CN109592005B

CN109592005B - Design method of composite material stringer with notch

Info

Publication number: CN109592005B
Application number: CN201811318909.6A
Authority: CN
Inventors: 郑青泉; 何四海; 高伟
Original assignee: AVIC First Aircraft Institute
Current assignee: AVIC First Aircraft Institute
Priority date: 2018-11-07
Filing date: 2018-11-07
Publication date: 2021-10-15
Anticipated expiration: 2038-11-07
Also published as: CN109592005A

Abstract

The invention belongs to the field of airplane structure design, and particularly relates to a design method of a composite stringer with a notch. The method comprises the following steps: designing a non-gap composite material stringer, designing a chamfer angle at the gap of the stringer, designing a widened bottom edge near the gap of the stringer, designing a stringer end, and iteratively optimizing stringer parameters. The rib does not need to be notched, so that the strength of the rib is prevented from being weakened. Particularly for the wing surface structure with low wing profile height, the wing rib height is very low, and the condition of opening the notch requirement is difficult to even can not be met, so that the long purlin with the notch is very suitable for use. After the stringer web is ribbed and passes through the breach, widen the reinforcement through the bottom edge to and the beveling of web and bottom edge, realize the transition of load gradually, guarantee the smooth transmission of load along the stringer.

Description

Design method of composite material stringer with notch

Technical Field

The invention belongs to the field of airplane structure design, and particularly relates to a design method of a composite stringer with a notch.

Background

The design scheme has the advantages that the stringers are communicated along the span-wise direction, the continuity of stringer load transfer is ensured, and the stability of the wall plate is further ensured. The disadvantage is that the strength of the rib is correspondingly weakened after the rib is notched.

Particularly, for an airfoil structure with a low airfoil profile height, after the stringer of the wing rib passes through the notch, the residual effective cross-sectional area of the web plate is reduced in a large proportion, and even the bearing function of the rib cannot be met.

Disclosure of Invention

The task and purpose of the invention is to propose a composite stringer with a gap, which is particularly suitable for an airfoil structure with low airfoil height, and solves the problem that the rib height cannot meet the gap requirement of the stringer.

According to the invention, the rib passing notch is formed on the stringer web, the stringer bottom edge is reserved, the bottom edge is widened near the rib passing position, the rib is not notched, and the rib edge strip is attached to the stringer bottom edge after sinking at the stringer position, as shown in figure 2. The scheme avoids the wing rib in the low-wing airfoil structure from being excessively weakened by the stringer through the notch, and ensures the transfer of stringer load.

Technical scheme

The structural schematic diagram of the composite material stringer with the notch is shown in figure 3. On the basis of a common composite material T-shaped stringer, a notch is formed in a stringer web at the passing position of each rib through machining, and a skin, a stringer bottom edge and a rib edge strip are connected at the passing position of each rib through fasteners.

A design method of a composite stringer with a notch comprises the following steps:

1. and designing a composite stringer without gaps.

According to the bearing requirements of the stringers in the wallboard structure, the shape and the geometric dimension of the composite stringer and the composite material laying layer are designed according to the internal shape of the skin.

2. The stringer webs are ribbed through notches.

The stringer webs are notched according to the geometry of the ribs, leaving only the stringer bottom edges at the notches. Sufficient clearance must be left between the stringer gap and the rib to avoid the problem of the rib failing to assemble due to assembly errors.

3. Designing a chamfer angle at the notch of the stringer.

According to the load of the stringer, the web beveling angle at the notch is designed, so that the load on the stringer web smoothly transits to the bottom edge of the stringer. The web chamfer angles are rounded at both ends with R1 and R2 to avoid stress concentrations. The web radius R2 is spaced from the stringer root radius R5 by a distance K of at least 1 mm.

4. The widened bottom edge near the stringer gap is designed.

The stringer load carrying capacity is impaired due to the slitting of the stringer webs. According to the bearing requirements and the weakening degree of the bearing capacity, the bottom edge is widened, the widened part and the original structure bottom edge are transited through beveling, and the beveling starting point and the finishing point are rounded R3 and R4. The widening range is in the extending direction, and the distance D between the web plate beveling and narrowing starting point and the bottom edge beveling and narrowing starting point is not less than 10 mm. The widened trailing edge width B is determined by the intensity calculation.

5. Stringer end design.

The composite stringer and the skin are cured through secondary bonding, and the stringer and the skin are connected through a plurality of fasteners at the ends of the stringer, so that the stringer is prevented from being stripped. Thus, the stringer end bottom edges should be designed according to the peel resistant fastener margin requirements. The web at the stringer end should be chamfered or filleted.

6. And (4) iteratively optimizing stringer parameters.

And performing intensity calculation and optimization iteration on the basis of the design, and finally designing a group of parameters meeting the intensity requirement. And in the step 2, the gap between the stringer notch and the rib is 2 mm.

And the recommended value of the chamfer angle in the step 3 is 20-30 degrees.

