay-up, the ABD matrix will be different, which directly affects to the mechanical properties of the laminate.
