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Multifunctional truck cross member made of continuous fiber reinforced plastics

Magna develops and implements new concepts for commercial vehicles to make them lighter, smarter, and more efficient. In the case presented here, the Goal is to replace a component used in truck frames with a new light-weight structure with further functions integrated. A cross member (CM) (Figure 1) composed of continuous carbon fiber-reinforced plastic (CFRP) that combines the standard function of connecting the side rails with a tank for storing compressed liquid gas (CNG) or other fuels was created as a demonstrator.

Figure 1: Demonstrator of combination cross member and CNG tank

Figure 1: Demonstrator of combination cross member and CNG tank

 

Motivation

Passenger vehicles are not alone in having to meet high standards for reducing CO2 emissions and fuel consumption. Commercial vehicles must also meet these requirements, making reducing weight to increase payload and switching to alternative fuels are two goals to strive for.

 

Structure

The composite cross member features the following structure (Figure 2).

  • Liner: The innermost part made of high-density polyethylene (HDPE). Its function is to make the tank airtight. During production the basic contours of the tank liner serve an additional function as the core around which the 90° winding and braiding are performed.
  • 90° Winding: This layer bears the main internal load and is made of carbon fiber-reinforced plastic. For a compressed natural gas (CNG) tank, the operating pressure is 200 bar and the burst pressure is 450 bar.
  • Steel Calotte: A steel spherical cap at both ends that absorbs the operating pressure.
  • Braiding: The longitudinal force generated by the two calottes and the forces generated by the cross member function are absorbed by These CFRP layers.
  • Reinforcement: At both ends of the CM the braiding is reinforced with a steel plate. The reinforcements are positively connected with the braiding using metal pins (T-IGEL® concept from Teufelberger Composite). As for conventional steel cross members, the structure is mounted on the side rails via gussets. During production the basic contours of the reinforcement serve as the core for the braiding process.

 

Figure 2: Cross section through cross member

Figure 2: Cross section of cross member

 

Implementation and Testing

Magna worked closely with ist partner, Teufelberger Composite, during the entire development process. Several demonstrators were produced which showed the feasibility of producing the component and enabled limited basic testing (Figure 3).

maximum torsion moment =          20 kNm
torsions stiffness =                          10 kN/m/degree

This delivered basic feedback for the dimensioning and analysis process of this innovative component. The local fiber orientation in the FE model was improved by evaluating the demonstrator. The torsional and bending stiffness as the maximum torsional moment are used to fine-tune the material data (tensile modulus and strength values). This increases the accuracy and reliability of the analysis as material data in the first analysis loop was based on estimates.

 

Figure 3: Torsion misuse test

Figure 3: Torsion misuse test



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