Long-Fibre Reinforced Thermoplastics (LFT)

Long-Fibre Reinforced Thermoplastics (LFT) are a class of high-performance lightweight materials compounded from reinforcing fibres (typically glass fibres) exceeding 10 mm in length and thermoplastic resins such as polypropylene (PP) and polyamide (PA6). Compared to short-fibre reinforced plastics with fibre lengths of only around 1 mm, the intertwined internal fibre network of LFT delivers significantly higher strength, rigidity, and impact toughness, making it a key material for "steel-to-plastic" lightweighting across the automotive industry.

Core Advantages: Balancing Lightness and Strength

The growing prominence of LFT in automotive lightweighting stems primarily from its exceptional material characteristics. Firstly, its low density (approximately 1.2–1.5 g/cm³) enables a 20% to 50% weight reduction when replacing conventional metal stampings. Secondly, the long fibres interlock into a three-dimensional network structure, retaining outstanding creep resistance even under elevated temperatures, with dimensional stability far surpassing short-glass-fibre plastics. Furthermore, LFT offers key manufacturing benefits such as high design freedom, multi-part integration, and lower tooling costs, which help streamline modular vehicle assembly.

Two Main Manufacturing Routes: LFT-D and LFT-G

LFT materials are broadly categorised into two processing routes based on production methods:

LFT-D (Direct Compounding): Resins, roving fibres, and additives are compounded and melted directly in an extruder and fed straight into compression or injection moulds without going through an intermediate pelletising stage. By skipping pelletising, cooling, and re-transportation, this process reduces energy consumption by up to 30% while preserving fibre length for superior mechanical performance. Research from Germany's Fraunhofer Institute indicates that LFT-D can economically produce bespoke composite parts with fibre loadings of 20% to 60%. In China, suppliers such as Guangdong Yatai have commercialised large-scale LFT-D mass production, supplying major carmakers including GAC AION.

LFT-G (Granule/Pellet Method): Fibres and resins are first pre-compounded into long-fibre reinforced pellets (typically 10–25 mm in fibre length) before being moulded using conventional injection machines. While this approach has lower capital equipment barriers, the fibres undergo some mechanical degradation during the secondary melting cycle.

Frontier Applications: Hybrid Moulding and Localised Reinforcement

To fully exploit the mechanical potential of LFT, the industry is advancing cutting-edge processing techniques:

Steel-LFT Hybrid Moulding: Sheet metal stamping and LFT compression moulding are carried out concurrently in a single tool, bonding the materials into a rigid, one-shot metal-composite hybrid structural component. This technique can deliver around a 20% weight reduction on chassis components like lower control arms.

Continuous Fibre-Reinforced LFT: Using glass-fibre LFT as the base matrix, high-strength continuous carbon-fibre-reinforced thermoplastic tapes are applied onto high-stress zones via Automated Tape Placement (ATP). This boosts local tensile strength by 129% and flexural strength by 192%, achieving precise structural reinforcement.

Typical Automotive Applications

LFT is widely utilised across automotive structural and semi-structural components. Key applications include front-end modules (which can consolidate over 10 individual metal parts to shed 30%–40% in weight), instrument panel/dashboard carriers, EV battery pack enclosures (such as the all-thermoplastic battery tray co-developed by Envalior and Kautex with 45% fibre content), underbody aerodynamic shields, door carrier modules, and seat structures.

Future Industry Trends

LFT technology continues to progress towards higher functional integration and lower production costs. In-line compounding injection moulding combines extrusion and injection into a single continuous setup, saving roughly RM3.50 per kg in raw material costs. Meanwhile, hybridising LFT with processes like Glass Mat Thermoplastics (GMT) provides an increasingly viable lightweighting solution for large structural components in new energy vehicles.

Editor's Note: As an advanced structural lightweight material, LFT is typically integrated inside assemblies and not visible to car buyers at a glance. Its real-world value translates into overall kerb weight reduction, improved energy efficiency/range, and crashworthiness. Checking comprehensive crash safety scores from established bodies such as C-NCAP provides an objective benchmark of a vehicle's overall structural integrity.