Description:Complete Specification of
Hybrid light weight door handles for aircrafts and manufacturing method thereof


1 Title of the Invention
Hybrid light weight door handles for aircrafts and manufacturing method thereof
2 Field of the Invention
The invention relates to the field of advanced fiber epoxy composite parts manufacturing, more significantly on the method of fabrication of a hybrid light weight composite door handles for advanced light Helicopters.
3 Background of the Invention
Weight of an aircraft is a prime concern and a challenge for aircraft designers; efforts have been put to minimize the basic weight of the structural parts by introducing high strength to low weight materials and innovative ways to fabricate the parts.
The present innovation describes a sandwich structure door handle having excellent characteristics of light weight, thin section (good grip), and rigidity; more specifically, the invention relates to the method of integrating a specific low density core material, chopped strands mixed with resin and a fiber-reinforced material for a skin to fabricate hybrid sandwich door handles with special characteristics.
More than 40 % is covered with fibers of discontinuous reinforcing glass fibers crossing each other through the thermosetresin. The challenging feature in the invention is to fabricate a composite sandwich component to have both rigidity and light weight, and to produce a thin-walled shaped body having complex shape with good mass distribution.
3.1 Prior Art and drawbacks with the present invention
Prior arts related to the invention or the existing process in the field of the composite parts and its fabrication is mentioned in the embodiments CN103979099B, ES2719499T3, JP6752860B2, EP2759470B1, EP3095 590 B1.

Prior Art Claims of the Prior Art Drawbacks / Comparison with the present invention

CN103979099B
The claims of the invention relate to a method of making composite structures having gap fillers with a chopped fiber material. It describes a method of applying chopped fiber material in varying thicknesses onto a first ply surface to form a layered composite charge. The method further includes the step of folding the layered composite charge and assembling a second composite charge and the folded layered composite charge to form a composite structure. The chopped fiber material forms gap filler in the composite structure. The gap filler conforms to a shape of the composite structure surrounding the gap filler. The present invention claims a method of making a hybrid sandwich light weight door handles that comprises of chopped fiber glass mixed with epoxy resin and integrated with the low density foam, whereas the earlier invention claims for chopped fibers as the gap fillers to conform the shape of the composite structure, the object of the present invention is to provide an integrated molded body that is lightweight and excellent in rigidity by integrating such a sandwich structure with other members. another object of the present invention is to provide a method for manufacturing a core structure or an integrated molded product. Hence the claims of the earlier art have no relevance with the present invention.

ES2719499T3
The claims of the invention describe a molded product of surface layer and a protruding core, the surface layer being a reinforced fiber and a matrix resin, also part of the reinforcing fiber threads extending penetratingly between the surface layer part and the core part, the part of the reinforcing fiber threads extending penetratingly at a rate of 400 threads / mm2 or more.

The present invention claims a method of making a hybrid sandwich light weight structural with prepreg layers as the skin layers instead of fiber threads and foam in the middle integrated on both sides with the chopped fiber epoxy member, the present invention describes a method to integrate the skin layers, foam and the chopped fiber member Hence the claims of the earlier art doesn’t have any relevance with the present invention.
JP6752860B2 The claims of the embodiment describes a composite skin containing multiple reinforcing fibers embedded in a polymer matrix of polymer resin, A second composite skin containing a plurality of reinforcing fibers embedded in the polymer matrix of the polymer resin , and between the first composite skin and the second composite skin and bonded to them. A polymer core containing a plurality of cells defined by corresponding cell walls, which is substantially perpendicular to the first composite skin. A foam that binds the polymer core to the first composite skin.
The object of the present invention is to describe a method of manufacturing aintegrated molded product formed by joining a first member composed of a molded discontinuous fiber epoxy member and machined low density foam. Whereas the earlier invention claims the foam embedded with multiple skin layers, however the earlier claims have no relevance to the present invention.
EP2759470B1 The claims of the invention as per the embodiment the method of manufacturing an aircraft box structure for carrying load that comprises
upper and lower composite integrated sandwich panels. these integrated sandwich panels having face sheets, one or more core portions and spars with each spar comprising web and its attachments. The present invention claims for the method of manufacturing hybrid sandwich door handle which doesn’t comprise the core, spars and the face sheets as it is described in the earlier art, hence the present claims are not related to the claims of the invention.
EP3095 590 B1.
The invention claims for a carbon fiber reinforced polymer panel arrangement comprising at least one carbon fiber reinforced polymer panel that is provided with interlocking elements associated with a zip fastener said interlocking elements being rigidly attached to an associated interlocking element tape, the associated interlocking element tape is sewed to at least one carbon fiber reinforced polymer panel comprises a carbon fiber reinforced polymer fabric that is infused with epoxy resin. The present invention is related to a sandwich structure comprising a pre-cured chopped glass fiber member integrated with the foam without any interlocking elements nor the polymer fabric infused with the epoxy resin as claimed in the claims of the prior art, Hence the claims of the previous art have no relevance to the present claims.