The recommended value of the chamfer angle of the bottom edge in the step 4 is 30 degrees.

The R1 to R5 are different corner marks and do not represent the corner size.

Technical effects

The composite material stringer with the notch has the advantages that notches are not required to be formed in wing ribs, and therefore the strength of the ribs is prevented from being weakened. Particularly for the wing surface structure with low wing profile height, the wing rib height is very low, and the condition of opening the notch requirement is difficult to even can not be met, so that the long purlin with the notch is very suitable for use. After the stringer web is ribbed and passes through the breach, widen the reinforcement through the bottom edge to and the beveling of web and bottom edge, realize the transition of load gradually, guarantee the smooth transmission of load along the stringer.

Drawings

FIG. 1 is a view of a rib stringer passing through a gap

FIG. 2 is a view of a stringer with a cut-out through the rib

FIG. 3 is a view of a composite stringer with a gap

FIG. 4 is a typical notch of a stringer and its auxiliary view (front view)

FIG. 5 is a typical gap of a stringer and its auxiliary view (top view)

FIG. 6 is a typical notch of a stringer and its auxiliary view (cross-section)

FIG. 7 is a flow chart of a design method of the present invention

Detailed Description

Designing a composite material T-shaped stringer laying layer according to the stringer load; designing the size of the stringer slit according to the position and size of the rib; designing the parameters of the bottom edge widening beam, the web plate, the bottom edge chamfer angle and the like which meet the strength requirement and are shown in figure 4; the two ends of the stringer are provided with a bottom edge widening beam, a web plate, a bottom edge chamfer angle and a fillet according to the requirements of the number, the edge distance and the end distance of the stripping fasteners. The manufacturing is carried out according to the design drawing.

A composite stringer with a notch is characterized in that on the basis of a common T-shaped composite stringer, a rib is machined on a stringer web plate to pass through the notch, and the bottom edge of the stringer at the notch is widened. To ensure smooth transfer of stringer loads, the following parameters in FIG. 4 must be validated by strength calculations:

1 stringer height H.

2 stringer bottom edge thickness δ.

3 web chamfer angle beta.

4 bottom edge chamfer angle alpha.

5 round corner transitions to avoid stress concentration, R1, R2, R3, R4, R5.

6 the width of the bottom edge is increased from A to B, and the widening amount is determined according to the intensity calculation.

7 the distance D between the starting point of the web plate beveling and narrowing and the starting point of the bottom edge beveling and narrowing.

8 rounded corner R2 is spaced from rounded corner R5 by a minimum distance K.

9 the bottom edges of the stringer ends are suitably widened to ensure sufficient space for the peel fasteners. The web and the bottom edge have appropriate chamfer angles and round corners.

Claims

1. A design method of a composite stringer with a notch is characterized by comprising the following steps:

1) designing a composite material stringer without gaps:

designing the shape and the geometric dimension of the composite material stringer and the composite material laying layer according to the bearing requirements of the stringer in the wallboard structure and the internal shape of the skin;

2) the stringer web is ribbed and notched:

according to the geometrical shape of the rib, a notch is formed in the stringer web, and only the stringer bottom edge is reserved at the notch; enough clearance must be left between the stringer gap and the rib to avoid the problem that the rib cannot be assembled due to assembly error;

3) designing a chamfer angle at the notch of the stringer:

according to the load of the stringer, designing a web plate beveling angle at the notch to enable the load on the stringer web plate to be smoothly transferred to the stringer bottom edge; the two ends of the chamfer angle of the web are rounded R1 and R2 to avoid stress concentration; the web radius R2 is at least 1mm from the stringer root radius R5 by K;

4) design of widened bottom edge near stringer gap:

the bearing capacity of the stringer is weakened due to the notch of the stringer web; according to the bearing requirements and the degree of bearing capacity weakening, widening the bottom edge, enabling the widened part to be in transition with the bottom edge of the original structure through beveling, and rounding R3 and R4 at the starting point and the ending point of the beveling; the widening range is in the extending direction, and the distance D between the web plate beveling narrowing starting point and the bottom edge beveling narrowing starting point is not less than 10 mm; the width B of the widened bottom edge is determined by intensity calculation;

5) designing a stringer end:

the composite material stringer and the skin are cured through secondary cementing, and the stringer and the skin are connected by using a plurality of fasteners at the end of the stringer, so that the stringer is prevented from being stripped; therefore, the bottom edge of the stringer end is designed according to the edge distance requirement of the anti-stripping fastener; the web plate at the end of the stringer is designed with beveling and rounding;

6) and (3) iterative optimization of stringer parameters:

and performing intensity calculation and optimization iteration on the basis of the design, and finally designing a group of parameters meeting the intensity requirement.

2. The method of claim 1, wherein the stringer slit-rib spacing in step 2) is 2 mm.

3. The method of claim 1, wherein the chamfer angle in step 3) is 20 ° to 30 °.

4. The method of claim 1, wherein the chamfer angle of the bottom edge in step 4) is 30 °.