Research and practice have proved that a 1 mm thick case can meet all relevant industry performance specifications for ultra-thin laptops or tablets.
Consumer electronics products are a dynamic market, and the product iteration cycle is very short. Consumers want faster operating speeds, longer-lasting batteries, more durable performance, and lower cost and weight from their smartphones, smart watches, tablets, and laptops. In order to meet the needs of consumers, suppliers are required to provide lightweight, thin-walled profiles with high aesthetics and design freedom, as well as excellent impact resistance and high rigidity materials-this means quality in this market. They also need cost-effective, highly repeatable processing methods to meet the tens of millions of global production needs every year. These pressures have pushed the market first to light-weight metal housings and frames, and are now pushing them to metal / composite and fully composite solutions.
A feasibility study currently underway involves the use of two thermoplastic composite materials to produce a 1 mm thick laptop / tablet case. Research shows that for the challenging consumer electronics market, hybrid thermoplastic composite design may be a viable solution.
Test Case
Since 2012, a series of investments have been made to develop its own unidirectional (UD) fiber-reinforced thermoplastic composite tape, thereby expanding the company ’s core competitiveness in short fiber injection and long fiber thermoplastic (LFT) materials and allowing Expand into the field of higher performance thermoplastic composites.
Due to the design and manufacturing technology, it has been able to quickly and cost-effectively produce net-shaped, high-quality thermoplastic tape-based composite materials for the true high-volume market, and the team began to look for test cases. This demonstration will be an important marketing tool to prove the design concept of thermoplastic composite laminates, produced from composite tapes over-molded with discontinuous fiber-reinforced composite materials. It is also important for the test team to develop predictive engineering tools for material technology to demonstrate the development of high-speed manufacturing processes in the Netherlands.
The relevant expert explained: "We decided to start with something more complicated but not too complicated. The top cover of a very thin laptop or even a tablet looks like a good starting point. We used a simple The overall geometry of a rectangle, it needs to maintain a high aesthetics and provide a lot of complexity on the B side, including accessory functions. The top cover must be very thin, but still able to meet the challenging deflection requirements common in the industry Of course, we must also deliver very consistent products through complex new manufacturing processes. "The team hopes to eventually convert them into smartphone components.
Since they didn't have actual customer designs, they just created protective covers for the screen, so they used universal geometry. In fact, when they started cutting injection molds for in-house development, they were n’t even sure if they were going to make a tablet or laptop top cover, so the top cover was designed for both products. Davis added: "There are many challenges in preparing composite solutions for mass production. In fact, there are many things happening at the same time-strip development, lamination development and process development-we can't wait for all these things We will start our processing only after it is completed, and this is how we finally designed it. "
After completing the basic design, the team will focus on other details, such as the best gate method, what overlap is required between the laminate insert and the overmolding compound, how to handle the automatic placement in the tool, and how to deal with (two Linear thermal expansion (CLTE or CTE) mismatch between composite materials and how to create parts that are easy to repeat.
Meet challenging requirements
The purpose is to develop a top cover with a thickness of 1 mm, which has a high stiffness and passes all performance and aesthetic requirements-especially the center point deflection test that is regularly applied to the cover of a laptop computer to assess the damage required to the screen below Load. Load / deflection requirements vary by OEM, device, and model, but under 40-120 Newton pressure, deflection usually does not exceed 3-5 mm-this situation simulates when a user stands up with finger or elbow pressure Load when entering the cover.
In many industries, the strategy to pass such tests is to increase the thickness of the profile, but the market places emphasis on thinner designs that can free up more space for batteries and other components without increasing the size or weight of the device. Therefore, the team needed to use different design strategies to prevent screen damage-that is, choose a harder material (inserted through a laminate) and use geometric shapes (for example, reinforced by injection molding). But first, they must specify the materials.
One of the materials, polycarbonate (PC), has been widely used in the manufacture of automotive coverings and other parts due to its excellent aesthetics and high impact strength. The biggest disadvantage of this polymer is its resistance to chemical corrosion and surface scratches, but in most cases, these potential problems can be overcome by the application of coatings, paints, or a combination of both.
The related album pointed out: "Because the ultra-light computer is very thin and the internal packaging space is very small, deflection and mechanical performance become very critical. Although from a cost perspective, we would like to use glass fiber reinforcement, but we must use carbon fiber The required stiffness. Therefore, all strip-based laminates are variants of carbon fiber-reinforced polycarbonate.
A predictive model has been developed to simulate the effect of laminate type and structure (with or without overmolding compound) on the performance of molded parts, and a strong correlation between the predicted and experimental results has been reported. These predictive engineering tools are said to accelerate material development.
Overmolded compounds require different methods. Initially, the strategy was to use longer fiber LFT composites, but for a variety of reasons—including higher aesthetic requirements, part sizes, and casting strategies—short fiber composites can better meet project requirements. Another problem is the type of fiber to be used. Short carbon injection-molded composites are difficult to use, although they have high aesthetics; therefore, for their overmolding materials, they finally considered short glass fiber reinforced materials.
Although all-amorphous PCs are less susceptible to warpage than semi-crystalline polymers, the team is still concerned that the high-strength and anisotropic UD carbon fiber ribbon and the isotropic, discontinuous short glass fiber overmolding grade are lower Difference in CLTE under fiber load. Davis explained: "On such a thin wall, there is almost no room for error, so the nuances of CLT are things that we must carefully consider. This has not even touched all the normal issues that are of concern in injection molding, such as gates. Location, filling pattern, packaging pressure, and braid. "All these factors have been verified by simulation and physical testing.
Once the materials were selected, the engineer performed repeated mold filling, structural analysis, and warpage simulations to evaluate laminate placement, geometry, and material combinations to optimize the stiffness of the load / deflection test, as well as other performance and costs Claim. The team stated that they have developed a comprehensive and accurate composite modeling tool (available to customers and run with common structural and processing specifications) that can quickly model and simulate laminate architecture and overmolding compounds Combination and various processing and selection, as well as the performance of molded parts. These tools are said to be able to achieve a strong correlation between predicted and measured performance and are ideal tools to accelerate the development of customized materials.
Ready for prime time, carbon fiber laptop case
The front of the final laptop / tablet case is made of short glass / polycarbonate-copolymer compound overmolded with carbon fiber reinforced polycarbonate tape laminate, this combination is in a 1 mm thick part Meets all relevant mechanical and aesthetic requirements.
The final demonstration product has a laminated insert made of seven layers of carbon fiber / PC glue
The belt (fiber volume fraction is 55%) is made, then consolidated, trimmed, preformed and trimmed again to the final net shape, and then the THERMOCOMP D452 short glass fiber / PC-copolymer (40% fiber content) A grade optimized for high fluidity and high aesthetics has been widely used in this field) for injection molding. This combination can produce coverings with high stiffness and strength at low mass and low cross-sectional thickness, while containing numerous 3D design details, accessory functions, and good aesthetic design to take full advantage of each material.