What are continuous fibers?
A continuous fiber is characterized as having a very high length-to-diameter ratio and provides superior mechanical properties when compared to discontinuous or short fibers. These fibers can be woven into a fabric with warp (0°) and weft (90°) angles, or uni-directional, where all fibers are aligned in the 0° direction.
In a composite material, the fiber determines the strength and stiffness of the composite material. Continuous fibers exhibit the highest strength when orientated uni-directionally, i.e. where all fibers are aligned in a single direction, as the strength in fiber composites is gained through the fibers and the direction in which those fibers are set.
Uni-directional continuous fibers.
At Oribi we specialize in leveraging uni-directional, continuous fibers composite materials to produce highly optimzied structural parts. We dictate a part’s strength, stiffness and flex by strategically placing the fibers in certain directions within the layup to get the desired mechanical properties within the part. The outcome is a part made with the right materials in the right areas, using fiber only where it is needed to optimize performance and reduce weight.
Engineered ply orientation.
With woven material, the fiber angles are already established, so the ability to customize the fiber angles diminishes greatly which could lead to either a poorly performing part, or excess material used to achieve the necessary results. Most woven fiber products are limited to two perpendicular angles (0° and 90°). Few products require the same amount of fibers running perpendicular to each other; as a result, woven cloth tends to produce heavier products with lower performance, at a much higher cost. The ability to customize the fiber direction enables us to use only as much material and fiber the part requires rather than waste material. This translates into lower material usage, weight, thickness and cost.
For example, if a part requires all its strength from points A to B, all the fibers would be run in that direction and not waste material running fibers in other directions. Woven fiber would only have 50% of it’s material running from A to B simultaneously wasting 50% additional fiber material running from C to D. If Part B requires 70% strength in the A to B direction and 30% strength in the C to D direction, we can place the fibers in exactly the percentages required to keep the material usage low. While woven fiber would waste significantly more material to meet the same mechanical requirements. The enormous advantage of uni-directional fiber is it allows you to customize the fiber direction to the required angles, therefore minimizing waste material, costs, and weight.
On a pure performance basis, there is NOTHING stronger than a uni-directional fiber layup.
Cosmetic surface finish.
Carbon fiber is most commonly identified by the traditional “weave” look of woven cloth. While some consider it an attractive external appearance, composite parts are typically used for higher performance than appearance. As the composites market matures, customers are driving towards high-performance parts and leveraging painting/coatings options for aesthetic concerns. Several coatings/finish options are available for thermoplastic materials for parts that need to have a certain surface quality.
The benefits of thermoplastic composites.
Any thermoplastic composite is tough. The nature of using plastic to bind the fibers together make an extremely tough part. That said, fiberglass is often considered a ‘tougher’ material over carbon fiber because of it’s ability to flex further without breaking. The incredible rigidity of carbon makes it less capable of enduring certain abuses than fiberglass.
In general, uni-directional composite-reinforced thermoplastics have a very low, near zero Coefficient of Thermal Expansion (CTE) than other materials, including epoxy composites. Coefficient of thermal expansion determines the change in material size in relation to a change in temperature. In fact, carbon fiber has a negative CTE which means it will expand slightly when the temperature lowers. This is offset by the positive CTE of the matrix (plastic) which results in a near-neutral CTE for the part.
Carbon fiber composites are 70% lighter than steel, 40% lighter than aluminum, and about 15% lighter than fiberglass composites. The nature of a carbon fiber is very light, rigid, and strong which is why most weight-critical performance products are manufactured with carbon fiber.
Carbon and glass fiber composites both perform very well in acidic or corrosive environments. The matrix (resin) binding the fibers together can enhance this ability to small or very large degrees.
Fiberglass composites are considered insulators and do not pass through the flow of an electric charge. Carbon fiber is conductive, which may help promote surface treatments such as powder coating. Both carbon fiber and fiberglass composites are considered “radio-lucent” which means they are virtually transparent to radio and x-rays.
STRENGTH AND RIGIDITY
Carbon fiber and glass fiber are both very strong and demonstrate high strength-to-weight ratios. Choosing between carbon and glass fibers can often come down to rigidity of the desired part. In applications where a small amount of flexibility is desired, carbon fiber is the material of choice. In applications where a large amount of flexibility is required, fiberglass is better suited to provide a higher ultimate breaking point than the same part in carbon fiber. Fiberglass is better suited to extreme flex patterns, while carbon fiber has a relatively small flex window.
Long strands of carbon fibers are very difficult and expensive to manufacture, while fiberglass processes much easier. As a result, fiberglass is considerably less expensive than carbon fiber.
Some parts require the stiffness of carbon fiber, yet also have aggressive cost targets to satisfy the market. We can often use both carbon and glass fibers within the same part to get the unique qualities of each fiber choice, while adhering to program cost structures.