article jec magazine 80 hexcel

7/28/2019 Article Jec Magazine 80 Hexcel

1/3

reinforcement

36 jec composites magazine / No80 April - May 2013

Succeeding wood, aluminiummetal was for a long time theonly material capable of provi-

ding the desired material performancein relation to its weight. Step by step,

composites have replaced aluminiumin aircraft structures, gradually rea-ching the current levels of over 50%of the structural weight of an aircraft.The latest generation aircraft have a

very high level of carbon f ibre compo-sites in their structure, proving againthat the main driver i n aerospace is

weight saving.

Starting with military and industrialapplications and evolving into com-mercial aircraft structures, prepreg

technology has adapted to the marketneeds. Major developments camefrom material characteristics provi-ding on-demand performance, inclu-ding fast cure cycles for industrialapplications, high servi ce temperatureperformance for engines, and impacttolerance for primary structures.Prepreg is a baseline technology inthis industry because of its bettercost-performance ratio compared to

competing materials and its materialand technology reliability.

In addition to the constant deve-lopment of new high-performancecomposite materials, the market alsorequired more robust manufacturingprocesses primarily to ensure higher

quality standards, especially for largecomposite structures. Automatedfibre placement (AFP) and automatedtape laying (ATL) were developed andimplemented to provide OEMs thetools for producing these high-qualityparts.

The right material andtechnology at the right placeDespite the maturity of prepregtechnology, OEMs are continuouslylooking for alternatives for the future.

Is prepreg technology the only answerfor all the primary structures of next-generation aircraft?

Although, up to now, the cost-per-formance ratio achieved with pre-preg technology has allowed theapplications for high-performancecomposites to increase, this will notnecessarily be the case for all next-

An innovative composite solution for

cost-effective primary aircraft structures

Flying a structure with a mass heavier than air necessitates the

use of the lightest possible materials with the highest possible

performance-to-mass ratio. Since the early years of aviation, air-

craft builders have worked to reduce the weight of their planes.

HiTape, the Hexcel innovative Unidirectional Dry reinforcement is

used to build aircraft structures.

generation aircraft primary structures.While weig ht was the main driver forcomposite applications in the past, anew weight-cost trade-off will drivethe material and technology choicefor next-generation aircraft. This newsituation opens the door to othermaterials and technologies, including

a return to metal with new-generationalloys.

The challenge facing aircraft designersis to find, to develop and to certify theright materials and technology on apart-by-part basis, to balance overalloptimum performance and final partcosts with a minimum industrial riskand with a mature supply chain.

Alternativecomposite technologies

From the early days of compositematerials, alternative f ibre-reinforce-ment matrix technologies to prepreghave existed. When looking at newcost-performance trade-offs, onecategory stands out above all others:liquid composite moulding (LCM:RTM and infusion) materials.

LCM materials have been studied andused in aircraft secondary structures

ByHenri Girardy, Business Development

Manager new Processes

Jean-Marc Beraud,

Reinforcements R&T Manager

Hexcel Corporation


2/3

hygrothermal ageing.

HiTape Combining currenttechnology advantages with

increased cost effectivenessHexcels innovative proposal is tocombine the benefits of automationand the cost effectiveness of infusion/injection technologies with the highperformance of latest-generation pre-preg materials.

The new proposal is the missing linkbetween interest ing but incompletecurrent LCM materials and latest-ge-neration prepregs in term of perfor-mance-cost ratios.

Performance in composites comesfrom straight, perfectly aligned fibres;HiTape is therefore a unidirectionaltape. Made from Hexcels HexTowcarbon fibre and combined with Hex-Flow infusion resin, HiTape matchesthe performance of the latest-genera-tion UD prepregs.

Wh ile offering the same overall in-plane mechanical performance levelas state-of-the-art prepreg materials

thanks to the equivalent 60% fi brevolume content achieved by vacuuminfusion, another major innovation ofHiTape is to improve the toughnessof current composites made by LCMtechnologies.

for many years, and some are evenused now for primary aircraft struc-tures on a small scale. Hexcel has beena leader in the development of thistechnology through a large num-

ber of qualif icat ions for HexForcereinforcements and HexFlow RTM6resin. Woven fabrics and non-crimpfabrics (NCF), when combined withthe appropriate resin infusion andinjection process, can provide a posi-

tive performance/cost balance. Costsavings have been demonstrated inpart design, function integration, lessassembly time, and potentially fewerfinishing operations.

However, these materials do not fully

meet the mechanical performance re-quirements or the quality standards ofprimary structures due to the manuallay-up process of the dry preform. Theemerging automated pick and placeof woven or NCF materials can only

be seen as a step toward the ultimateautomated solution, combining ascrap-free process with optimumdesign possibilities.

Despite the interest in higher deposi-tion rates, major drawbacks of currentNCF materials include a lack of designfreedom, ply stop minimum thic-kness, high scrap levels, inadequatemechanical performance (in particulartoughness) and microcracking after

No80 April - May 2013 /jec composites magazine 3

Fig. 1: HiTape : Innovative composite route for cost-effective primary aircraft structures

Fig. 2: HiTape : Similar performance to latest generation prepreg Fig. 3: HiTape : breakthrough in CAI


3/3

prietary fuzz- and splice-free techno-logy, greatly facilitates the preformmanufacturing process, inducingfewer stoppages due to f ibre breakage

or equipment cleaning during lay-up.

Moreover, the material does not useany carrier film, so the machines aresimpler, not dependent upon roomtemperature or humidity for tackcontrol, and therefore more efficient.In consequence, outputs of 50kg/hare anticipated depending on partdesign. In addition, the material doesnot require any refrigerated storage.Hexcel is working closely with severalmajor OEMs to demonstrate the

benefits of thi s material throughvarious developments and demonstra-tor programmes.

HiTape is a Hexcel registered trade-mark and the product is patented. n

More information:

www.hexcel.com

With standard dry unidirectional tape,through-the-thickness resin permea-

bil ity is a clear limitat ion for thickparts. Thanks to proprietary techno-

logy, HiTape is available in di fferentvers ions enabli ng vacuum infusion ofparts up to 30mm thick with a 58 to60% fibre volume content.

To make high-quality parts, a f ully-controlled automated process is nee-ded. Hexcel has worked closely withautomated machine manufacturersto bring HiTape to the market withthe maturity required using currentconventional automated placement

AFP or ATL machines .

The tight wi dth tolerance achievedwith HiTape, assoc iated with a pro-

reinforcement

38 jec composites magazine / No80 April - May 2013

Fig. 4: Hitape : 30mm thick panel IMA 12K/RTM6 Vacuum infusion 58%FVC

Fig. 5: HiTape: ATL and AFP reinforcements

HiTape combines the benefts o automation o dry preorm manuacturing and cost-eec-

tiveness o inusion/injection technologies with the high perormance o latest-generation

prepreg materials. This new unidirectional tape is available in dierent versions enabling

vacuum inusion o parts up to 30mm thick with a 58 to 60% fbre volume content. This dry

reinorcement is expected to allow outputs o 50kg/h depending on part design.

More informationMore information

article jec magazine 80 hexcel

Documents