GB/T 39491-2020 English PDF (GBT39491-2020)

Delivery: 3 seconds. Download true-PDF + Invoice.
Get QUOTATION in 1-minute: Click GB/T 39491-2020
Historical versions: GB/T 39491-2020
Preview True-PDF (Reload/Scroll if blank)

GB/T 39491-2020: General technical requirements of carbon fiber composites covering parts for automobiles
GB/T 39491-2020
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 83.120
Q 23
General Technical Requirements of Carbon Fiber
Composites Covering Parts for Automobiles
ISSUED ON: NOVEMBER 19, 2020
IMPLEMENTED ON: OCTOBER 1, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative References ... 4 
3 Terms and Definitions ... 5 
4 Materials ... 6 
5 Processes ... 7 
6 Requirements ... 8 
7 Test Methods ... 10 
8 Inspection Rules ... 11 
9 Marking, Packaging, Transportation and Storage ... 12 
Appendix A (normative) Appearance Determination of Parts ... 14 
Appendix B (normative) Test Method for Gravel Impact Resistance ... 16 
General Technical Requirements of Carbon Fiber
Composites Covering Parts for Automobiles
1 Scope
This Standard specifies the materials, process, requirements, test methods, inspection rules,
marking, packaging, transportation and storage of carbon fiber composites covering parts for
automobiles.
This Standard is applicable to carbon fiber composites covering parts for automobiles that are
molded through prepreg compression molding, wet compression molding and carbon fiber
sheet molding compound compression molding (hereinafter referred to as parts). The covering
parts molded through other processes may take this as a reference.
2 Normative References
The following documents are indispensable to the application of this document. In terms of
references with a specified date, only versions with a specified date are applicable to this
document. In terms of references without a specified date, the latest version (including all the
modifications) is applicable to this document.
GB/T 1184 Geometrical Tolerancing - Geometrical Tolerance for Features without Individual
Tolerance Indications
GB/T 1447 Fiber-reinforced Plastics Composites - Determination of Tensile Properties
GB/T 3365 Carbon Fiber Reinforced Plastics - Determination of Void Content and Fiber
Volume Content
GB/T 3961 Terms for Fiber Reinforced Plastics
GB/T 4780 Terms for Motor Vehicle Body
GB/T 5258 Fiber-reinforced Plastic Composites - Determination of Compressive Properties in
the in-plane Direction
GB/T 10125 Corrosion Tests in Artificial Atmospheres - Salt Spray Tests
GB 11566 External Projections for Passenger Car
GB/T 13657 Bisphenol-A Epoxy Resin
GB/T 19466.2 Plastics - Differential Scanning Calorimetry (DSC) - Part 2: Determination of
Glass Transition Temperature
GB/T 26752 PAN-based Carbon Fiber
GB/T 28461 Carbon Fiber Prepreg
GB/T 28889 Test Method for In-plane Shear Properties of Composite Materials
GB/T 30021 Warp Knitting Carbon Fiber Reinforcements
GB/T 30512 Requirements for Prohibited Substances on Automobiles
QC/T 15 General Test Methods for Automotive Plastic Products
QC/T 17 General Rules for Weather Resistance Test of Automotive Parts
QC/T 966 Coating Technical Conditions for Automotive Plastic Parts
3 Terms and Definitions
What is defined in GB/T 3961 and GB/T 4780, and the following terms and definitions are
applicable to this document.
3.1 Covering Parts
Covering parts refer to panels covering the surface of the body frame.
NOTE: in accordance with functions and positions, covering parts can be divided into three
categories: external covering parts, internal covering parts and skeleton covering parts.
3.2 Prepreg Compression Molding
Prepreg compression molding refers to a preparation technology of placing prepreg in a metal
mold, and at a certain temperature, pressurizing and curing it into composite products.
3.3 Wet Compression Molding
Wet compression molding refers to a rapid preparation technology of laying the properly cut
carbon fiber cloth on the surface of the mold and spraying it with resin, so that resin can infiltrate
fibers, then, solidifying it into composite products after clamping, pressurizing and heating.
3.4 Carbon Fiber Sheet Molding Compound
Carbon fiber sheet molding compound refers to a type of molding compound made of resin
paste impregnated with carbon fiber or chopped carbon fiber felt, and covered with
polyethylene film on both sides.
5 Processes
5.1 Prepreg Compression Molding
The prepreg compression molding process shall comply with the following requirements:
a) In accordance with the design documents, lay up; the layups shall be symmetrical and
balanced;
b) The starting point for laying fibers shall be reasonably selected;
c) When adopting the pre-forming process, the mold surface shall be reasonably selected
in accordance with the appearance requirements;
d) When the thickness of the structure changes, the thickness transition area shall be
reasonably designed; the layups shall be alternatively removed / added between
successive layups; the external layups shall continuously cover the entire surface;
e) The deviation of the layup angle from the laying outline dimension line and the layup
angle marking line shall not exceed  7;
f) When carbon fiber parts are in direct contact with metal parts, in order to avoid
electrochemical corrosion, an insulating layer can be set up on the surface, and its
thickness shall be determined in accordance with the actual design requirements of
the parts;
g) For parts that have rigorous requirements towards tolerances, and whose dimensional
tolerances cannot be directly obtained through molding, allowances for machining
shall be reserved.
5.2 Wet Compression Molding
The wet compression molding process shall comply with the following requirements:
a) In accordance with the design documents, lay up; the layups shall be symmetrical and
balanced;
b) The layup angle and the number of layups shall satisfy the design requirements.
During the fabric laying process, wrinkling of the fabrics shall be avoided;
c) When the thickness of the structure changes, the layups shall be alternatively removed
/ added between successive layups; the external layups shall continuously cover the
entire surface;
d) For splicing parallel to the fiber direction, butt joint shall be adopted; for splicing
perpendicular to the fiber direction, lap joint shall be adopted; the fabrics shall not be
butted;
e) The minimum fillet radius R generally depends on the laminate thickness t and the
mold. It is recommended to use R  Max (t/2, 3 mm);
f) The spraying, flowing and impregnating process of the resin shall be controlled in
accordance with the pre-determined path, so as to ensure that the resin completely
impregnates the fiber under pressure, and that no defects like lacking resin or excess
resin appear. The resin shall be rapidly cured at a pre-determined temperature, and
simultaneously, the phenomenon of implosion shall be avoided;
g) During the curing process, it shall be ensured that each area of the parts is uniformly
heated with a temperature difference of not greater than 5 C.
5.3 Carbon Fiber Sheet Molding Compound Compression Molding
The carbon fiber sheet molding compound compression molding process shall comply with the
following requirements:
a) In accordance with the structure and shape of the parts, and the flowing properties of
the materials, determine the cutting requirements. The materials are mostly cut into
rectangles or circles. When multiple layers of materials are superimposed, they shall
be stacked in the shape of a pagoda;
b) The material...