In recent years, continuous fiber reinforced thermoplastic materials (CFRTP and GFRTP) have become very attractive in the automotive industry as one of the lightweight and high-strength solutions such as HV (hybrid), PHV (hybrid when inserted), EV (electric vehicle), and FCVS (hydrogen energy fuel cell vehicle). One of the main reasons is that continuous fiber thermoplastic resins have different molding cycles than thermosetting resins CFRP and GFRP, which can be rapidly formed in 60 seconds. As reinforcement fiber, not short fiber or long fiber, but the use of carbon or glass continuous fiber, and the longer the fiber length, the more can achieve high strength, high rigidity requirements.

01

Continuous fiber thermoplastic material

The so-called continuous fiber thermoplastic material refers to the continuous fiber is completely impregnated in the thermoplastic resin after the intermediate material, usually in the form of sheet (flat), does not need to be like thermosetting resin, the need for the operator in the dust-free workshop layer by layer, but as shown in Figure 1, with the required thickness of the sheet, and can be stored at room temperature.

Width: 620mm, 860mm, 1250mm

Length: any

Sheet thickness: 0.25~6.0mm (using different resins, the maximum thickness of the sheet is different)

In addition to the above materials, there are also PC (polycarbonate) flame retardant (UL94V-0) materials. The layering method can be customized according to the requirements.

02

Methods for making continuous fiber thermoplastic materials

Continuous fiber thermoplastic sheet can be manufactured by belt continuous composite press as shown in Figure 3. The rolled carbon wire or glass wire is heated, pressurized, impregnated with plastic resin, and cut into the required size after cooling, according to the required number of paving layers.

With a density of 1.45, carbon fiber is lighter than fiberglass (1.8), and on all measures, carbon fiber outperforms fiberglass. However, compared with the price of glass fiber 100, the price of carbon fiber is 1000~2000, so in the design of products to use which material is more appropriate, we need to consider the balance between the proportion of 0.35 difference and the price, according to the use of the best material.

04

molding

Stamping forming of continuous fiber plastic materials. When the continuous fiber thermoplastic material is preheated to the forming temperature, the hard sheet (plate) becomes as soft as a wet towel. At this time, a certain pressure can be applied to complete the 3D molding. In general, the pressure required by each molding method is as follows:

Diaphragm forming (hollow forming) : 3~5bars

Stamping forming: 5~10bars

Compression molding: more than 100bars

The key to shaping is to control the flow of fibres in resin, which, unlike metals, do not extend.

05

Hybrid molding

At the K-show in Dusseldorf, Germany in 2010, Krauss Maffei and Engel shocked visitors with a 60-second demonstration of hybrid molding using continuous fiber thermoplastic materials. In the K-show of 2013, apart from the two companies mentioned above, Arburg Company conducted four demonstrations by three companies in total. Hybrid molding involves 3D bending a continuous fiber thermoplastic material using a single mold through an injection molding device, completing all operations, including punching holes, in 60 seconds and eliminating the need for subsequent processing to create a finished product. Using hybrid molding can reduce the number of parts. The material cost is higher than iron, but GFRTP is cheaper than iron and can achieve the goal of 50% lightweight. In order to achieve mass production, mixed molding plays an important role. From a few years ago, car parts sourced from Germany were all mixed and formed products. Continuous fiber as reinforcement fiber, mechanical strength is better than short fiber and long fiber, but short fiber and long fiber is easier to form.

The technology has already been used in sports goods, automobiles, communication equipment, and aircraft, and is expected to be widely used in the automotive sector. The hybrid molding technology of continuous fiber thermoplastic material is concerned all over the world, which is not only in Europe and America, but also in Asian countries.

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