Processing and Characterization of Continuous Fibre Tapes Co-Moulded with Long Fibre Reinforced Thermoplastics

Abstract

An important advantage when designing with plastics is the ability to incorporate features such as ribs, grids and bosses in the part. Rib stiffened polymer matrix composites have been widely used in aerospace, automobile, and civil infrastructure applications due to their high impact and fatigue resistance, high strength and stiffness to weight ratio, and damage tolerance. However, for long fibre-reinforced polymer composites, the processing complexity increases for features including ribs, grids and bosses. An innovative method of replacing ribs is the use of pre-consolidated continuous fibre reinforced thermoplastic (CFRT) tapes that can be co-moulded with long fibre thermoplastics (LFT). This work focuses on processing and performance evaluation in terms of the static and dynamic properties of LFTs co-moulded with pre-consolidated CFRTs, referred to as endless long fibre thermoplastic (E-LFT). The E-LFT approach is an alternative to rib stiffened composites. The effect of the thickness and fibre type in tape reinforced LFT is compared to LFT (with and without ribs) of equivalent flexural rigidity for static flexure and low velocity impact (LVI) response. In all these conditions, E-LFT samples performed better that the LFTs with and without ribs. LFT samples with and without ribs exhibited a brittle failure, as opposed to the progressive failure exhibited by E-LFT.

A review of Long fibre thermoplastic (LFT) composites

“…Endless LFT (E-LFT) is an example of a common hybridised material. E-LFT combines LFT with unidirectional fibre composite, generally with the same polymer matrix for adequate bonding to enhance its rigidity, strength [290][291][292][293], and/or impact resistance [111,294]. Thattaiparthasarathy et al [291,295] studied the effect of different types of endless fibre composites on the strength of glass/PP LFTs by compression co-moulding the LFT onto the endless fibre composite.…”

“…E-LFT combines LFT with unidirectional fibre composite, generally with the same polymer matrix for adequate bonding to enhance its rigidity, strength [290][291][292][293], and/or impact resistance [111,294]. Thattaiparthasarathy et al [291,295] studied the effect of different types of endless fibre composites on the strength of glass/PP LFTs by compression co-moulding the LFT onto the endless fibre composite. The average flexural strength for endless E-glass, S2-glass, and carbon fibre E-LFTs were 137.4, 163.9, and 180.6 MPa, respectively, compared to an average of 106.5 MPa for glass/PP LFTs without any unidirectional fibre composite.…”

“…The average flexural strength for endless E-glass, S2-glass, and carbon fibre E-LFTs were 137.4, 163.9, and 180.6 MPa, respectively, compared to an average of 106.5 MPa for glass/PP LFTs without any unidirectional fibre composite. Figure 12 shows a glass/PP LFT plate co-moulded with unidirectional glass fibre PP tapes [291]. In another study, a carbon/ PA6 LFT was hybridised with a continuous fibre composite using injection moulding.…”

“…Desirable properties at certain locations of an automotive component can also be readily achieved by strategical placement of the continuous fibre in the composite. It is expected that these advantages will enable continuously increasing use of the continuous fibre hybridised LFT composite in automotive and other applications.

Figure 12.Co-moulded unidirectional/endless glass fibre PP composite with glass/PP LFT [291].

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Materials for Automotive Lightweighting

“…IOM is being used more extensively in automotive components such as door inners, bumper beams, instrument panels, and crash members. In IOM, a thin layer of continuous fabric preforms or tapes provides the structural load-bearing elements, and complex features such as ribs, bosses, and steps are back molded with a high-performance polymer and/or LFT such as glass or carbon polyamide 6 (PA6-C) (110)(111)(112). The advantage of this approach is the ability to achieve highly complex, near-net shapes in cycle times of less than 90 s. Figure 23 illustrates the cycle of a part produced with this process (110).…”