Carbon fiber-reinforced thermoplastics offer the possibility for short lead times and dustless assembly in aerospace applications. However, their great potential for efficient processing to date is not entirely exploited. At the Center for Lightweight Production Technology (ZLP) in Augsburg smart automation of thermoplastic composite production is investigated. To assess the overall process chain a sine wave beam designed as crash-absorber serves as demonstrator. The production process from as-delivered material to final assembly is presented. In addition to non-destructive testing at the end of the value adding process chain, production-integration quality assurance, and process characterization serve to evaluate each process step. In this context, water-coupled ultrasonic testing as an established method in aerospace production is used to assess the degree of consolidation after vacuum consolidation and press-forming. Thus, quality issues and crucial process parameters can be identified and optimized to improve robustness.

Ring filament winding enables processing of continuous fibers for manufacturing unidirectional non-crimp unidirectional preform plies on straight-, curved-, or closed-mandrel geometries. However, unidirectional processing of tows can lead to increased lateral tow slippage. The objective of the present study is thus to validate unidirectional winding methods for ring filament winding, performing geodesic and non-geodesic trajectories analytically and experimentally. Implementation of geodesic paths investigates the influence of the tensile force and take-up velocity on the winding angle reproducibility. Non-geodesic winding paths are conducted here dependent on winding methods, slippage coefficients, and the mandrel’s surface materials, evidencing the occurrence of lateral tow slippage by measurements of nip-point forces. Findings indicate an excellent reproducibility of geodesic paths independent of the process velocity. Non-geodesic paths were partially validated because of the occurrence of lateral tape-slippage and a tape side-inclination effect, correlating an increased stick behavior to higher local normal pressure.

Continuous ultrasonic welding of plastic films, fabrics, and even thermoplastic composite prepreg tape is a common industrial practice. However, continuous ultrasonic welding of stiff thermoplastic composite plates is challenging due to squeeze flow of resin at the welding interface, and significant local deformation of the welding stack, that are generally needed to achieve strong welds. This paper presents a novel approach to continuous ultrasonic welding of thermoplastic composite plates based on zero-flow welding. The proposed technique can create strong welds before any squeeze flow takes place at the interface. It is enabled by the use of very thin flat energy directors, owing to simultaneous melting of both energy director and adherends’ matrix. The results prove the feasibility and indicate the potential for high-strength welds between thermoplastic composite plates at very high speed.

A novel method for dry alignment of discontinuous carbon fibers, such as recycled carbon fibers was developed by the modification of the yarn manufacturing process. In order to achieve high production rate and application for long fibers, fluffy synthetic fibers were used as the suspending and carrying media for discontinuous carbon fibers instead of a fluid medium generally used. Using the mechanical interaction in the dry alignment method, a mixture of 200 mm long discontinuous carbon fibers and fluffy polypropylene fibers was fabricated into an aligned and homogeneously comingled sliver by drafting. Then, the sliver was spun into yarn and an aligned yarn preform was obtained. Composites, with approximately 70% of the fibers aligned within an angle of ±14° with respect to the drafting direction, were successfully produced from the preform of the aligned spun yarn. The tensile modulus of the composite specimen along the aligned direction was about 10 times larger than that along the transverse direction, and about 3.5 times larger than that for the specimens obtained from the same yarn with random orientation.

Thermoplastic matrix polymer composites have gained commercial success in the semistructural and structural applications. Polyethylene (PE) is one of the most versatile and widely used thermoplastics in the world because of its excellent properties like toughness, near-zero moisture absorption, excellent chemical inertness, low coefficient of friction, ease of processing and unusual electrical properties. This review is designed for comprehensive source of PE-based polymer composites research, including structure and classification of PE manufacturing/processing techniques for PE composites, and it also described different characterization methods for PE composites. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) characterization methods were used to describe the thermal properties of PE composites. Morphological studies were explained by using scanning electron microscope (SEM), transmission electron microscope (TEM) and atomic force microscope (AFM) techniques. Rheological properties and dynamic mechanical analysis (DMA) are also discussed in this review. X-ray diffraction (XRD) characterization was described in this review to explain crystallinity in PE composites. Hence, this review offers a comprehensive discussion on processing and characterization of PE-based composites.

This paper presents a study of the cure of carbon fiber composites by the direct application of an electric current. The conductivity of carbon fiber enables the individual fibers to act as heating elements. The result is a large number of heating elements throughout the composite structure. These heating elements locally heat the resin surrounding them, resulting in the resin curing. This study shows that cure of composites is achieved in samples up to 60 × 25 cm. Initially, the required contact arrangement to obtain a uniformly heated panel is assessed and an optimum arrangement achieved. Following this, the change in required energy as the sample thickness and sample length are changed is measured. The degree of cure is compared to conventionally cured composites using differential scanning calorimetry (DSC). Three-point bend testing is used to determine the flexural strength and modulus of the composite samples. The results show that a comparable level of cure can be obtained using direct application of an electrical current as that obtained using autoclave cure and oven cure processes.

Advanced composites are used extensively in many high performance applications. As they are taken up in a wider range of applications, the volume of demand is pushing manufacturing methods, especially hand layup of woven prepreg cloth, to their limits. An alternative approach to hand layup over complex geometries is proposed. The regular method of layup involves generating shear using grasps and pressures in the prepreg as and when it is needed during layup, leading to a sometimes complex and time consuming process. In the method proposed, all the shear deformation is created in the ply prior to any contact between the prepreg and the mold surface. Guidelines were drawn onto the prepreg surface to enable the correct shear distribution to be ‘presheared’ by hand. These were created by processing the outputs from a simple kinematic drape simulation within MATLAB. Once preshearing was completed, the ply is laid up onto the mold using regular hand layup techniques. The process was tested alongside regular manual lamination across three example parts and using video analysis effects of the process were investigated via a variety of metrics. This revealed that significant time savings and reduced likelihood of manufacturing variations are possible with this approach. There was also a significant simplification of the layup process, leading participants to comment that a previously ‘difficult’ layup had become ‘easy’. An improved bespoke system for communicating the required preshearing was subsequently developed, and successfully trialed on a fourth example part. Preshearing has the potential to make hand layup more economically viable for years to come. As well as the productivity and cost benefits, preshearing shows promise as a training aid, especially for beginner laminators. Concepts for integrating preshearing into existing industrial practice and its further potential in the field of automation are also discussed.