With mounting pressure to reduce the manufacturing cycle time, innovative thermoplastic composite materials are rapidly gaining acceptance in both the automotive and aerospace businesses. However, the nonuniform nature of composite materials is not good for laser additive manufacturing.
Polymer composites, by their nature, are made with at least two constituent parts. The matrix include at least one reinforcement material and another to support the reinforcement material. For instance, one layer maybe carbon fiber-reinforced polymer; another layer, epoxy. The mismatch between the conductivity of carbon fiber-reinforced polymer and epoxy makes traditional laser cutting almost impossible. Epoxies are a type of thermoset polymer.
Because each material has its own unique physical attributes, and because these materials are highly anisotropic, laser processing is extremely problematic. Conventional lasers are ineffective for polymer composites. Although it is challenging for the laser manufacturing industry, the following solutions are transforming the industry.
Polymer Composite Solutions
1. Hybrid Lasers
Carbon fiber can be cut with either CO2 lasers or fiber lasers, but the best cut is achieved when combining a 10.6um laser beam (using CO2) and a 1.06 um laser beam (using fiber) into a single hybrid laser beam. The 1.06 micron laser is used to cut the carbon fiber, while the 10.6 micron beam removes the thermoplastic material. Using lasers for cutting CFRP material is better than mechanical cutting because edge damage is reduced.
2. Using Lasers to Strengthen the Adhesive Bond
The auto and aerospace industries also use lasers to improve adhesive bond strength. For example, instead of using chemicals, abrasives, or blast media, lasers are now used to clean and prepare composite surfaces before bonding. Laser processing is superior because it is non-contact in nature and is highly precise.
3. Localized Repair
Working with composites often involves localized damage. Unlike manual grinding, for example, laser processing do not apply force or vibration to the structure. Damage can therefore be better repaired with a controlled, repeatable laser ablation process and injections of compatible thermosetting resin.
4 Laser Welding
Since the properties of composite substance are so dinstinct, combining composite materials is different from combining metals. For instance, riveting weakens or damages the composite material. Laser welding is possible only when one constituent part is thermoplastic and another transmit radiation. If the carbon fiber part is a thermoset, it must be ablated until the fiber structure is exposed. The open fiber structure improves structural strength and reduces laser absorption. Keep the welding temperature constant with a pyrometer to improve weld quality.