H-E-A-Tx Composites
COMPOSITES INDUSTRY
Precise thermoregulation in the composites industry that combines multiple materials is critical as the differences in their physical properties such as coefficients of thermal expansion, tenacity, modulus of elasticity, hardness, curing times, etc, varies widely depending on temperature. The sophisticated laminar structures and their reliance upon new and complex temperature sensitive and heat dependent resins means that H-E-A-Tx textiles and composites offer the industry a huge opportunity. The precise thermoregulation is a curing aid and can be used as a “Thermal Trigger” for initiating the curing process of the composite. E-Tx Sensory textiles enable a wide range of conditions to be monitored including; thermal, pressure, stress & strain, moisture, break, fatigue, etc. capabilities can be near-invisibly incorporated into textiles without significantly increasing their cost or compromising. For example E-Tx was used to create the world’s first entirely fabric temperature sensor embedded within a composite, no additional components are necessary for temperature measurement, the embedded fabric is the sensor. Temperatures in the range of -50 to +250 °C can be measured with an accuracy of ± 0.5 °C, essential during launch testing of composite rockets. The E-Tx embedded sensors allow physical conditions in materials that could lead to failure of structures to be detected, etc.
Truely smart composites can be produced that incorporate a range of E-Tx embedded sensors and reactors. These reactive composites enable their properties to be tuned, as loads increase or temperature decreases the materials can heat up or cool down, expand or contract, flatten or twist, flex or stiffen, harden or soften, etc.
The areas of application for E-Tx and H-E-A-Tx technology in the composites industry falls into three sectors:
<!–[if !supportLists]–>1. <!–[endif]–>E-Tx Reactive Composites
<!–[if !supportLists]–>2. <!–[endif]–>E-Tx Sensory Composites.
<!–[if !supportLists]–>3. <!–[endif]–>E-Tx Moulds and Forms.
E-Tx reactive composites have been used for over three decades firstly in rocket casings and later in a wide range of applications including in pig stye floorings. Both examples show that E-Tx textiles in composites will survive for decades in the harshest conditions.
Moulds & Forms
1. As a replacement for conventional silicone encapsulated mat type wire heating elements.
2. As a captive heating element embedded within the composite structure to be used as a localised heat source for both pre-cure and post-cure operations.
3. Contained within the matting surfaces of mould tools to ensure even and uniform heat distribution throughout the entire tool effectively replacing conventional hot water / oil heating systems commonly used in moulding tools.
With conventional heat sources, such as silicone heater mats, the problem has always been that of poor conformity to shape and shortened life due to the metal element’s inability to flex for extended periods. When H-E-A-T textiles are employed as the heating element, the flexibility of a heater mat is increased immeasurably. Flex testing on H-E-A-T textiles has shown that they will operate without a drop in efficiency for hundreds of thousands of cycles.
The low voltage requirements of H-E-A-T make heating elements manufactured from the material an ideal portable heat source for in-field portable curing work stations for applications such as battle damage repair and stealth re-instatement.
In addition to the use of H-E-A-T as a stand alone heating element, the flexibility of the material makes it a first choice heat source for combining with sophisticated vacuum bagging systems. An ability to contour to complex 3-D shapes and compound profiles, coupled with the ability to be pierced, cut and lapped, gives H-E-A-T a unique edge over conventional heating media, thus allowing the manufacturer of composite parts to apply heat precisely and evenly with infinite control.
As a captive heating element in addition to triggering the curing process, H-E-A-T may be used as a heating element or conversely a temperature sensor during the working life of the composite structure containing it. For example, wing and rotor blade heating elements are an ideal illustration of this technology in use.
The ability to heat a moulding tool to a specific and controlled uniform temperature, is a distinct advantage in the manufacture of moulded product. Not only are the integrity and strength characteristics of the end product enhanced, but greater cost efficiency is achieved by decreased cycle times and faster arrival at mould operating temperature, thereby, achieving increased volume of product throughput.
In operations such as resin transfer moulding, mould temperature is a critical factor in achieving an end product with coherent strength characteristics. H-E-A-T offers the manufacturer the capability of uniform mould and lay-up temperature prior to resin infusion.