Thermoplastic-Surface Prepreg for Complex Mold Conformability
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Solution Overview
Problem
Existing fiber-reinforced composite materials face challenges in producing complicatedly shaped parts due to rigidity and poor adhesion to molds, leading to prolonged production times and reduced material strength, especially when using thermosetting resins and mechanical or adhesive joining methods.
Innovation Solution
A prepreg comprising reinforcing fibers impregnated with a thermosetting resin, with a thermoplastic resin on at least one face, exhibiting specific loss tangent and loss angle characteristics, allowing for flexible adhesion and moldability on complex shapes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thermosetting resin is used as a matrix in fiber-reinforced composite materials, then mechanical properties such as strength, stiffness, and heat resistance are improved, but the material becomes rigid and difficult to form on complicated mold shapes
Solution Approach 1:
The patent applies parameter changes by controlling the gel fraction of the thermosetting resin within a specific range (20-80%) to achieve an optimal balance between mechanical strength and flexibility. This parameter control allows the material to maintain strength while gaining enough flexibility to conform to complicated mold shapes during the molding process
Solution Approach 2:
The patent creates a composite material system combining thermosetting resin (for strength) with specific gel fraction characteristics (for flexibility). This composite approach allows the material to exhibit both high mechanical strength and adequate formability, resolving the contradiction between these two properties
2Stability of the object's composition
If a cured thermosetting resin is used on the surface of the composite material, then structural integrity is improved, but the surface loses tackiness and cannot be accurately fixed at desired positions in a mold
Solution Approach 1:
The patent controls the gel fraction parameter of the thermosetting resin to maintain structural integrity while preserving surface tackiness. By keeping the gel fraction within 20-80%, the cured resin maintains its structural properties while retaining enough surface adhesion to be accurately positioned in the mold
Solution Approach 2:
The patent applies local quality by ensuring the thermosetting resin has appropriate gel fraction characteristics throughout the material structure, allowing different regions to exhibit both structural integrity and surface tackiness as needed for molding and positioning
3Strength
If mechanical joining methods using bolts or rivets are used to integrate composite material members, then connection strength is achieved, but production time increases and material strength decreases due to drilling
Solution Approach 1:
The patent merges the composite material members into a single integrally molded article through direct molding, eliminating the need for separate mechanical joining operations. This combining approach maintains connection strength while significantly reducing production time by removing drilling, assembly, and fastening steps
4Strength
If adhesive joining methods are used to integrate composite material members, then connection is achieved, but production time increases due to adhesive preparation, application, and curing steps
Solution Approach 1:
The patent merges multiple members into a single integrally molded article, eliminating the need for separate adhesive joining operations. This approach maintains adequate connection strength while dramatically reducing production time by removing adhesive preparation, application, and extended curing steps
Solution Approach 2:
The patent extracts the adhesive joining process entirely from the manufacturing sequence by achieving direct integral molding. This extraction eliminates the time-consuming adhesive steps while maintaining structural integrity through the molded integration
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The prepreg provides suitable flexibility and tackiness, enabling efficient formation of high-quality, complex-shaped fiber-reinforced composite materials without positional shifts, with enhanced adhesion and integration strength.
Implementation Method 1
a gel fraction of the thermosetting resin in the prepreg is 20% or more and 80% or less
Implementation Method 2
the prepreg is allowed to stand for a predetermined time or less in a state where the face containing the thermoplastic resin is in contact with a mold for injection molding or a mold for compression molding, and then, heating and pressing are performed to cure the thermosetting resin
Data Source
Figure 1~2(c)
Figure 3~4
Figure 5(a)~5(d)
AI summary
A problem to be solved by the present invention is to provide a prepreg and an integrally molded article, wherein the prepreg exhibits suitable flexibility and adhesiveness, excels in formability on a complicated mold face and adhesion to a mold face, causes no positional shift, and can be efficiently reinforced and stiffened at an intended position. A main object of the present invention is to provide a prepreg including (A) reinforcing fibers, (B) a thermosetting resin, and (C) a thermoplastic resin, wherein the (C) thermoplastic resin exists in at least a part of a face of the prepreg, and wherein the prepreg satisfies the condition [I], and satisfies the condition [II] or the condition [III]: [I]: the (B) thermosetting resin has a peak in the temperature range of more than 100°C and 180°C or less on a loss tangent (tan δ) curve measured under isokinetic heating by dynamic mechanical analysis (DMA); [II]: on a loss angle δ curve obtained by measuring the prepreg isothermally by dynamic mechanical analysis (DMA), the loss angle δ curve has a point representing the maximum value, and has a point which represents a loss angle δ value 5° or more smaller than the maximum value, and which is on the earlier time side of the point representing the maximum value; and [III]: even if, on the loss angle δ curve obtained by measuring the prepreg isothermally by dynamic mechanical analysis (DMA), the loss angle δ curve has a point representing the maximum value, the loss angle δ curve does not have a point which represents a loss angle δ value 5° or more smaller than the maximum value, and which is on the earlier time side of the point representing the maximum value, or the loss angle δ curve does not have a point representing the maximum value, and has a descendingly behaving section in which the loss angle δ value becomes 5° or more smaller at a slope of -1.4°/minute or more.