Patent Description:
In additive manufacturing processes, creating a strong bond between two polymer components can be problematic due to relatively low surface energies of the polymer components. Industry standards employ methods such as solvents, diffusion techniques, heat staking, cross-linking, and ultrasonic welding. However, these techniques are both expensive and time consuming.

Instead, many methods employ simple adhesive methods, such as epoxy, olefin, or methacrylate. Adhesive-based bonds between polymer components, while inexpensive, have marginal adhesion and are generally low strength bonds. Adhesive-based polymer bonds can be aggravated by surface contaminates such as grease, processing debris, dirt, or oil. Thus, adhesive-based bonds between polymer components are generally weak and can weaken over time.

Some techniques use surface preparation, such as plasma etching, exposure to an open flame, or acid etching. These surface preparation techniques can help to some degree, but these processes further add cost to the method and will degrade over time, resulting in a weak bond between polymer components. There is no simple, affordable method that creates improved performance of adhesively bonded polymer joints.

<CIT> discloses a method for manufacturing three-dimensional objects using segmental prototyping.

<CIT> discloses a connection system which includes a first adhesion segment, on which a first planar bonding region is formed; a second adhesion segment, on which a second planar bonding region is formed, which is shaped so as to be complementary to the first planar bonding region, and a solidifiable, liquid bonding substance.

<CIT> discloses repair methods which utilize additive manufacturing for rotor blades and components.

<CIT> discloses an adhesively bonded engine intake manifold assembly.

<CIT> discloses imageable seamed intermediate transfer belts having a large seam surface area, and marking machines that use such imageable seam intermediate transfer belts.

A method of bonding polymer components according to claim <NUM> includes additively manufacturing a first polymer component having a first mating feature, additively manufacturing a second polymer component having a second mating feature, the second mating feature designed to fit with the first mating feature, and joining the first and second polymer components with an adhesive to form a mechanical lock wherein the mechanical lock comprises the first mating feature, the second mating feature and the adhesive.

A polymer article according to claim <NUM> includes a first polymer component having a first surface and an edge, the first polymer component comprising a first mating feature on the first surface, a second polymer component having a second surface and an edge, the second polymer component comprising a second mating feature on the second surface, and a mechanical lock between the first polymer component and the second polymer component. The mechanical lock includes the first mating feature fitted to the second mating feature by an adhesive.

Adhesive-based bonds between polymer components can be strengthened through mechanical locks. Appropriately shape features on surfaces of the polymer components can enhance the bond strength and integrity by creating mechanical locks that work in conjunction with an adhesive. These surface shapes can also distribute stressors on edges of polymer components that would normally cause peeling at a bond site.

<FIG> are schematic drawings of a mechanical lock bond between two polymer components in different embodiments. In article 10A of <FIG>, bond <NUM> connects first polymer component <NUM> and second polymer component <NUM>. Polymer components <NUM>, <NUM> are made through additive manufacturing or <NUM>-D printing techniques, and have low surface energy. Surface energy determines the strength of adhesive attractions. The higher the surface energy, the stronger the adhesive bond, and the closer a substrate material draws an adhesive to it. The lower the surface energy, the weaker the attractive forces in the adhesive bond. Surface free energy for polymers difficult to adhesively bond can range between -<NUM> mN/m for polycarbonate to -<NUM> mN/m for polyhexylmethacrylate.

Bond <NUM> in <FIG> is an adhesive bond enhanced by a mechanical lock. Bond <NUM> includes adhesive gap <NUM> between two mating features: insert feature <NUM> and protruding feature <NUM>. Adhesive gap <NUM> is filled by adhesive <NUM>. Adhesive <NUM> is an epoxy, olefin, or methacrylate used to fill adhesive gap <NUM> between first polymer component <NUM> and second polymer component <NUM>. Adhesive <NUM> can be a neat adhesive (without a filler material) or a reinforced adhesive (such as an epoxy with a filler material to enhance adhesive properties).

Polymer components <NUM> and <NUM> have low surface energy. This makes adhesive bonds between components <NUM> and <NUM> problematic and susceptible to weakening. Protruding feature <NUM> and insert feature <NUM> create a mechanical lock in bond <NUM> that works in conjunction with adhesive <NUM> to hold together polymer components <NUM> and <NUM>. Protruding feature <NUM> and insert feature <NUM> have undercut features <NUM> which provide more stability to the mechanical lock.

Undercut features <NUM> can have a variety of shapes, such as corrugated walls, dovetail shapes, or helical threads. In <FIG>, features <NUM>, <NUM>, are nested mating features with undercut walls that create a mechanical lock. The use of insert feature <NUM> allows bond <NUM> to benefit from a mechanical lock in addition to an adhesive when joining polymer components <NUM> and <NUM>. Features <NUM> and <NUM> can be tailored to address tension, shear, torsion, and edge peel present in joints between polymer components <NUM> and <NUM>. <FIG> shows bond <NUM>, that is similar to bond <NUM> in <FIG>, but increases the number of grooves in undercut feature <NUM> on insert feature <NUM>.

When features grown with additive manufacturing, such as features <NUM> and <NUM>, are added to components <NUM>, <NUM> of article <NUM>, the strength of the bond between components <NUM> and <NUM> is strengthened through a mechanical lock. The complex undercut wall structure of undercut features <NUM> create more surface area for adhesive <NUM> to bond to, strengthening the adhesive bond in addition to providing a mechanical lock to counteract shear forces.

The mechanical lock of <FIG> is made through an additive manufacturing or <NUM>-D printing technique. As polymer components such as <NUM> and <NUM> are created through normal additive manufacturing processes, undercut features can be directly grown on polymer components.

<FIG> are schematic drawings of recessed undercuts on two polymer components creating a mechanical lock bond. In article <NUM> of <FIG>, recessed feature <NUM> is present on both first polymer component <NUM> and second polymer component <NUM>. Recessed features <NUM> create a mechanical lock between polymer components <NUM>, <NUM>, and are both filled with adhesive <NUM>. When adhesive <NUM> is cured, it creates a mechanical lock in conjunction with features <NUM>. Undercuts used to create a mechanical lock, such as undercuts <NUM> in recessed feature <NUM>, can be linear or curved, and may follow a planar or non-planar surface. Additionally, a radius feature on external edges or internal corners of undercut grooves can be created to further mitigate stress concentrations on adhesive materials and polymer components.

Mating features creating mechanical locks can include recessed features, such as grooves and void spaces in conjunction with protruding features, such as pins and blades. Various embodiments of these undercut features are illustrated in <FIG>.

<FIG> are schematic drawings of a mechanical lock in the polymer article <NUM> bond between first polymer component <NUM> and second polymer component <NUM>, in a pinhole configuration. First polymer component <NUM> contains a mating feature in the form of void spaces <NUM>. Second polymer component <NUM> contains a different mating feature in the form of protruding pins <NUM> which are fitted to void spaces <NUM> on first polymer component <NUM>. Void spaces <NUM> and pins <NUM> are created through additive manufacturing or <NUM>-D printing. Both pins <NUM> and void spaces <NUM>, contain complex wall undercut structures. The complex wall undercut structures can be linear or curved grooves, spiral patterns, corrugated walls, dovetail shaping, or helical threads. The array of pins <NUM> fitted in void spaces <NUM>, as shown in <FIG>, creates a mechanical lock between an adhesive and polymer components <NUM>, <NUM>.

<FIG> are schematic drawings of a mechanical lock bond in article <NUM> between two polymer components in a recessed blades configuration. First polymer component <NUM> contains recessed blades <NUM>. Second polymer component <NUM> contains raised blades <NUM> which are fitted to recessed blades <NUM> on first polymer component <NUM>. The mating features, recessed blades <NUM> and raised blades <NUM>, are created through additive manufacturing or <NUM>-D printing. Both raised blades <NUM> and recessed blades <NUM> contain complex wall undercut structures. In this embodiment, a concentric pattern on recessed blades <NUM> on first polymer component <NUM> creates a mechanical lock with raised blades <NUM> on second polymer component <NUM>.

<FIG> are schematic drawings of a mechanical lock bond between two polymer components in a ring-blade configuration. Article <NUM> shows a joint between two polymer components. First polymer component <NUM> contains a mating feature of recessed rings <NUM>. Second polymer component <NUM> contains a mating feature of raised rings <NUM> that fit with recessed rings <NUM> on first polymer component <NUM>. Recessed rings <NUM> and raised rings <NUM> are created through additive manufacturing or <NUM>-D printing. Both raised rings <NUM> and recessed rings <NUM> contain complex wall undercut structures. The extended surface area of the complex wall undercut structures helps an adhesive create a strong bond between both first polymer component <NUM> and second polymer component <NUM>. The combination of an adhesive with mating features <NUM>, <NUM> and undercuts creates a mechanical lock for polymer components <NUM>, <NUM>.

The proposed bond creates an enhanced joint between polymer components with both a mechanical lock and adhesive for overall durability and longer lifespan. This allows for significant improvement in strength and reliability of adhesive bond joints between difficult to bond materials, such as low energy polymer components.

Additionally, this feature reduces sensitivity of polymer component joints to contamination by reliance on mechanical locking in addition to adhesives. Thus, if an adhesive is degraded through outside contamination such as oil, debris, or dirt, a mechanical lock still holds polymer components in place.

The mechanical locking undercut features further simplify assembly accuracy, due to the self-locating nature of matching undercut features on polymer component surfaces. This is particularly true when a protruding feature is matched with a recessed feature. Overall, this allows for strong, reliable, large polymer structures comprised of multiple small components.

