Slide 1
A composite gives different materials different jobs
A composite combines distinct materials with complementary roles. In a fibre composite, the reinforcing fibres and surrounding matrix do different jobs.
The matrix holds the fibres and transfers loads between them.
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The fibres often carry much of the load along their length. The matrix holds their arrangement, transfers loads between them and protects them from parts of the environment.
Slide 2
Aligned fibres make direction part of the design
Aligned fibres give strong directional properties. A component can be efficient along one direction while weaker in another.
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Layers with different orientations can carry loads from several directions. The stacking sequence also affects bending and coupling, so two laminates with similar fibre content need not behave identically.
Slide 3
The interface transfers load to the fibres
Loads must pass between fibres and matrix through their interface. Poor bonding can prevent the reinforcement from doing its intended work.
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Voids, contamination or unsuitable surface treatment can weaken that transfer. Manufacturing quality therefore influences performance even when the chosen fibre and resin have excellent individual properties.
Slide 4
Layers can separate without obvious surface damage
A laminate can delaminate, separating internally between layers. Surface appearance may not reveal the full extent of impact damage.
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Inspection methods need sensitivity to the relevant internal damage. A repair also has to restore the intended load path and geometry, rather than simply cover the visible mark.
Slide 5
Low mass is only one part of the material choice
Composites can provide useful stiffness or strength for their mass. Cost, temperature, fire behaviour and end-of-life handling also shape the decision.
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Joining a composite to metal introduces load-transfer and thermal-expansion questions. The best material at the coupon level is not automatically the best assembled system.
Sources
- What Is a Composite Material?
TWI
- Stresses in Beams
MIT / David Roylance