Components made of composite materials are stronger and more resilient than mono-component materials of the same weight.
That's why composites are often used in lightweight construction applications.
The automotive industry is the main area of application for fibre-reinforced plastics. Industrial lightweight construction using multi-material designs has only become possible thanks to high-performance adhesives.
Fibre composites are mixed or multiphase materials that essentially consist of two main components: the surrounding matrix (plastic, synthetic resins) and the reinforcing fibres (e.g. glass, carbon, polymers or ceramics).
The fibre bundles are surrounded by the matrix-like an elastically enclosed beam.
The combination of these two components gives this material higher-quality properties than either of the two components involved individually.
Advantage: in principle, fibre composites are more stable than monocomponent materials made of plastics for the same weight.
However, since the fibres transmit the main load in the component, the fibre must be aligned according to the load paths in the component.
Glass fibres are also the most widely used fibre types with a share of over 90 %. Depending on the application, the length of typical reinforcing glass fibres is between 10 and 300 µm. Fibres longer than 1 mm are already considered "long" in the field of plastics processing.
Thermosetting: Phenolic resins, Polyester resins, Epoxy resins, Polyimide resins
Thermoplastics: Polypropylene, Polyamide, Polyphenylsulfide, Polyetheretherketone, Polysulfone, Polyetherimide, Polyphenylsulfone, Polyethersulfone, Polyamideimide
Polyamide 6.6 is widely used as the matrix material with an admixture of 20 to 50 percent by weight of glass fibres.
However, most parts made of fibre-reinforced plastics are produced cost-effectively by injection moulding.
Recent trends and advancements in the manufacturing and cost reduction of composite materials has increased their usage in the transportation, industrial, and many other markets in addition to their traditional use in the aerospace field. Driven by increased government regulations on vehicle emissions, the need for light-weighting, and increased end consumer demand for higher performance products, composite materials and parts are increasingly becoming part of an engineer’s day to day design specification. Composites are used in a wide variety of applications to reduce weight, provide improved environmental resistance, improved aesthetics, greater design options and increased stiffness to weight ratio.
Composites require new methods of bonding or joining (beyond traditional mechanical and thermal methods) to allow for design and performance optimization. Fortunately, advances in structural adhesives (such as epoxies, acrylics, and urethanes) have enabled designers to create products meeting structural integrity requirements without the use of mechanical fasteners, rivets, or welding. Additionally, these structural adhesives work well with multiple substrates including plastics, metals, and composites without sacrificing performance properties.
Even Low Surface Energy (LSE) plastics, such as thermoplastic polyolefin (TPO), polypropylene (PP), and polyethylene (e.g. HDPE), which in the past had to be mechanically attached or heat welded, can now be bonded with speciality structural adhesives.
To join composites or mixed materials, mechanical attachments (such as clips, screws, etc.) can be used with virtually any surface, but they require additional steps to mould or create features for the attachment. This can lead to stress concentrations, which may result in plastic cracking and premature failures. Also, drilling holes into composite materials will result in reduced strength due to the introduction of discontinuities in the matrix and reinforcing fibres. All mechanical attachment methods will result in increased weight and often a poorer aesthetic finish.
Heat and friction welding is a common alternative for certain composites. However, these welding techniques are energy and tooling-intensive and limited in the geometries and substrate combinations that can be addressed. In addition to forming strong bonds, structural adhesives can lower overall costs while increasing the durability of products; and are typically lighter weight than mechanical fasteners. Durability is improved because adhesives distribute stress across the entire bonded area, whereas mechanical fasteners, rivets, and spot welding can create stress concentration leading to weak points across the substrates. Furthermore, the use of adhesives provides a way to seal the entire bonding area while also providing a high strength joint. Another huge consideration and advantage for adhesive bonding is the ease in which it allows different materials to be combined – compared to conventional mechanical methods. For example, structural adhesives prevent galvanic corrosion between dissimilar metals. Finally, the cleaner look of bonded joints versus mechanical fasteners allows for better looking, more efficient product builds without additional finishing work. Thus, adhesive bonding could be the best option for joining the next generation of engineering composites and plastics.
For the joining of lightweight materials, numerous products have been developed, including adhesives by 3M, which are perfectly suited for the efficient filling or joining of fibre composites, multi-material systems and low-energy plastics.
These include, for example:
SUBSTRATE 2 | |||||||
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Metals
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Fiber- Reinforced Epoxy
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Fiber- Reinforced Thermosets
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Thermoplastics
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Other Thermoplastics
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Fiber- Reinforced Nylon |
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SUBSTRATE 1 |
Metals | DP420NS DP125 Gray |
DP420NS DP6310NS |
DP6310NS DP8410NS |
DP8010 Blue | DP8410NS DP6310NS |
DP6310NS |
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FiberReinforced Epoxy | DP420NS DP6310NS 760 |
DP6310NS DP8410NS 760 |
DP8010 Blue | DP8410NS DP6310NS |
DP6310NS | ||
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FiberReinforced Thermosets | DP6310NS DP8410NS 760 |
DP8010 Blue | DP8410NS DP6310NS |
DP6310NS | |||
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Thermoplastics | DP8010 Blue | DP8010 Blue | DP8010 Blue | ||||
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Other Thermoplastics | DP8010 Blue | DP8010 Blue | |||||
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FiberReinforced Nylon | DP6310NS |
One example is the 3M™ Scotch-Weld™ Multi-Material Composite Urethane Adhesive DP6330NS. It is a green, non-sag, two-component urethane paste for bonding a variety of composites, plastics, metals and wood. This flexible adhesive has good energy absorption and fatigue properties for durable bonding of composite parts and multi-material assemblies.
When using a Duo-Pak (DP) size adhesive, rely on 3M dispensing equipment for convenient and accurate metering, mixing and dispensing. Designed specifically for multi-material and composite assemblies, our 3M™ Scotch-Weld™ Multi-Material Composite Urethane Adhesive DP6330NS delivers outstanding strength and performance. This adhesive has excellent elongation and stresses strain properties for durable bonding of composite parts and multi-material assemblies, including plastics, metals and wood. With a 1:1 mix ratio, this green adhesive has a 30-minute open time and reaches handling strength in approximately 2 hours. Adhesive features excellent water and humidity resistance with very good chemical resistance. Recommended Applications Bonding composite or plastic panels to metal frames Bonding composites to each other 3M™ Scotch-Weld™ Multi-Material Composite Urethane Adhesives DP6330NS can replace rivets and screws in attaching composites to other substrates, providing a more aesthetically pleasing, fatigue-resistant bond line. It also bonds well to most metals without requiring priming.
Let's work together! 3M products are constantly evolving to better meet customer needs. If you need help finding the right product for your project or have other questions about 3M solutions: