Fabrication of Micro-Groove on the Surface of CFRP to Enhance the Connection Strength of Composite Part

Carbon fiber-reinforced plastic (CFRP) has the advantages of being light weight, high strength, and corrosion resistant. At present, it is widely used in the lightweight design of automobile parts. The manufacturing of lightweight parts inevitably involves the connection between CFRP and the polymer material. The connection strength between CFRP and the polymer material significantly affects the service life of the composite parts. Taking CFRP and polyamide 6 (PA6) injection-molded composite parts as an example, this paper proposed a technological method to enhance the connection strength between CFRP and PA6. The proposed method was to fabricate micro-groove structures on the CFRP surface by compression molding. These micro-groove structures effectively increased the injection-molding area of the composite parts, thus enhancing the connection strength between CFRP and PA6. This paper presented a detailed study on the compression-molding process of micro-grooves on the CFRP surface, and successfully obtained the appropriate parameters. Finally, PA6 was used for injection molding on the CFRP with micro-grooves at an injection pressure of 8 MPa, an injection temperature of 240 °C, a holding pressure of 5 MPa, and a holding time of 2.5 s. The experimental results show that the micro-groove array structures on the CFRP surface could effectively improve the tensile strength of the connection interface in the composite parts. Compared with the composite part without micro-grooves, the tensile strength of the composite part with micro-grooves was increased by 80.93%. The composite parts prepared in this paper are mainly used in automobile interiors and the research results of this paper meet the actual needs of the enterprise.

A thermoplastic resin matrix and its physical properties suitable for deformable mandrel

The mandrel is able to shape the part cavity, therefore is of great significance for composite parts in the manufacturing of carbon fiber reinforced polymer(CFRP) composite part. However, in the manufacturing of composite parts with complex cavities, traditional rigid mandrel cannot be removed out of the cavity in any direction after the outer prepreg is cured. To solve the problem of difficult demolding, a kind of deformable mandrel emerged. The deformable mandrel is rigid at room temperature to support composite part curing. While at relatively high temperatures, the mandrel is softened so that the mandrel can be easily removed from the composite part despite the complex part cavity shape, therefore resolving complications regarding the demolding process. In this paper, a thermoplastic resin material matrix suitable for the preparation of deformable mandrel is proposed. Ingredient and manufacturing flow of the thermoplastic resin matrix are introduced, and the applicability of the proposed matrix with regard to the deformable mandrel is validated through dynamic mechanical analysis.

Draping modelization of stitched composite reinforcements

In the aeronautic industry, thicker and more complex composite parts are required. Multi-layered reinforcements are widely used to achieve a certain thickness for the composite part. The tufting technology has become one of the most effective three-dimensional (3D) reinforcement technologies to improve the through-the-thickness mechanical properties of multi-layered reinforcements. A finite element model is proposed for the simulation of tufted reinforcements preforming. The textile reinforcement is modelled by shell elements, and the tufting thread is modelled by bar elements. A specific contact algorithm is developed to manage the interaction between reinforcements and tufting threads. This meso-macroscopic approach reduces the number of finite elements and saves calculation time compared to a mesoscopic model. The model shows a good prediction of deformations during the forming on a hemispherical shape.

Assessment of Replacement of Metal Parts by BFRP Composites into a Highly Efficient Electrical Prototype

This work intends to evaluate the use of epoxy composite materials reinforced with basalt fibers as replacement to metallic mechanical parts of a highly efficient electrical prototype. The analysis of the behavior of the original metallic bracket was made and an optimization process was carried out in order to achieve the most suitable geometry and stacking sequence if produced in composite material. Finite element analysis using Siemens NX12 and experimental tests to the produced composite part were performed in order to access it. It was verified that the total weight of the composite part shows a 45% reduction. The composite part shows a higher deformation than the metallic one due to basalt fiber’s higher flexibility. However, the advantages added by the new component largely compensate for the disadvantages that may have been added without compromising its performance. Obtained results show that the use of basalt fiber reinforced composites as the material of mechanical parts of a highly efficient electrical prototype that is a good alternative.

Processing and mechanical behavior of rigid and flexible material composite systems formed via voxel digital design in polyjet additive manufacturing

Purpose PolyJet technology allows printing complex multi-material composite configurations using Voxel digital designs' capability, thus allowing rapid prototyping of 3D printed structural parts. This paper aims to investigate the processing and mechanical characteristics of composite material configurations formed from soft and hard materials with different distributions and sizes via voxel digital print design. Design/methodology/approach Voxels are extruded representations of pixels and represent different material information similar to each pixel representing colors in digital images. Each geometric region of a digitally designed part represented by a voxel can be printed with a different material. Multi-material composite part configurations were formed and rapidly prototyped using a PolyJet printer Stratasys J750. A design of experiments composite part configuration of a soft material (Tango Plus) within a hard material matrix (Vero Black) was studied. Composite structures with different hard and soft material distributions, but at the same volume fractions of hard and soft materials, were rapidly prototyped via PolyJet printing through developed Voxel digital printing designs. The tensile behavior of these formed composite material configurations was studied. Findings Processing and mechanical behavior characteristics depend on materials in different regions and their distributions. Tensile characterization obtained the fracture energy, tensile strength, modulus and failure strength of different hard-soft composite systems. Mechanical properties and behavior of all different composite material systems are compared. Practical implications Tensile characteristics correlate to digital voxel designs that play a critical role in additive manufacturing, in addition to the formed material composition and distributions. Originality/value Results clearly indicate that multi-material composite systems with various tensile mechanical properties could be created using voxel printing by engineering the design of material distributions, and sizes. The important parameters such as inclusion size and distribution can easily be controlled within all slices via voxel digital designs in PolyJet printing. Therefore, engineers and designers can manipulate entire morphology and material at each voxel level, and different prototype morphologies can be created with the same voxel digital design. In addition, difficulties from AM process with voxel printing for such material designs is addressed, and effective digital solutions were used for successful prototypes. Some of these difficulties are extra support material or printing the part with different dimension than it designed to achieve the final part dimension fidelity. Present work addressed and resolved such issued and provided cyber based software solutions using CAD and voxel discretization. All these increase broad adaptability of PolyJet AM in industry for prototyping and end-use.

Anticipation of damage presence in a fibre reinforced polymer plate through damping behaviour

Failure of composite materials due to poor anticipations of damages occur very frequently. Damages in composite materials may exist as visible or non-visible with different configurations and identities. Thus, investigation of damages existence in composite materials has to have prior attention to avoid the failure of structures. The current work investigates the damping response offered by a damaged fiber-reinforced polymer plate. The plate is put under three different conditions regarding the damage existence. The focus is to measure the loss factor in all cases and determine whether there is a difference among them to prove damage presence in the composite part. The loss factor is experimentally measured by measuring the reverberation time RT60. The resulting data of loss factors show a well-distinguished difference that might lead to predicted damages and to do a more expanded analysis of this issue.