Papers by Keyword: Thermoplastic

Abstract: Thermoplastic-based sheets (TBSs) are increasingly adopted in the automotive and aerospace sectors due to their potential for producing lightweight and durable structures. However, conventional manufacturing techniques, such as compression molding, offer limited process flexibility, as they rely on costly, dedicated molds. Single Point Incremental Forming (SPIF) represents a promising die-less alternative. Nevertheless, its application to thermoplastics requires strict control of the process conditions to avoid material failure. This study focuses on the validation of a novel experimental apparatus for pressure-assisted hot SPIF. The developed equipment enables precise, real-time control and regulation of both the working temperature and the hydrostatic support pressure, which are critical parameters for enhancing polymer formability. A key aspect of the experimental procedure is the use of an aluminum sacrificial sheet placed between the forming tool and the polymeric blank. This intermediate layer fulfills a dual role by ensuring a hermetic hydraulic seal to prevent fluid leakage and by promoting uniform pressure distribution during the forming process. The experimental results demonstrate the effectiveness of the proposed setup, achieving successful deformation of TBSs with high geometric accuracy. Overall, this research confirms the feasibility and robustness of the designed equipment for processing unconventional materials, offering a flexible and efficient alternative to traditional rigid tooling technologies.

Abstract: Carbon fiber reinforced thermoplastic (CFRTP), such as carbon fiber reinforced polyetheretherketone (CF/PEEK), are applied in aerospace structures because of their high specific strength and recyclability. In this study, cutting tests were conducted to investigate cutting force in drilling of CF/PEEK composites. The lower cutting force was measured at the higher spindle speed. Temperature distributions on the exit side of the hole were compared between two spindle speeds, the temperature at high spindle speed indicates a higher value. The different conditions on machined hole walls were observed between the two spindle speeds. Then, an energy based force model was applied to analyze the thrust and torque during drilling, in which the cutting edge was discretized, and the chip flow was determined to minimize cutting energy. Based on the predicted shear and friction works, a finite difference thermal analysis was performed to evaluate temperature distributions in the tool, chip, and workpiece. The analysis indicated that higher spindle speed leads to an increase in cutting temperature. The results suggest that temperature-dependent behavior of the thermoplastic matrix may influence the shear stress on the shear plane and thereby contribute to the reduction in cutting force at the higher spindle speed.

Abstract: Thermoforming of thermoplastic fiber-reinforced composites enables cost-effective production of complex, high-volume components, yet wrinkling and shear-induced thickness variations remain persistent challenges in compound-curvature geometries, often leading to nonuniform consolidation. This work presents a predictive virtual process simulation that integrates discrete mesoscopic finite element modeling with targeted blank design strategies to address these limitations. The approach, developed by the Sherwood Group and implemented in LS-DYNA, is applied to the thermoforming of a UHMWPE unidirectional cross-ply composite system (DSM® Dyneema® HB210). A thickness-stretch shell formulation (SHELL ELFORM25), coupled with a user-defined material model, is employed to simultaneously capture in-plane shear, through-thickness deformation, and frictional interactions during forming. A parametric study is conducted to evaluate the combined effects of tooling geometry and strategically introduced slits in the blank, including side-and corner-oriented configurations. The results demonstrate that the proposed formulation provides an effective balance between computational efficiency and predictive accuracy while explicitly reducing shear-induced thickening. Notably, corner-oriented slits at 45° to the fiber directions significantly reduced thickness variability and wrinkle severity compared to unmodified blanks and side-slit configurations. These findings highlight the novelty of integrating thickness-aware forming simulations with geometric blank modification as a robust pathway for achieving near-uniform thickness and improved preform quality in thermoformed composite parts.

Abstract: High-performance thermoplastic polymers paved the way for new fast manufacturing pro-cesses, including welding. In order to obtain optimal bonding of the substrates, an adhesion step isrequired, governed by two main phenomena : intimate contact and healing. While healing has beenvastly explored, theorized and starts to be understood, prediction and characterization of the degree ofintimate contact is still a challenge. After a review of squeeze flow models for intimate contact, alongwith the expressions of the analytical solutions for a Newtonian and a shear-thinning fluid modeled bypower law, a finite element model is presented in order to observe the influence of asperity geometry,fluid behavior, and other assumptions on the evolution of the degree of intimate contact.

Abstract: The shift towards electric mobility needs extensive research into battery modules, particularly in relation to safety due to the high energy density of Li-ion batteries. Battery casings must be able to protect the module from external impacts while also containing any potential danger in the event of internal failure. This study presents a comprehensive qualitative screening of thermoset and thermoplastic carbon fiber-reinforced polymers (FRP) used in automotive and aerospace applications under thermal runaway (TR) conditions, to identify suitable materials for battery enclosures. The test setup is an adaptation of the UL 2596 standard with a hexagonal array of seven 21700-format cells. The results indicate that CF-PEEK, CF-PPS, and an aerospace-grade epoxy, CF-EP_str (primary structural material) effectively contain the TR with low damage using the current setup. Medium damage was observed in CF-PC, CF-bio-based phenolic, while non-structural CF-epoxy and CF-PA6 failed to contain the TR. This qualitative study serves as an initial screening process to narrow down materials for further in-depth analysis, emphasizing the need for reproducible TR events for accurate assessment.