4 Brief Summary of the Invention

An object of the present invention is to manufacture hybrid sandwich door handle assembly having excellent lightweight and rigidity by integrating a sandwich structure with pre-cured member (2) and machined foam (1). Another object of the present invention is to provide a method for manufacturing integrated molded sandwich product with good mass distribution (20). Good mass distribution ensures adequate strength at the assembly area, relatively thin section and good hold at gripping area.
A sandwich door handle assembly comprising discontinuous reinforcing glass chopped strands that are made by bundling thousands of E-glass fiber together and chopping them into specified length. Chopped Strands are used in combination with high-performance epoxy resin and pre-cured at room temperatures before it (2) is integrated with low density foam (1) and the skin material (5) (6). More than 40% of the handle assembly comprises of chopped fibers mixed with epoxy resin. The Chopped glass procured member (2) is not just used as a filler material, but it is a structural load bearing constituent of the handle assembly unlike in the prior art. It is challenging to integrate the pre-cured member (2) with foam (1) and prepreg skin layers (5) (6) to obtain high strength, light weight sandwich integrated molded product.
In the present invention, Embodiments described herein relate to composite structures or sandwiches that have relatively high bending stiffness and relatively light weight, it also includes a method of assembling a pre-cured stack (2) embedded within the prepreg layers (5) (6) and applying temperature (18) & pressure (19) to achieve void free bonding between the skin layers (5) (6), foam (1) and the pre-cured discontinuous fiber epoxy stack (2).
Features from any of the disclosed embodiments may be used in combination with one another, without limitation. In addition, other features and advantages of the present disclosure will become apparent to those of ordinary skill in the art through consideration of the following detailed description and the accompanying drawings.
5 Detail Description of the Drawings
The invention can be better understood by reading the detail description of the disclosed embodiment followed by the accompanied drawings.
Figure 1: shows the cross sectional view of the sandwich hybrid door handle that shows the pre-cured chopped glass fiber epoxy member (2) machined low density 51WF foam (1) that are embedded with the multiple skin layers (5) & (6)
Figure 2: shows the the door handle depicting how foam (1) is assembled physically to its ends with chopped glass fiber stack (2) with the use of Foaming adhesive (3) resulting in required mass distribution (20).
Figure 3: Error! Reference source not found.shows the door handle with drilled holes diameter 5 mm (7) and spot face of diameter 14 mm (8).
Figure 4: shows the Top, Front and side view of the sandwich door handle with drilled holes (7) & spot faced (8) at hole location to facilitate seating of fasteners.
Figure 5: shows the Closed mould with top (12) and bottom (13) moulds along with the positioning arrangement (9) (10) & locating pins (14) (15)
Figure 6: shows the bottom mould (13) of the tool with the handle positioning cavity (11).
Figure 7: shows the top mould (12) of the tool with the handle positioning cavity (11).
Figure 8: shows the mould (16) for casting the chopped glass fiber epoxy stack/member (2).
Figure 9: shows the cavity (17) of the mould (16), that is used for casting the chopped glass fiber epoxy stack/member (2).
Figure 10: shows the two step (double dwell) cure cycle comprising the temperature profile (18) and pressure profile (19).
6 Detail Description of the Invention
The present invention describes method of fabrication of hybrid sandwich door handle assembly having light weight and rigidity, which comprises of integrating pre-cured chopped glass fiber member (2) and machined foam (1) with prepreg skin layers (5) (6) to obtain a sandwich product with good mass distribution (20).
The pre-cured member (2) comprises of chopped E- glass fibers mixed with epoxy resin and casted using a closed mould tool (16). Chopped E- glass fibers and resin are mixed in a definite proportion of 50:50 gms parts by weight (pbw). The epoxy resin that is mixed with E-glass fibers has two parts - resin (part A) and hardener (part B) mixed in a ratio of 100:25 pbw. The mixed heterogeneous mixture of E-glass fibers and resin is poured in to the cavity (17) of the casting tool (16) and allowed to cure under room temperature for 24 hours.
The low density polymeric structural foam is used for lightweight sandwich component designs that require high shear and pressure resistance, even at elevated temperatures. The foam stock is cut to the required size 20MM X 9MM X 89 MM as per the drawing and the contour is machined and ensured using contour check templates. The said machined foam (1) is sandwiched between skin layers (5) (6). The machined foam (1) lends the skins (5) (6) support to form the shape, and significantly increases the rigidity of the composite structure.
The weight of the core/foam (1) material is significantly lower than that of equivalent skins that would have been necessary to achieve comparable rigidity and ability to withstand high stresses. The ends of the machined foam (1) are bonded with pre-cured E-glass epoxy members (2) using foaming adhesive (3) that is typically used for bonding of inserts or edge members to core/foam and localized reinforcement of honeycomb cores where increased shear strength is required.
A toughened, general purpose aerospace epoxy film adhesive (4) is used over the surface of the bonded member that has the foam (1) and the pre-cured glass member (2) to provide excellent structural performance and to provide outstanding durability in bonding with skin layers (5) & (6).
The skin layers (5) & (6) are the prepreg layers of Kevlar fabric with 54% of epoxy resin that has excellent chemical stability at high temperature and resistance to wear, combined with glass fabric with 37% of epoxy resin. Kevlar provides better flexural and tensile strength when combined with the glass fabric. Also the glass fabric that is placed over the Kevlar fabric, provides better tensile strength and avoids fiber pullout and local delaminations during drilling.
Referring to Figure 1 one layer of resin film (4) is laid over the bonded member of procured E-glass epoxy (2) and polymeric foam (1), subsequently two layers of kevlar (5) prepreg is laid over the resin film (4) and a glass layer (6) is laid over the kevlar layers, finally one layer of peel ply is laid over the glass layer to achieve the consistent surface for secondary bonding or painting.
The tool comprising top (12) and bottom (13) moulds along with the positioning arrangement (9) (10) & locating or guiding pins (14) & (15) is designed to cure the sandwich door handles in autoclaves or using hot platen press. The component is placed in the cavity (11) of the bottom mould (13) after final layup of skin layers (5) (6) and the top mould (12) is placed exactly over the bottom mould (13) with the help of positioning arrangement (9) (10), guiding pins (14) & (15). Later the vacuum bagging (21) is carried out and cured in autoclave as per the cure cycle (Fig. 10) where the temperature profile (18) and the pressure profile (19) is monitored continuously during curing. The temperature profile (18) comprises of two ramps with a controlled heat up rate less than 2deg.C/min and two holds with 45 min at 80 deg.C and 60 min at 135 deg.C. The pressure profile (19) comprises of two steps with low pressure applied initially at a controlled pressurisation rate to avoid the foam crush and warpages in skin layers. As the temperature reaches to the resin liquid / gel condition, final cure pressure is applied for better consolidation of layers.
After curing the top mould (12) is detached from the bottom mould (13) and the cured door handle assembly is demoulded / separated from the bottom mould (13). Later the component is trimmed to remove the resin flashes and the edges are sealed by resin touch up. The holes of diameter 5mm (7) are drilled on either side of the handle. The spot facing of diameter 14 mm (8) is carried as shown in the fig.3. The peel ply layer is then removed for surface preparation and the handle is painted.
, C , C , Claims:Title: Hybrid light weight door handles for aircrafts and manufacturing method thereof

