Strength is one of the first things people think about when industrial composites are mentioned. Thoughts turn to rigid, lightweight parts designed with enough durability to withstand considerable punishment. And yet, in many high-performance industrial applications, composites need to be flexible to a certain degree.
Achieving the perfect balance of durability and flexibility is not easy. But that balance is a function of the entire composite system. Playing a key role is the epoxy resin matrix that holds everything together.
We like to say that the resin matrix is flexibility’s unsung hero. Bear in mind that composite materials are usually made from two primary components. The first component is a reinforcement like fiberglass or carbon fiber. It provides the strength and stiffness the finished material is known for.
The second component is the matrix resin. Resin binds the reinforcing fibers together. It also transfers load and protects the fibers from the surrounding environment. Here is the thing to understand: while fibers determine a composite material’s ultimate tensile strength, it is the epoxy resin that determines how the material will behave under stress.
More specifically, the resin matrix determines flexural modulus and the material’s ability to withstand impact, dynamic loading, and bending – all without breaking. Optimizing flexibility is really about choosing the right resin matrix.
Given that a material’s resin matrix is the single largest factor in flexibility, it stands to reason that flexibility could be enhanced by manipulating resin matrices. Well, it can. By fine-tuning the chemistry of an epoxy resin, flexibility can be customized. Three things come into play:
Engineers looking to enhance flexibility start with a base epoxy formula. Epoxy resins are synthesized from a variety of chemical building blocks. They can be further enhanced by:
Engineers are fortunate to have access to an almost unlimited number of epoxy combinations. By choosing the right resins and manipulating them, the finished material’s properties can be significantly altered.
The base formula can be further toughened by adding rubber or elastomer particles to the epoxy system. Rubber particles act as a stress concentrator or crack terminator whenever small cracks start to propagate within the matrix.
Meanwhile, elastomer particles absorb fracture energy. They also divert the path of the crack, essentially making the finished material less susceptible to failure because of impact or bending.
Finally, the best base formula and additives are only as good as the curing cycle they are subjected to. Curing needs to be controlled in order to achieve the desired properties. To enhance flexibility, time and temperature need to be specific.
Incomplete curing leads to softer and more flexible composites. But those composites are weaker. Yet a perfectly optimized cure maximizes cross-linking while ensuring that the resin network structure remains intact. Optimizing for a particular stiffness and flexibility balance creates the perfect composite material.
Aerodine engineers have the skills and knowledge to produce composite materials to your exacting specifications. If your industrial composite needs dictate a more flexible material that’s still durable enough to get the job done, we can make it happen. Contact us to discuss how our team can engineer the perfect composite solution for your products.