<FIG> is a schematic drawing of a peel-resistant edge bond between two polymer components. Article <NUM> includes first polymer component <NUM> and second polymer component <NUM>, joined by bond <NUM>. Bond <NUM> includes adhesive gap <NUM> filled with adhesive <NUM>, and features <NUM>. Bond <NUM> mechanically locks, working in conjunction with adhesive <NUM> to maintain a connection between polymer components <NUM>, <NUM>.

Additionally, article <NUM> contains bumper region <NUM>. Bumper region <NUM> includes edge protective bumper <NUM>, buried taper <NUM>, and tapered edges <NUM>. Typically, when two or more polymer components are connected with an adhesive, edges of the polymer components "peel" away from each other. Bumper region <NUM> is designed to prevent edge peel. Tapered edges <NUM> prevent some peel by avoiding the use of sharp edges on components <NUM>, <NUM>; and bumper <NUM> further protects polymer components <NUM>, <NUM> from peeling away from adhesive gap <NUM> by providing a physical barrier. Buried taper feature <NUM> reduces stress on bond <NUM>. Overall, article <NUM> contains the mechanical lock undercut feature that allows for a strong bond and protected edge.

The proposed polymer surface geometry allows for mechanical locking of polymer components in conjunction with an adhesive bond. This configuration strengthens bonding between polymer components, increases lifespan of bonds, and allows polymer component joints to withstand tension, shear, torsion or edge peel forces.

The method includes additively manufacturing an undercut wall structure on the first mating feature.

The method includes additively manufacturing an undercut wall structure on the second mating feature.

The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
Additively manufacturing a first polymer component having a first mating feature comprises additively manufacturing a recess into the first polymer component.

Additively manufacturing a second polymer component having a second mating feature comprises additively manufacturing a protrusion onto the second polymer component, the protrusion configured to mate with the first mating feature.

Additively manufacturing a second polymer component having a second mating feature comprises additively manufacturing a recess into the second polymer component.

Additively manufacturing a first polymer component having a first mating feature comprises additively manufacturing a void space; and wherein additively manufacturing a second polymer component having a second mating feature comprises additively manufacturing a projection, the projection complementing the void space.

Additively manufacturing a first polymer component having a first mating feature comprises additively manufacturing a recessed blade; and wherein additively manufacturing a second polymer component having a second mating feature comprises additively manufacturing a raised blade, the raised blade fitted to the recessed blade.

Additively manufacturing a first polymer component having a first mating feature comprises additively manufacturing a recessed ring; and wherein additively manufacturing a second polymer component having a second mating feature comprises additively manufacturing a raised ring, the raised ring fitted to the recessed ring.

A polymer article according to claim <NUM> includes a first polymer component having a first surface and an edge, the first polymer component comprising a first mating feature on the first surface, a second polymer component having a second surface and an edge, the second polymer component comprising a second mating feature on the second surface, and a mechanical lock between the first polymer component and the second polymer component including. The mechanical lock includes the first mating feature fitted to the second mating feature by an adhesive. The polymer article includes an undercut wall structure configured to increase the surface area of the first mating feature.

The polymer article of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
The first mating feature comprises a recess.

The second mating feature comprises a protrusion configured to mate with the first mating feature.

The second mating feature comprises a recess.

The first mating feature comprises a void space and the second mating feature comprises a protrusion.

The first mating feature comprises a recessed blade and the second mating feature comprises a raised blade.

The first mating feature comprises a recessed ring and the second mating feature comprises a raised ring.

The polymer article includes a bumper connected to the edge of the first polymer component and connected to the edge of the second polymer component.

The edges of the first and second polymer components are tapered.

The polymer article includes a first buried taper adjacent to the edge of the first polymer component, and a second buried taper adjacent to the edge of the second polymer component.

Claim 1:
A method of bonding polymer components comprising:
additively manufacturing a first polymer component (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) having a first mating feature (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>);
additively manufacturing a second polymer component (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) having a second mating feature (<NUM>, <NUM>, <NUM>, <NUM>), the second mating feature (<NUM>, <NUM>, <NUM>, <NUM>) designed to fit with the first mating feature (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>); and
joining the first and second polymer components (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) with an adhesive (<NUM>, <NUM>) to form a mechanical lock wherein the mechanical lock comprises the first mating feature (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>), the second mating feature (<NUM>, <NUM>, <NUM>, <NUM>) and the adhesive (<NUM>, <NUM>, <NUM>),
characterized in that said method further comprises:
additively manufacturing an undercut wall structure (<NUM>) on the first mating feature and additively manufacturing an undercut wall structure on the second mating feature,
and manufacturing an edge protective bumper (<NUM>), buried taper (<NUM>) and tapered edges (<NUM>).