Blow-molded panel and manufacturing method for blow-molded panel

A method of manufacturing a blow-molded panel, comprising steps of:

• (a) heating a first polymer and a second polymer until said first and second polymers are in a fluid state, wherein said first polymer layer is made of high density polyethylene and said second polymer layer is made of a mixture of metallocene polyethylene and calcium carbonate or a mixture of metallocene polyethylene and glass fiber;
• (b) extruding said first and second polymers to form first and second polymer layers respectively;
• (c) fusing said first and second polymer layers with each other in an overlapping manner to form a fused body;
• (d) blow molding said fused body to form first and second panel members which are spaced apart with each other to form a cavity between said first and second panel members, wherein each of said first and second panel members is constructed by said first and second polymer layers;
• and
• (e) forming a plurality of supporting structures by concurrently stretching and recessing a plurality of different portions of said first polymer layer and a plurality of different portions of said second polymer layer of said second panel member into said cavity for ensuring no additional material of said second panel member being added to form said supporting structures, wherein said supporting structures are extended to bias against said first panel member so as to support said first panel member.