High-Speed Forming of Continuous Fiber Reinforced Thermoplastics

Abstract

Forming processes of continuous fiber reinforced thermoplastic materials are oftentimes limited to high volume production due to the high costs for tooling and processing machines. This study suggests the combined use of a cold and simple tool and high forming speeds to reduce tooling and processing costs and enable the usage of common stamping machines. Half sphere samples are produced from single and two-layer polypropylene and glass fiber organo-sheets in a custom built drop tower and analyzed for their geometry, degree of re-consolidation, surface quality and potential fiber damage using a variety of microscopy techniques. While only mediocre degrees of reconsolidation and limited surface qualities can be achieved with the combination of a cold tooling and state-of-the-art forming speeds of 0-0.5 ms −1 , the usage of a higher forming speed of 3 ms −1 , vastly improves surface qualities and the degree of reconsolidation without any detectable fiber damage. This effect is more pronounced in the dual layer material. Extensive knowledge on the forming behavior of continuous fiber reinforced thermoplastics at high cooling rates and high speeds of deformation is required for sufficient process control and future studies need to further elaborate and quantify the influencing factors and limits of high-speed forming of continuous fiber reinforced thermoplastics.

Thermo‐mechanical modeling of the temperature dependent forming behavior of thermoplastic prepregs

“…) n(T) + e(T) (12) that was previously used for the mathematical description of flow curves of thermoplastics by Behrens et al 18 Temperature dependent coefficients can be determined using the yield curves provided in Figure 2(C). Thus Equation ( 12) is suitable to identify the yield behavior of the thermoplastic at higher temperatures T < T m , as depicted in Figure 5(B).…”

“…Besides standard test methods like the cantilever test for bending or the picture frame and bias extension tests for shear characterization, Sachs et al 11 and Haanappel et al developed advanced procedures to characterize the bending and membrane behavior respectively. Recently published studies of high‐speed thermoforming processes by Mattner et al 12 suggest forming velocities of more then 1000 mm s. For the resulting deformation rates, the viscous behavior of the examined thermoplastic prepregs can be neglected.…”

“…A layer‐wise modeling approach as presented by Döbrich et al 8 is applied to decouple the bending and membrane behavior. Considering the findings by Mattner et al, 12 punch velocities of about 500 mm s are applied during the thermoforming simulations. These cause local shear rates of more than 1000 °s.…”

Direct In-Mold Impregnation of Glass Fiber Fabric by Polypropylene with Supercritical Nitrogen in Microcellular Injection Molding Process

“…Continuous fiber reinforced thermoplastics polymer composites (CFRTPC), as a typical representative of lightweight materials, have been widely developed and applied in the fields of aerospace, automobile transportation, the chemical industry, electronic appliances, construction, home furnishings, sporting goods, etc. [ 1 , 2 , 3 , 4 ]. CFRTPCs are composed of a thermoplastic resin matrix, continuous fibers, and some additives.…”

Polyimide fabric-reinforced polyimide matrix composites with excellent thermal, mechanical, and dielectric properties

“…Carbon and glass fibers are the most commonly applied fibers in a reinforcer, and the density of the corresponding composites is 1.5-1.9 and 1.8-2.2 g/cm 3 , respectively. [24][25][26][27] With the rapid development of science and technology in the aviation and aerospace fields, the demands for heat-resistant materials with lower densities have become increasingly urgent. For example, the "North Star A-3" submarine missile in the United States uses a fiber-reinforced fiberglass shell, which is approximately 55% lighter than the traditional steel "A-1"…”