We Claim,
1. A method for fabrication of hybrid light weight sandwich door handle assembly with good mass distribution (20), comprising
- Two pre-cured members (2) of chopped E- glass fibers mixed with high performance epoxy resin utilizing curing mould (16) and comprising more than 40% by weight;
- Machined polymeric low density foam (1);
- A foaming adhesive (3) to bond the pre-cured stack (2) with the foam (1);
- A film adhesive (4) to create a bonding surface between the skin layers (5) (6), and the integrated assembly of foam (1) and pre-cured stack (2);
- Wrapping of Skin layers of Kevlar and glass prepreg (5) & (6) over the bonded assembly of foam (1) and pre-cured members (2);
- Laying up Peel ply layer over the skin layers (5) (6) to create secondary bonding surface;
- Positioning the laid up stack into the cavity (11) of the bottom & top moulds (12) (13);
- Curing the vacuum bagged Closed mould (12) (13), also comprising the laid up up stack, under controlled cure parameters of
o temperature (18) further comprising of two ramps with a controlled heat up rate less than 2deg.C/min and two holds with 45 min at 80 deg.C and 60 min at 135 deg.C;
o & pressure (19), further comprising of two steps, with low pressure 100 KPa applied initially at a controlled pressurisation rate to avoid the foam crush and warpage in skin layers, and high cure presseure 200 KPa applied for better consolidation of layers as the temperature reaches to the resin liquid / gel condition;
2. As per Claim 1, the said pre-cured members (2) further comprising of chopped E-glass fibers and epoxy resin; where chopped E- glass fibers and resin is mixed in a definite proportion of 50:50 gms, and the epoxy resin that is mixed with E-glass fibers has two parts - resin (part A) and hardener (part B) mixed in a ratio of 100:25 pbw (parts by weight); the mixed heterogeneous mixture of E-glass fiber and resin is poured in to the cavity of the casting mould (16) and allowed to cure under room temperature for 24 hours;
3. As per Claim 1, the said machined foam (1) is bonded with pre-cured E-glass epoxy members (2) using foaming adhesive (3);
4. As per Claim 1, the said Closed mould comprising Top mould (12) & Bottom mould (13) further comprising the positioning arrangement (9) (10) & locating pins (14) (15).