Abstract: In order to develop sustainable materials for a variety of industries, hybrid polymer composites reinforced with natural fibers are emerging as a critical option. The various forms of hybrid composites and the employment of various polymers—such as thermoplastics, thermosets, and elastomers—when paired with natural fibers are the main topics of this narrative theoretical review. The article examines the applications of various composites in industries such consumer products, construction, automotive, and aerospace, providing insights into how polymer choice affects a composite's applicability for a given application. Through an examination of recent advancements in hybrid composite design and polymer utilization, this analysis offers a thorough grasp of the present trends and potential applications of these materials in promoting sustainable engineering practices.

Abstract: This study examines the feasibility of utilizing the press forming method on multi-layer, multi-orientation continuous CFRP preform produced by the additive manufacturing (AM) technique. The 5-layer preforms with fiber orientations of 45° and -45° impregnated in Nylon-6 resin layers were made by a 3D printer, and press-formed in varying temperatures and pressures. Optimal forming outcomes were determined by qualitative evaluations of the surface finish, fiber impregnation, resin flow, and quantitative observations on shape variations by comparison with the mold dimensions. Experimental results showed that the molding temperature of 220°C and pressure between 0.5MPa - 1MPa could produce preforms with optimal surface conditions. There was almost no void of bubble defects, no excess resin flow, and a smooth transition was established between the carbon fiber and the matrix resin layers while allowing the full mechanical strength properties to be realized. The formed preform evaluations confirmed that the press molding method is feasible on multi-layer, multi-orientation continuous CFRP with optimal surface conditions.

Abstract: 3D printing has been on the rise in recent times and the civil engineering industry has adopted this technology due to its various advantages. However, printing is largely restricted to concrete members while the reinforcement is introduced manually. The current work looks at the possibility of using 3D printed thermoplastics as formwork and reinforcement for concrete beams. Three different polymeric materials, namely PETG, PLA, and TPU were utilized in this research to fabricate formwork-like reinforcement for 150×150×500 mm concrete beams. The reinforcements were 3D-printed using a fused deposition modelling (FDM) printer in the shape of a formwork to serve as moulds and external reinforcement. The reinforcing formwork geometry was designed with trapezoidal corrugations to ensure strong bonding with the concrete. The beams were tested in four-point bending configuration, and their flexural behaviour was characterized and compared with plain and steel reinforced concrete (RC) reference beams. Results indicate that all 3D printed beams reached a load capacity of around 30 kN. The post-peak behaviour of these beams was dependent on the type of polymer used. The PLA and TPU reinforced beams exhibit large post-peak deflection however their load carrying capacity was compromised, while the PETG exhibited a strain hardening behaviour but with much lower deflections. Overall, the results indicate that 3D-printed thermoplastics are a promising economical alternative to the conventional steel reinforcement.

Abstract: Polyoxymethylene (POM) is a semi-crystalline engineering thermoplastic polymer employed in the manufacturing of precision parts for engineering applications requiring high dimensional stability and good frictional resistance properties. Due to its lower cost and ease of integration into automated manufacturing processes, laser marking is the state of art method vastly employed for marking products aiming to enhance traceability and accountability. Laser marking of polymers can be challenging depending on the outcome of interactions between the material and the laser radiation for a specific wavelength. Low absorption for a wide wavelength range is usual on transparent and white thermoplastics, which is also the case for natural POM. In this work, in a bid to determine the range of feasible process parameters that ensure good-quality markings, which are necessary to developing a lean manufacturing-focused laser marking process, both natural and pigmented POM were laser-marked, and the quality of the substrates and markings were analyzed using a variety of analytical methods. Results indicated a marked difference in the laser mark-ability of natural and pigmented POM, which is attributed to marked differences in laser absorption abilities of natural and pigmented POM.

Abstract: Achieving a strong bond between carbon fiber (CF) and recyclable thermoplastic polymer (TP) has always been highly sought after. So far, applying electron beam (EB) irradiation with optimal dose and cathode potential (V_c) has shown success in increasing mechanical properties of interlayered CFRTPs. However, with concern for durability and safety, higher strength is desired. Therefore, EB setting applying electron beam (EB) irradiation with cathode potential (V_c) to 170, 210, 225 or 250 kV was applied to CFRTPA (carbon fiber reinforced thermoplastic polyamide) articles just before shipping. Specimens were 9 CF plies alternating between 10 PA (polyamide) sheets, designated [TPA]₁₀[CF]₉. When optimal EB dose of 43.2 kGy is applied to both finished specimen surfaces after fabrication, experimental results show higher V_c setting of 250 kV can increase impact strength of the [TPA]₁₀[CF]₉ over that at 170 kV. In summary, the 250 kV-EB (250 kV) strengthens [TPA]₁₀[CF]₉ significantly, about 25 to 27% larger than that of 170 kV and zero (untreated). Based on Christenhusz and Reimer equation to calculate penetration depth, D_th of EBI into polymers, increasing V_c to 250 kV increased D_th to more than 2 times that at 170 kV.